bluuebunny/crossref_metadata_2025 huggingface dataset:
New analysis of the density effects observed on the rotational line profile of induced spectra of H2 and D2 dissolved in argon
Authors: Buontempo U. , Codastefano P. , Cunsolo S. , Dore P. , Maselli P.
Published: April 2011

The induced rototranslational absorption spectra of H2 and D2 dissolved in argon have been measured at T = 165 K at different densities up to about 650 amagats. These new and accurate measurements allow us to derive reliable experimental profiles for the single rotational line. From the induced dipole moment autocorrelation function as obtained from the experimental profile, we have derived a characteristic time suitable to parametrize the density narrowing of the spectral lines. We show how using this new analysis we can solve the inconsistencies and the ambiguity found in previous works on the narrowing effect. The main features of the narrowing phenomena are discussed with the help of simple models.
Properties of sintered submicron copper and silver powders and their relation to low temperature heat exchangers
Authors: Robertson R. J. , Guillon F. , Harrison J. P.
Published: April 2011

Measurements of surface area, porosity, electrical resistivity, and Young's modulus of sintered copper and silver submicron powders with packing fractions in the range 32–54% are reported. These parameters are of value in the design and understanding of sintered heat exchangers for the cooling of liquid helium into the millikelvin temperature range. The surface area and porosity measurements support a model in which the open pores are represented by orthogonal cylinders. This model is particularly well suited to describing heat flow in liquid helium in the pores of the sinter. From the residual electrical resistivity, the thermal conductivity κ of the sinter was calculated to vary between κ/T ~ 0.2 and 2 W∙m−1∙K−2 over the range of packing fractions from 32 to 50%. These conductivities are comparable to the conductivity of either pure 3He or dilute 4He – 3He mixtures in the open pores of the sinter. The elastic constant of the sinter varied from ~ 1 to 12% of that of the bulk metal over the range of packing fractions. By treating the sinter as an effective or composite medium for phonons with wavelengths larger than the pore or particle size, the elastic constant measurements support the possibility of there being a very large density of phonon states in the frequency range that would be excited at millikelvin temperatures. These modes could be important in the heat exchange between liquid helium in the pores of the sinter and the electrons in the metal powder.
Oscillations in an acoustooptic bistable device
Authors: Chrostowski J. , Delisle C. , Tremblay R.
Published: April 2011

A study of an acoustooptic bistable device operating as a self-sustained generator is presented. The frequency of oscillation can be altered by an external voltage.
Direct measurements of N2 broadened linewidths in the CO fundamental at low temperatures
Authors: Bouanich J.-P. , Farrenq R. , Brodbeck C.
Published: April 2011

The halfwidths of CO vibration–rotation lines, pressure-broadened by N2 have been measured in the fundamental band at −83, −148, and −180 °C, using a variable temperature absorption cell and a high resolution spectrometer. The temperature dependence of linewidths has been calculated from the Anderson–Tsao–Curnutte theory and compared to the experimental determinations.
Relativistic effects in the photoionization of hydrogenic ions
Authors: Goldman S. P. , Drake G. W. F.
Published: April 2011

Accurate relativistic calculations of the oscillator strength densities and photoeffect cross sections for neutral hydrogen and hydrogenic lead (Z = 82) are performed up to the high energy region. Relativistically induced Cooper minima are found in the partial wave contributions at high energies. The results are in good agreement with calculations in which the scattering continuum is represented by a discrete relativistic variational basis set.
Self-consistent approximations and the Legendre transform
Authors: Kunstatter G. , Revzen M. , Trainor L.
Published: April 2011

It is well-known in quantum field theory and statistical physics that the effective action (i.e., the Legendre transform of the free energy) is the generating function for one particle irreducible diagrams. We present an explicit diagrammatic proof of this result which permits a clear statement concerning its validity in the context of self-consistent approximation schemes. In particular, we find a necessary and sufficient condition on the approximate set of Green's functions for the Legendre transform theorem to hold. This condition is exactly what one expects on physical grounds. Our proof also lends itself to an examination of more extended diagrammatic schemes, such as those involving composite operators in renormalization theory.
Tc of intermediate coupling superconductors with a variable electronic density of states (EDOS)
Authors: Ashraf M. , Carbotte J. P.
Published: April 2011

Using the model of Leavens and Carbotte for intermediate coupling superconductors, we have derived and evaluated analytical expressions for the critical temperature Tc, and the zero temperature gap Δ0 of those superconductors with a variable electronic density of states (EDOS). EDOS is given by a Lorentzian peak superimposed on a constant background with the chemical potential falling at some arbitrary position within the peak. The most significant modifications occur for a narrow Lorentzian with the peak close to the Fermi level. The value of the dimensionless ratio 2Δ0/kBTc remains close to the Bardeen–Cooper–Schrieffer (BCS) value of 3.53. Also, the present calculation compares very favourably with a previous exact calculation.
Theory of resonance fluorescence from a gas of identical two level atoms
Authors: Zaidi H. R.
Published: April 2011

A Green's function formulation of the problem of resonance fluorescence from a system of identical two level atoms is presented. The general formulation is suitable for the investigation of a variety of nonlinear phenomena, e.g., propagation of electromagnetic waves inside the medium, fluorescence from a finite medium, optical bistability, atomic correlations, and additional side bands. Translational motion, collisions, Coulomb dipole–dipole interaction, excitation transfer, and local field corrections are also included in the basic equations. The effect of atom–atom correlations in the relaxation mechanism (radiative or collisional) is also taken into account. Finally, the results are also presented in the "generalized dressed atom" (GDA) representation. Applications of the general theory will be given in a future paper.
Fluid spheres in Einstein–Yukawa theory
Authors: Krori K. D. , Bhattacharjee R. , Chaudhury Sumita , Barua Madhumita
Published: April 2011

We present here a complete solution (to a certain order of approximation) of fluid spheres in the Einstein–Yukawa theory. It is nonsingular and satisfies physical conditions (positive pressure and density). The solution has some relevance to neutron stars.
Vibrational population distribution in the hydroxyl night airglow
Authors: Turnbull D. N. , Lowe R. P.
Published: April 2011

Relative populations of the vibrational levels ν = 2 to ν = 9 (except ν = 5) of the hydroxyl radical have been determined from observations of the Δν = 2 and 3 sequences of the vibration–rotation bands in the infrared night airglow spectrum using a Fourier transform spectrometer. The observed line intensities were corrected for water vapour absorption using a new technique. The results indicate a population of the upper vibrational levels which is as much as a factor of two lower than that found in other studies. The observed distribution is not consistent with the atomic hydrogen ozone reaction being the sole excitation mechanism in the night airglow unless the quenching and other rates used in our model are in error.
The a3Π1–X1Σ+ emission system of CBr+
Authors: Tsuji Masaharu , Shinohara Keiji , Mizuguchi Toshinori , Nishimura Yukio
Published: April 2011

The visible emission spectrum of the CBr+ molecule has been observed for the first time in the helium afterglow reaction of CBr4. It was excited by the dissociative charge-transfer reaction of He+ with CBr4 at thermal energy. The vibrational analysis led to the following spectroscopic constants (in cm−1).[Formula: see text]
The ν13 fundamental band of benzene
Authors: Plíva Josef , Johns J. W. C.
Published: April 2011

The perpendicular band of the E1u vibration ν13 of benzene, occurring near 6.7 μm, has been measured on a BOMEM high-resolution Fourier transform spectrometer with a 246 cm optical path difference. The observed linewidth (full width at half height) of ~ 0.0048 cm−1 was reduced by deconvolution to ~ 0.0020 cm−1, which is slightly below the Doppler limit. The dense rotational structure was well resolved, and it was possible to assign over 125 subbands in the region 1466.5 to 1503 cm−1. A perturbation, identified as a third-order Jx,y-Coriolis interaction with a state located only ~ 0.055 cm−1 above the fundamental (presumably the A2u component of ν4 + 2ν20), causes distortion of the rotational structure and formation of subband heads in the low-KpQ-branches, which exhibit a striking line-like shape. The spectrum was analyzed in detail with the aid of the computer program SYMTOP for the treatment of symmetric top bands whose upper states are involved in arbitrary interactions. The Hamiltonian included, in addition to the Jx.y -Coriolis perturbation, the l-type resonance [Formula: see text]. A set of accurate spectroscopic constants was obtained for the perturbed ν13 upper state. Using these constants, 2750 lines of the ν13 band, which could be assigned nonzero weights, were reproduced with an overall standard deviation of ~ 0.00046 cm−1.
Utilisation d'une ligne de microphotodiodes en spectroscopie dispersive : application à la détection du NO2
Authors: Bures Jacques , Leonard François , Monchalin Jean-Pierre
Published: April 2011

A self-scanned photodiode array has been used as a multiplex sensor for laboratory detection and measurement, by dispersive spectroscopy, of trace quantities of the atmospheric pollutant NO2. The on-line data acquisition and numerical analysis system allows in particular to eliminate some systematic errors and drifts (Taylor filtering) and the noise associated with high spatial frequencies (low-pass filtering). We have then been able to show that an absorption spectrum, corresponding to low absorber concentrations, has a sufficient information content for the characterization of the pollutant and the measurement of its concentration (ppm m), even when noise and drifts are present. The proposed system can be favorably compared to the ones, based on a single photoelectric detector, which are commercially used.
Far infrared spectra of amorphous-Si:H thin films on polyethylene
Authors: Mathur M. S. , Card H. C. , Kao K. C. , Mejia S. R. , Tabisz G. C.
Published: April 2011

Hydrogenated amorphous-silicon thin films (a-Si:H) were deposited by microwave plasma chemical-vapour decomposition of SiH4, on thin polyethylene sheets. The high-resolution, far infrared measurements were performed on these films in the 700–50 cm−1 region on a Nicolet far infrared interferometer. The use of polyethylene as the substrate material permitted the determination of the absorption bands at 656.4, 652, 639.4, and 543 cm−1 with a shoulder at 539 cm−1 and a broad feature at 70.8 cm−1. These features provided evidence for SiH, SiH2 (as predicted by Lucovsky et al.), and SiH3 combinations in the film, as well as far more complex systems.
Télémètre à détection coherente avec un laser CO2 à ondes entretenues : étude et conception
Authors: Vincent Denis , Otis Gabriel
Published: April 2011

We performed a theoretical and experimental study of a 10.6 μm heterodyne detection system with nonlinear postdetection. A single laser serves as both transmitter and local oscillator; the intermediate frequency is given by the Doppler effect due to a rotating target. An electrooptic crystal modulates the amplitude of the laser beam at a frequency of 15 kHz; a synchronous voltmeter measures the return signal after the nonlinear element. Values of the signal-to-noise ratio with respect to incident optical power agree with the results of the theoretical model. In particular, experimentally measured target-induced frequency spreading effects on the signal-to-noise ratio correspond to the predictions of the model. We also describe an experimental system.
Nouvelles conditions aux limites exactes pour les champs électromagnétiques à la surface des matériaux absorbants
Authors: Langlois Pierre , Boivin Alberic
Published: April 2011

Recent experiments using laser light by Langlois et al. have shown for the first time that actual diffraction patterns from edges do depend on the material and ridge shape of the scatterer, as well as on the polarization of the incident wave. These results have brought out the inadequacy of the scalar diffraction theory for diffraction angles larger than about 1°. Farther out one must use exact electromagnetic theory, with the attendant requirement that exact boundary conditions be known for the fields on the surface of the scattering object. These boundary conditions are well known for perfect conductors (Neumann's or Dirichlet's conditions) or even for good conductors (Leontovich's conditions). However, in the visible range one finds that copper is not a good conductor. Therefore, we develop in the present paper new exact boundary conditions, which generalize those of Leontovieh. In actual fact our new boundary conditions have enabled us to perform edge diffraction calculations for a considerably larger range of complex refraction indices covering the materials used. More generally one may claim that our boundary conditions do apply for all usual materials (copper, aluminium, ebonite … ), in as much as they are absorbing and the local ridge curvature of the scattering objects is far larger than the wavelength.
Configurations, performance, and applications of biconical taper optical fibre coupling structures
Authors: Kawasaki B. S. , Johnson D. C. , Hill K. O.
Published: April 2011

The configurations and performance of fused biconical taper optical fibre couplers are summarized. Their application to passive multiterminal networks is considered and the practical limitations of these networks resulting from the properties of the couplers are discussed.
Design of a narrow-band reflection IR multilayer
Authors: Zheng Shu-Ying , Lit John W. Y.
Published: April 2011

This paper describes a design method for a narrow-band reflection filter with metal layers. The principle used is the theory of induced transmission, with the help of graphic displays. The conditions, at which the maximum values of the reflectance, the potential transmittance, and the energy transmittance of the filter occur simultaneously when the absorptance reaches a minimum at the design frequency, are described. Several designs of high reflection filters with narrow bandwidths in the IR region are presented.
Lidar measurements of the atmosphere
Authors: Carswell Allan I.
Published: April 2011

Lidar systems are now widely used for diagnostics of the atmosphere. These systems employ the backscattering of laser radiation to provide information on atmospheric parameters via a number of scattering and absorption processes. The field has progressed rapidly in recent years and many high-performance lidar systems are now in operation around the world. These systems use lasers in the ultraviolet, visible, and infrared, and are able to make quantitative measurements of many atmopsheric parameters. In this paper the lidar field is reviewed. Present lidar systems are described and the current measurement capabilities are summarized.
Transmission spectra of silver intercalated 2H-TaS2 and 1T-TiS2
Authors: Scholz G. A. , Frindt R. F.
Published: April 2011

The room temperature transmission spectra of Agx TaS2 and Agx TiS2 have been measured in the energy range from about 1.3 to 2.8 eV for various values of x. A rigid band model, where charge transfer from the silver cation to the lowest d conduction band of the host macro-anion occurs, can explain the changes in the spectra. These changes in the transmission spectra provide a direct method for monitoring staging and the intercalation rate of the silver ions.
Nonmetallic behaviour in thin metal wires
Authors: Jain Neeraj , Srivastava Ramji
Published: April 2011

General expressions for the temperature coefficient of resistivity (TCR) of thin metal wires have been derived by incorporating the thermal expansion of the wire diameter and the wire-to-substrate expansion mismatch. A possibility of transition to nonmetallic behaviour is predicted at low temperatures.
Structural changes in the antifluorite crystal (NH4)2SnBr6
Authors: Armstrong Robin L. , Morra Rose M. , Powell Brian M. , Buyers William J. L.
Published: April 2011

A study of structural phase transitions in the antifluorite crystal (NH4)2SnBr6 by nuclear quadrupole resonance and neutron powder diffraction techniques is presented. Interpretation of the bromine nuclear quadrupole resonance spectrum leads to a prediction concerning the nature of the distortions that occur as the temperature is lowered. Profile analysis of neutron diffraction data substantiates the prediction by revealing that the 157 K transition involves the antiferro-rotation of halide octahedra accompanied by a relatively small distortion of the unit cell whereas the 144 K transition involves a further ferro-rotation of the octahedra and a relatively large distortion of the unit cell.
Half shell reaction matrices and high energy phase shifts for the Paris potential
Authors: Matin M. A. , Gandhi Dulal Chandra
Published: April 2011

We have calculated high energy phase shifts for the Paris potential for Elab ≥ 330 MeV and compared these with experimental results for all channels with L ≤ 3. The effect of the momentum dependence on these phase shifts is studied. The half shell reaction matrices for these channels are also presented.
Alpha particle emission from interaction of 19.5 MeV neutrons with 147Sm nuclei
Authors: Dalmas J. , Augustiniak W. , Glowacka L. , Jaskóla M. , Turkiewicz J.
Published: April 2011

The energy distribution and forward–backward asymmetry of α-particles emitted in the 147Sm(n,α)144Nd reaction has been measured at the neutron energy 19.5 MeV. The results have been analyzed in terms of statistical, pre-equilibrium, and knock-on models.
Dipole oscillator strength distributions and related properties for ethylene, propene and 1-butene
Authors: Jhanwar B. L. , Meath William J. , MacDonald J. C. F.
Published: April 2011

Dipole oscillator strength distributions (DOSDs) have been constructed for ground state ethylene, propene, and 1-butene. Each DOSD is constructed by using available experimental and theoretical photoabsorption cross sections and by constraining the resulting dipole oscillator strength data to satisfy the Thomas – Reiche–Kuhn sum rule and molar refractivity constraints. The latter were obtained from experimental refractive index measurements of relevant dilute gases. The recommended DOSDs, and the values of integrated "band" oscillator strengths, and the dipole oscillator strength sums Sk and Lk (for a variety of k values) obtained from them, are reported. The discussion includes an analysis of the reliability of the results using 1-butene as a detailed model.
Comment on effect of tube fluctuations in reptation theory for polymer melts
Authors: Noolandi J. , Bernard D. A.
Published: April 2011

The effect of fluctuations in the tube contour length is considered for the recent reptation model of polymer melt dynamics. The prediction of Doi's theory for the zero shear melt viscosity is evaluated quantitatively, and the exponent of the corresponding power law is found to depend strongly on molecular weight, in disagreement with experiment.
The role of pseudo-eigenvalues of the Boltzmann collision operator in thermalization problems
Authors: Blackmore R. , Shizgal B.
Published: April 2011

The calculation of the eigenvalues of the hard sphere Boltzmann collision operator using discrete matrix methods yields discrete eigenvalues, a large fraction of which are unconverged and lie in the continuum spectrum of the operator. The role of these pseudo-eigenvalues is examined. The results strongly suggest that for practical calculations the rigorous treatment of the continuum is not necessary provided that a moderately large number of pseudo-eigenvalues are included.
Theory of low temperature spin exchange scattering for a physisorbed two-dimensional gas of hydrogen atoms
Authors: Morrow M. , Berlinsky A. J.
Published: April 2011

Calculations are presented of the two-dimensional scattering cross sections which are required to evaluate the longitudinal and transverse relaxation times T1 and T2 and the frequency shift Δν due to spin exchange collisions between H atoms physisorbed on a surface. The results are used to interpret the recent measurements by Crampton and co-workers of the relaxation time T1 for H atoms in the presence of solid H2 walls. New results are also presented for T1, due to three-dimensional scattering in the gas, using a more recent triplet H–H potential than the one previously employed by Berlinsky and Shizgal.
A stochastic approach to the freezing of supercooled liquids
Authors: Das Amal K.
Published: April 2011

We have considered the freezing of a supercooled liquid, in particular water, experimentally found to be describable by the phenomenological deterministic equation dn/dt = κn(1–n), n(t) being the fraction of ice. In order to start the process of nucleation, a white noise fluctuation is invoked. This fluctuation is considered both additively and multiplicatively with respect to the deterministic equation. The mean first passage time, a quantity of direct physical interest, is calculated in both cases. With the multiplicative noise, the Itô–Stratonovich route is avoided through a suitable transformation of the Langevin equation and through the study of the resulting Fokker–Planck equation thereof.
Hodographic study of transverse magnetohydrodynamic flows
Authors: Swaminathan M. K. , Chandna O. P. , Sridhar K.
Published: April 2011

By reducing the order, from two to one, of the linear momentum equations in a steady transverse flow of a viscous electrically conducting fluid, the hodograph method can be applied to obtain a partial differential equation of the stream function as satisfied by the Legendre transform function. The approach is then illustrated by solving four problems.
An optical method for measuring PVT data, critical constants, virial coefficients, and molecular parameters of GeH4
Authors: Balzarini D. , Rosenberg A. , Palffy-Muhoray P.
Published: April 2011

An optical method has been developed for measuring PVT data for a fluid. The method consists of measuring the refractive index as a function of density and temperature and, separately, as a function of pressure and temperature. The results are combined to yield PVT data. Germane has been studied. Isotherms have been measured in the temperature range 293 to 323 K and the density range 0.07 to 0.7 g cm−3. The data in the critical region are analyzed to obtain the critical constants Pc = 48.8 atm, ρc = 0.522 g cm−3, and Tc = 38.97 C ± 0.2. The data at lower densities are fitted to a virial equation of state to obtain the second and third coefficients. The values at 312.15 K are B = −2.37 cm3 g−1 and C = 1.99 cm6 g−2. The data are analyzed to yield the Lennard–Jones parameters ε/K = 230 ± 15 deg and σ = 4.6 ± 0.2 Å.
High resolution absorption and magnetic rotation studies of the system of formaldehyde-d1
Authors: Clouthier D. J. , Craig A. M. , Ramsay D. A.
Published: April 2011

The 410, 430, and 410610 bands of the [Formula: see text] system of HDCO have been reinvestigated in absorption under high resolution. While the results confirm the earlier rotational analyses of Job et al. (1969), arguments are advanced for changing the assignment of the 777 cm−1 interval from ν3′ to ν6′.The bands have also been studied in magnetic rotation. Most of the activity is attributed to the magnetic dipole transition moment between the ground and excited singlet states, but some activity is assigned to singlet–triplet interactions. For the 430 band, a possible mechanism with ΔJ = 0, ΔN = 0, and ΔKa = 0 selection rules has been deduced.
Résolution, par partition de l'espace, des équations de diffusion inelastique en base stationnaire perturbée : analyse critique de la formulation semiclassique
Authors: Jolicard Georges
Published: April 2011

A molecular energy transfer has been studied for a particular system constituted by groups of quasi degenerated levels using a perturbed stationary state formulation. The model resolves, independently in two separate regions of the radial axis, the adiabatic and quasi resonant energy transfer equations. Using the Wentzel–Kramers–Brillouin (WKB) formula, the classical motion equations corresponding to each case are set out in detail.
Entropy measurements on LixTiS2
Authors: Dahn J. R. , Haering R. R.
Published: April 2011

We show how measurements of [Formula: see text] (V = electromotive force, T = temperature) on Li/LixTiS2 electrochemical cells can be used to gain information about the entropy of LixTiS2. Experimental details and results of [Formula: see text] measurements on Li/LixTiS2 cells are reported. The results show that staging, not in plane lithium ordering, is the dominant physical mechanism in LixTiS2. Our data disagree with earlier work by Thompson.
The infrared spectrum of HNO
Authors: Johns J. W. C. , McKellar A. R. W. , Weinberger E.
Published: April 2011

Vibration–rotation spectra of HNO (DNO) have been observed in a flow system following the reaction of hydrogen (deuterium) atoms with NO. The spectra were recorded at approximately Doppler limited resolution with a large Fourier transform spectrometer. Complete analyses have been made of the ν1 bands of HNO and DNO with the following results (in cm−1).[Formula: see text]Spectra of ν2 (NO stretching) were also observed in both HNO and DNO, but ν3 (bending) proved too weak to be detected in either molecule.
A study of high energy hadron–nucleus interactions
Authors: Khushnood H. , Shakeel A. , Ahmad A. , Ahsan M. Z.
Published: April 2011

An attempt has been made to investigate the multiplicity distributions of grey, black, shower, and heavy tracks, the dispersions of their distributions, intercorrelations between them, the dependence of the mean normalized multiplicity on the target mass and energy, etc., in hadron–nucleus interactions at 24, 50, and 400 GeV incident energies. The results obtained in the study reveal that the behaviour of the multiplicity distribution is independent of the nature and energy of the impinging hadron. Furthermore, on redefining the mean normalized multiplicity, it is found to be not only energy independent but also projectile independent, suggesting a new kind of scaling in particle–nucleus interactions.
Two-photon resonant optical processes in atomic potassium
Authors: Zhang P.-L. , Schawlow A. L.
Published: April 2011

Two-photon resonant optical processes, using potassium ns2S1/2 states (7 ≤ n ≤ 20), are investigated in detail by a pulsed dye laser. About 100 coherent lines between 288–422 nm are generated through the processes ωUV ± ωIR = 2ωL and [Formula: see text]. The strongest lines (near mP–4S transitions) are formed by parametric oscillation and are generally split into components that are frequency shifted relative to atomic transitions. About 70 lines are generated by six-wave mixing processes and 15 other lines by four-wave mixing processes. The wavelengths, relative intensities of the lines, and the components of the strongest lines are explained with a theoretical analysis based on the wave equation, atomic polarization, and phase-match condition for both wave-mixing processes and parametric oscillations.
Effect of isotope shifts in the blue–green band spectrum of the lead dimer
Authors: Berg L.-E. , Ismail S. , Klynning L. , Martin H. , Pereira A. , Royen P.
Published: April 2011

The absorption spectrum of gaseous Pb2 has been investigated in the blue – green spectral region. Owing to the overlap between the six dominating isotopic Pb2 molecules formed by natural lead – in combination with the very dense structure of the [Formula: see text] transition – it is impossible to rotationally resolve the Doppler limited spectrum. Still, regions of rotational structure were resolved. These were explained by interference effects between the absorption spectra of the individual isotopic species. The regions of resolved rotational structure form a pattern similar to a moiré pattern. The information gained is used together with laser induced fluorescence data in a reanalysis of the F and X states. The following main molecular constants for the 208Pb2 molecule have been derived (cm−1):[Formula: see text]
Polar modes in molecular crystals: Ewald splitting of infrared and Raman lines
Authors: Valle Raffaele Guido Della , Fracassi Pier Francesco
Published: April 2011

Ewald's long-wave method is applied to long-range electrostatic potentials within the framework of quasi-harmonic lattice dynamics of molecular crystals. The angular dependence of phonon frequencies, transition dipole moments, and polarizabilities of single crystals is derived for all crystallographic species. Analytical expressions for infrared and Raman line shapes in powder samples arc obtained, pointing out the dependence of line shapes on the crystal symmetry and the radiation polarization. The infrared and Raman spectra of polycrystalline HCl are discussed.
The millimetre wave spectrum of the 13C14N radical in its ground state
Authors: Bogey M. , Demuynck C. , Destombes J. L.
Published: April 2011

The N = 0→ 1 and N = 1 → 2 transitions of 13C14N have been observed in a rf glow discharge in a CO + N2 + He mixture cooled at liquid nitrogen temperature. The 41 measured frequencies have been used to determine the rotational and fine structure constants as well as the hyperfine structure due to the 13C and 14N nuclei. Relative line intensities have also been calculated with a view to interstellar detection.
Herzberg–Teller intensity stealing in the 279-nm system of phenylacetylene: Evidence from single vibronic level fluorescence spectra
Authors: Bacon A. R. , Hollas J. M. , Ridley T.
Published: April 2011

Single vibronic level fluorescence spectra, following absorption into bands of the [Formula: see text] system of phenylacetylene, have confirmed this system to be an unusual case of Herzberg–Teller intensity stealing in which the intensity that is vibrationally induced is greater than that which is electronically allowed. The activity of the b2 vibrations ν34 and ν35 in intensity stealing is confirmed, and a large Duschinsky effect affecting these two vibrations has been discovered. In addition, it has been shown that the b2 vibration ν36, which we have newly assigned, is weakly involved in intensity stealing. This observation has led to new assignments of the low wavenumber b1 and b2 vibrations, not only in phenylacetylene, but in benzonitrile also. An interesting Coriolis interaction between the lowest b1 and b2 vibrations in each molecule has been analyzed.
Herzberg's impact on the physics of Rydberg states
Authors: Fano U. , Lu K. T.
Published: April 2011

Mechanisms of the excitation, transformation, and decay of atomic and molecular Rydberg states are described and unsettled questions are discussed.
Spectra and lifetimes of triatomic hydrogen molecules
Authors: Figger H. , Fukuda Y. , Ketterle W. , Walther H.
Published: April 2011

Excited neutral triatomic hydrogen molecules were formed by charge transfer to beams of [Formula: see text], [Formula: see text], D2H+, and H2D+ ions. The density of the molecules generated was high enough to investigate their spectra in the visible region. The lifetimes of some rovibronic states of the neutral molecules were measured from the decrease of the line intensities behind the charge-exchange region.
Study of T2 relaxation for l-doublet transitions of OCS
Authors: Mehrotra S. C. , Mäder H.
Published: April 2011

The pressure dependence of transverse relaxation times T2 has been measured for l-doublet transitions of OCS in the excited vibrational state (01 10) in rotational states with 29 ≤ J ≤ 42 by using the transient emission technique. The line width parameter decreases with an increase of rotational quantum number J from 6.54(12) MHz/Torr at J = 29 to 5.53(6) MHz/Torr at J = 42. The result has been compared with the results obtained from the modified Murphy–Boggs theory.
Tunable diode laser spectra of the ν3−ν1 region of CS2
Authors: Baeten Edith , Blanquet Ghislain , Walrand Jacques , Courtoy C. P.
Published: April 2011

The 850 to 900 cm−1 region of CS2 has been investigated with a tunable diode laser spectrometer having Doppler-limited resolution and a wavenumber accuracy of 10−3 cm−1. More than 2250 lines were detected and attributed to eight transitions of 12C12S2, 12C32S33S, or 12C32S34S.
The structure of fluorene (C13H10) and the fluorine–argon van der Waals complex from a high-resolution near ultraviolet spectrum
Authors: Meerts W. Leo , Majewski W. A. , Herpen W. M. van
Published: April 2011

The high-resolution fluorescence excitation spectrum of the fluorene molecule and its van der Waals complex with argon has been studied. Rotationally resolved spectra were obtained by combining a well-collimated supersonic molecular beam with a single frequency tunable ultraviolet (uv) source. The S1 ← S0[Formula: see text] vibronic transitions in fluorene and fluorine–argon were observed. The rotational constants of both molecules were determined and from these the structure of the fluorine–argon complex has been deduced. The argon atom is located above the middle five-membered ring. The coordinates of the position vector of the argon atom in the complex in the centre-of-mass system of fluorene are r = (3.46 ± 0.03) Å and [Formula: see text]. A model calculation of the fluorine–Ar structure was found to be in quite good agreement with the experimental result. The newly introduced inertial defect of the complex ΔIc = −7(3) amu Å2 provided an experimental measure of the zero-point motion of argon in the complex.
Study of collision-induced rotational perturbations in gases via the wing shape of infrared bands
Authors: Bulanin M. O. , Tonkov M. V. , Filippov N. N.
Published: April 2011

A theoretical analysis of the infrared absorption band wings is presented. The wing shape is expressed in terms of the spectral density of rotational perturbations experienced by absorbing molecules in moderately dense gases. The developed formalism is applied to the absorption in the high-frequency wing of the ν3 CO2 band. Analytical approximation of the experimental rotational perturbation densities is used to deduce the rotational relaxation parameters as well as the mean square torques, which provide information on the short-range anisotropic intermolecular interactions.
On the H− migration in the ion
Authors: Kalcher J. , Rosmus P. , Quack M.
Published: April 2011

For the [Formula: see text] ion, the geometries and energies of several minima, and barriers between these, have been calculated from correlated self-consistent electron pair (SCEP) and coupled electron pair (CEPA) electronic wave functions. The spectroscopic and kinetic implications of the potential energy surface are discussed in terms of its molecular symmetry group.
Rotational perturbations and the Zeeman effect in the band of HCF
Authors: Suzuki Tetsuo , Saito Shuji , Hirota Eizi
Published: April 2011

The dye laser excitation spectrum of the [Formula: see text] vibronic band of HCF was observed between 18 190 and 18 422 cm−1 with Doppler-limited resolution. The observed spectrum exhibits a number of anomalies. The perturbations observed for Ka = 1 levels are well explained by an electronic Coriolis interaction with highly excited vibrational levels of the ground electronic state. Other anomalies are difficult to analyze, because most of them are local without showing any systematic frequency shifts. Some of the perturbed lines are found to have large Zeeman effects; thus the perturbations are ascribed to interactions with the lowest triplet state. The rotational analysis of the observed spectrum leads to the following molecular constants for HCF in the Ã1A(010) state: ν0 = 18 298.6927(71), B + C = 2.26710(34), B − C = 0.074(15), and the electronic Coriolis coupling term [Formula: see text], all in cm−1 with standard errors in parentheses.
Rydberg levels of the sodium atom and the ammonium radical calculated by perturbation theory
Authors: Havriliak Stephen , Furlani Thomas R. , King Harry F.
Published: April 2011

Rydberg levels of sodium and the ammonium radical have been computed by second-order Rayleigh–Schrödinger perturbation theory with the frozen-core model defining the zero-order problem. Very extensive basis sets are used. From the sodium atom study, we determine the contributions of f- and g-type functions to the pair correlation energies and use this information to correct for basis set deficiencies as well as higher perturbation corrections in the molecular problem. The theory supports Watson's assignment of the Schüler band as being the analogue of the sodium D line, and implies that this is also the most likely assignment of the Schuster band.
Vibrational dependence of electronic nonradiative processes in the state of and
Authors: Winkoun D. , Chapoulard D. , Dujardin G. , Leach S.
Published: April 2011

Vibrational mode selective, radiationless transitions have been sought in the [Formula: see text] states of [Formula: see text] and [Formula: see text] by determining the radiative kr(ν′) and nonradiative knr(ν′) rates of electronic relaxation of energy selected vibronic levels of these cations. The relaxation rates were derived from measurements of ion fluorescence quantum yields and lifetimes using a photoelectron-fluorescence photon delayed coincidence apparatus, described in the text, in which the ions are formed by direct photoionization. Mode selective behavior is confirmed for the ν1 and ν2 modes of the [Formula: see text] state of [Formula: see text], previously studied by a threshold photoelectron-fluorescence photon coincidence method in which photoion formation involved auto-ionization as well as direct photoionization. In the case of the ν3 and ν4 modes of [Formula: see text], knr(ν′) was found to depend only on the excess energy Eν′ in the [Formula: see text] state and not on the particular mode optically excited. The absence of mode selectivity in this cation could be due to very rapid vibrational redistribution, but more probably results from similar-valued nonradiative coupling matrix elements of vibronic levels involving ν3 and (or) ν4 modes for a given value of Eν′. This is shown to be consistent with the known spectroscopic properties of [Formula: see text].
High-resolution Fourier transform study of the ν11 and ν7 fundamentals of cyclopropane
Authors: Pliva Josef , Johns J. W. C.
Published: April 2011

The absorption spectrum of cyclopropane, C3H6, was measured in the region between 790 and 950 cm−1 on a high-resolution Fourier transform spectrometer. The section containing the Q-branches of the perpendicular band of the ν11 vibration of species E′ was deconvolved to an effective line width of 0.0020–0.0025 cm−1. The structure of the ν11 band is strongly affected by l-type resonance. A total of 88 sub-bands with KΔK = −42 to 45 have been assigned in this band. The K = 4–3 and 2–3 sub-bands both exhibit K doubling of the lines with high J resulting from a combined effect of the off-diagonal matrix elements [Formula: see text], [Formula: see text], and [Formula: see text] with the l doubling in the K = 1, l = 1 state. Otherwise, the ν11 band is found to be free of perturbations by other vibrational states, in spite of the fact that a Jx,y Coriolis interaction is allowed by selection rules with the ν7 band (species [Formula: see text]) whose band origin is only 14.38 cm−1 below that of ν11. This shows that the value of [Formula: see text] is essentially zero. Also, the allowed Jz Coriolis interaction with the ν10 state, which lies 160.01 cm−1 above ν11, does not noticeably affect the two bands. A Hamiltonian matrix, including the matrix elements responsible for the K doubling and l-type resonance, was used for the treatment of the ν11 band. A set of accurate ground state constants and spectroscopic constants for the upper state ν11 is reported that reproduces 3240 observed lines of this band with a standard deviation of 0.0009 cm−1. Lines of the parallel band ν7 are just barely seen between the ν11 lines, which are perhaps 30–50 times stronger. Spectroscopic constants for the ν7 band have been obtained from 135 individual lines assigned to the Q- and R-branches of sub-bands with K = 6–21.
Summary of group theoretical results for microwave and infrared studies of H2O2
Authors: Hougen Jon T.
Published: April 2011

Group theoretical treatments found in the literature for other molecules, based on double-groups of appropriate permutation–inversion groups, are modifed slightly and applied to H2O2. This permits a more unified view of many theoretical results derived in various earlier studies of the molecule. Briefly, if no effects due to internal rotation tunneling were observed in the H2O2 spectrum, the molecule could be treated using the C2 point group of its equilibrium geometry. If effects due to internal rotation tunneling through only the trans barrier are observed (as is presently the case), the molecule should be treated using the C2h point group of its trans planar conformation at the top of the tunneling barrier. If effects due to internal rotation through both the trans and cis barriers can be detected, it will be necessary to treat the molecule using a double group [Formula: see text] of the C2h, point group. Vibrational, torsional, and rotational basis function symmetry species, energy level diagrams, selection rules for electric dipole transitions and perturbations, etc. are presented here for the [Formula: see text] double group, but these results can easily be converted to those for the C2h point group by dropping all s and d subscripts. An empirically discovered successful fitting procedure for the ground state rotational levels, reported in a treatment of microwave and millimetre wave measurements on H2O2, can be rationalized on the basis of the present theoretical results.
Absorption bands of O2 and OH in a new ultraviolet continuum and in the XeCl laser spectrum
Authors: Shimauchi M. , Oikawa K.
Published: April 2011

Two excimer lasers of the automatic pre-ionization type have been constructed. To avoid impurities, the two series of condensers were placed outside the discharge chamber. Using one of these devices we have observed a new ultraviolet (UV) continuum from a discharge through a He–O2 mixture at 900 Torr. The continuous nature of this emission was assured by the observation of almost 80 absorption bands of the O2 Schumann-Runge system arising from highly excited vibrational levels and of some OH bands in the A–X system. The same type of discharge through pure He emits no continuum but some OH bands. The time dependence of the light pulses was studied to infer the origin of the continuum. Based on these observations, we show that the strong absorption in the B–X, 0–2 band of the XeCl laser is due to the P11, Q13, and Q13′ lines in the 0–0 band of the OH A–X system; the estimated intensity of this absorption amounting to 5–7% of the total intensity of the XeCl laser. The XeCl spectra were photographed on an E1 quartz spectrograph and in the third order of a 6.65 m grating.
The infrared spectrum of CS
Authors: Winkel Jr. R. J. , Davis Sumner P. , Pecyner Rubén , Brault James W.
Published: April 2011

The infrared emission spectrum of carbon monosulfide was observed as a sequence of vibration–rotation bands in the X1Σ+ state, with strong heads of the Δν = 2 sequence degraded to the red. Eight bands of 12C32S were identified, and bands corresponding to the isotope 12C34S were also observed. The most prominent band head, that of the (2–0) band, is at 2585 cm−1, with the other heads spaced approximately 26 cm−1 to smaller wavenumbers. Our data, taken with the Fourier transform spectrometer at the National Solar Observatory (Kitt Peak) include the first reported laboratory observations of the band heads and as many as 200 lines in each band. These observations allowed the calculation of vibrational and rotational constants to higher order than previously reported.
Lambda doubling in the infrared spectrum of SH
Authors: Winkel Jr. R. J. , Davis Sumner P.
Published: April 2011

The (1–0), (2–1), and (3–2) infrared vibration–rotation bands of the X2Π ground state of sulfur monohydride were observed in emission from a furnace. Multiplet splitting produces two subbands, each of which exhibits lambda splitting. The band heads were observed for the first time, 285 lines were measured, and a calculation of lambda-doubling parameters was made. The spectrum was recorded using the Fourier transform spectrometer at the National Solar Observatory (Kitt Peak).
Rotational analysis of the laser excitation spectra of the bromoacetylene and deuterobromoacetylene cations
Authors: King Michael A. , Maier John P. , Misev Liubomir , Ochsner Martin
Published: April 2011

High-resolution laser excitation spectra of the [Formula: see text] bands of the bromo- and deuterobromoacetylene cations have been recorded and rotationally analyzed. The new data are compared with those for the neutral molecule and discussed in terms of electronic structure.
High resolution vacuum ultraviolet absorption spectrum of N2: Perturbations in the and c4(0) 1Πu Rydberg levels
Authors: Yoshino K. , Freeman D. E.
Published: April 2011

High resolution absorption spectra of N2 in the wavelength region 85.73–86.65 nm have been photographed at a reciprocal dispersion of 0.03 nm/mm in the second order of a 2400 line/mm grating by a 6.65 m vacuum spectrograph. The Rydberg transitions [Formula: see text] and [Formula: see text] are analyzed. Gross irregularities in line positions and intensities are interpreted in terms of homogeneous and heterogeneous perturbations among the vibronic levels c4(0), [Formula: see text], b′(18), b(22), b(23), and b(24). A multilevel deperturbation procedure is applied to these levels to produce deperturbed spectroscopic constants. The perturbation matrix elements with the largest values are those of the homogeneous interactions [Formula: see text] and c4(0) × b(23) = 7.3 cm−1, and that of the heterogeneous interaction [Formula: see text]. Term values established for the upper levels c4(0) and [Formula: see text] of the vacuum ultraviolet (VUV) bands are combined with the recent results of Suzuki and Kakimoto for the visible bands c4(0)–a″(0) and [Formula: see text] to obtain term values of the [Formula: see text] level.
Electric dipole moment of X2Π OH and OD in several vibrational states
Authors: Peterson K. I. , Fraser G. T. , Klemperer W.
Published: April 2011

Dipole moments are measured for OH (2Π) in the ν = 0, 1, and 2 vibrational states and for OD in the ν = 0 and 1 states using the molecular beam electric resonance technique. These are listed in the table below.[Formula: see text]A very accurate value of 0.00735(7) D is obtained for the difference in dipole moments between the ν = 0 and 1 vibrational states of OH. This is within 20% of the best theoretical results. The dependence on vibrational state is very nonlinear, which is also in agreement with theoretical results. Finally, the difference between the ν = 0 dipole moments of OH and OD is close to the expected value.
Rotational bands in the nucleus 168Er and some remarks on their interpretation
Authors: Davidson W. F. , Dixon W. R. , Storey R. S.
Published: April 2011

Further analysis of previously published data on 168Er, together with results of new measurements of selected portions of the neutron capture γ-ray spectrum, has resulted in the construction of an improved level spectrum for this nucleus. Altogether 127 excited levels have now been established and grouped into 36 rotational bands. Some remarks on their interpretation are advanced.