bluuebunny/crossref_metadata_2025 huggingface dataset:
A measurement of the lambda-type doubling spectrum of the CH radical by microwave-optical double resonance: further characterization of the A2Δ state
Authors: Brazier Christopher R. , Brown John M.
Published: April 2011

Several lines in the lambda-doubling spectrum of the CH radical in its ground 2Π state have been recorded by the technique of microwave-optical double resonance. Individual lines in the (0, 0) band of the A2Π–X2Π system at 431 nm were pumped with a dye laser and the absorption of microwave radiation was detected as an increase in the level of fluorescence. The microwave transition frequencies were measured to an accuracy of 0.1 MHz and the results were used to determine values for the lambda-doubling parameters in the molecular effective Hamiltonian. Several lines in the (0, 0) band of the A–X system were also recorded with sub-Doppler line widths using the saturation technique of intermodulated fluorescence. The proton hyperfine structure was easily resolved. The very small effects of lambda-doubling in the A2Δ state were also detected for the higher rotational levels by precise measurement of the laser induced fluorescence spectrum. The values obtained for the parameters that described these effects in the molecular Hamiltonian are discussed.
Experimental determination of the 1Σ+ state electric dipole moment function of carbon monoxide up to a large internuclear separation
Authors: Chackerian Jr. C. , Farrenq R. , Guelachvili G. , Rossetti C. , Urban W.
Published: April 2011

Experimental intensity information is combined with numerically obtained vibrational wave functions in a nonlinear least-squares fitting procedure to obtain the ground electronic state electric dipole moment function of carbon monoxide valid in the range of nuclear oscillation (0.87–1.91 Å) of about the V = 38th vibrational level. Vibrational transition matrix elements are computed from this function for ΔV = 1, 2, 3 with V ≤ 38.
Rotational perturbations in the CN(B2Σ+–X2Σ+) tail band system. III. Molecular constants for the 4Π, 4Σ+, A2Πi, and X2Σ+ states
Authors: Ito Haruhiko , Ozaki Yasushi , Nagata Takashi , Kondow Tamotsu , Kuchitsu Kozo
Published: April 2011

The CN(B2Σ+–X2Σ+) tail band system was observed by using the dissociative excitation reactions of HCN and BrCN with Ar(3P0.2) in an argon flowing afterglow. The following intensity anomalies owing to the B2Σ+ ~ 4Π rotational perturbations were analyzed: (νB, ν11) = (9,x), (11,x + 2), and (18,x + 13), where x is estimated to be 0 or 1. These anomalies, as well as(νB, ν11) = (12,x + 3), (14,x + 6), and (17,x + 11), were analyzed by spectral simulation. The CN(B2Σ+–X2Σ+) 14–14 band spectrum observed by Jenkins was re-analyzed, and the molecular constants for the perturbing 4Π state, the interaction constants, and the crossing schemes for the B2Σ+ ~ 4Π perturbations were determined. The intensity anomalies due to the perturbations by the 4Σ+, A2Πi, and X2Σ+ states were also observed: (νB, νΣ) = (15,p + 6), where p is estimated to be 8 ± 1, (νB, νA) = (11, 26) and (17, 34), and (νB, νX) = (11, 28). The molecular constants for the perturbing levels were estimated by a simulation analysis.
Rotational line strengths in a 5Σ – 5Π transition with application to the A – X system of CrO
Authors: Sassenberg U. , Cheung A. S.-C. , Merer A. J.
Published: April 2011

Detailed calculations of the line strengths in a 5Σ – 5Π transition as a function of J show that the relative branch intensities in the A – X system of CrO, which do not follow the published formulae for 5Σ(b) – 5Π(a) transitions, can be explained very well in terms of strong spin uncoupling in the 5Π state, with a single perpendicular transition moment dominating. It is emphasized that spin uncoupling affects line strengths by an amount that increases very rapidly with multiplicity, so that algebraic formulae for the pure coupling cases quickly lose their value. An unusual cancellation effect occurs in the main branches of a 5Σ – 5Π transition, nine of which have intensities that drop to zero and then rise again with increasing J.
Radiative charge transfer and radiative association of helium ions with neon atoms
Authors: Cooper D. L. , Kirby K. , Dalgarno A.
Published: April 2011

Ab initio calculations are carried out for the dipole moments of the X2Σ+, A2Π, and B2Σ+ states of HeNe+, and the transition dipole moments connecting them. The effects of spin-orbit interactions are explored briefly. The transition dipole moments are used in a calculation of the rate coefficients of radiative charge transfer and radiative association of He+ ions in neon and the associated spectra are obtained. Comparison with experimental data provides support for the conclusion that the radiation detected was emitted in the course of the collisions of He+ with Ne. Some quantitative discrepancies remain which may arise from intensity stealing by the A22Π1/2 state from the X2Σ+ state.
Vacuum ultraviolet laser spectroscopy: I. Fluorescence studies of the B′2Δ state of NO
Authors: Banic J. R. , Lipson R. H. , Stoicheff B. P.
Published: April 2011

Individual rotational levels of the B′2Δ state (ν′ = 1 – 8) of nitric oxide have been excited using tunable, coherent, vacuum ultraviolet radiation (in the range 140–170 nm) generated by four-wave mixing in magnesium vapour. Excitation spectra have also been obtained for the F2Δ, N2Δ, D2Σ+, E2Σ+, and M2Σ+ Rydbcrg states. Time-resolved fluorescence intensity measurements of rotational levels in ν′ = 1, 2, 3, 5, and 8 of the B′2Δ state indicated single-exponential decay over a large pressure range, resulting in average lifetimes of ~225 ns. Rotational levels in ν′ = 4, 6, and 7 displayed non-single-exponential decay. This behaviour is attributed to enhanced collisional population transfer from the B′2Δ state to the F2Δ and N2Δ states as a result of strong interaction amongst these states.
The Lyman and Werner bands of H2
Authors: Dabrowski I.
Published: April 2011

The Lyman and Werner bands of H2 have been measured under high resolution in the vacuum ultraviolet from 1000 to 1650 Å. Flash discharge spectra, both in absorption and in emission, have allowed an extension of the analysis to include most of the rotation–vibration levels of the ground state ([Formula: see text], ν = 0 to 14, J = 0 to 29). The C1Πu state has been observed from ν = 0–13, and the [Formula: see text] state from ν = 0–17, including highly rotationally excited levels for ν = 0–6. The resulting rotation–vibration energy levels are accurate to 0.1 cm−1.The agreement between observation and ab initio theory is now very good. The deviations of the vibrational levels are very close to zero for low ν, but increase to 0.3 cm−1 for high ν. The ab initio calculations are somewhat less accurate for the rotational levels. The deviations are close to zero for low J, but increase to 4 cm−1 for high J, that is, for energy levels close to the dissociation limit. It can also be seen that the convergence error in the Born–Oppenheimer calculation is small (~0.1 cm−1) at low energies, but approaches 1 cm−1 near the dissociation limit.
High resolution emission spectrum of H2 between 78 and 118 nm
Authors: Roncin Jean-Yves , Launay Françoise , Larzilliere Michel
Published: April 2011

The complete high resolution emission spectrum of molecular hydrogen is obtained for the first time in the range 78–118 nm. A uniform set of data is derived from accurate line positions of the (unperturbed) Q branches of the C, D, D′, and [Formula: see text] transitions. Molecular constants fitted for both the ground state and the excited states of symmetry [Formula: see text] are obtained. For the latter case, they are compared with ab initio and multichannel quantum defect theory (MQDT) calculations. Self-absorption features indicate the production, in an appreciable amount, of H2(ν″ = 1) in the discharge. The reported data were not available to laser physicists and also astrophysicists who have observed strong emission lines of H2 from the atmospheres of Jupiter and Saturn.
The I1Πg state of hydrogen: adiabatic corrections, energy levels, L uncoupling, and electronic transition moments
Authors: Dressler K. , Wolniewicz L.
Published: April 2011

Employing Kołos and Rychlewski's ab initio wave functions for the electronic I1Πg. state of molecular hydrogen (Dieke's 3dπ 3E) we calculated the diagonal corrections for nuclear motion to the electronic energies over the internuelear-distance range R = 1 – 12 au. The vibration–rotation energy levels calculated in the adiabatic approximation are compared with spectroscopic results in H2, HD, and D2 and it is concluded that the convergence error of the electronic energy in the inner well [Formula: see text] of the double-minimum potential curve is 1.0 ± 0.5 cm−1. The electronic matrix elements of angular-momentum coupling with the [Formula: see text] state and of the dipole transition moments to the (B, B′) [Formula: see text] and C1Πu states are also presented.
Ab initio calculation of properties of the neutral diatomic hydrogen molecules H2, HD, D2, HT, DT, and T2
Authors: Hunt J. L. , Poll J. D. , Wolniewicz L.
Published: April 2011

Adiabatic values for a selection of energy levels and matrix elements of the quadrupole moment and the polarizability of H2, HD, D2, HT, DT, and T2 are presented. Additional energy levels and matrix elements are available for a minimal charge upon request from the Depository of Unpublished Data, C.I.S.T.I., National Research Council of Canada, Ottawa, Ont., Canada K1A 0S2.
Microwave-optical double resonance of HNO in the Ã1A″(000) state
Authors: Petersen J. C. , Saito S. , Amano T. , Ramsay D. A.
Published: April 2011

Twenty-nine rotational transitions of HNO in the Ã1A″(000) excited state have been measured by microwave-optical, and radio-frequency-optical double resonance spectroscopy. Most of the observed lines are found to be perturbed by a few to a few hundred MHz. Improved values have been obtained for the rotational constants B and C and for the centrifugal distortion constant δJ. MODR lines have also been observed between levels of the Ã1A″ excited state, high rovibronic levels of the [Formula: see text] ground state, and levels of the ã3A″ state. One of the lines shows a larger magnetic effect, suggesting a perturbation by a level of the ã3A″ state.
Herzberg continuum cross section of oxygen in the wavelength region 193.5–204.0 nm and band oscillator strengths of the (0, 0) and (1, 0) Schumann–Runge bands
Authors: Cheung A. S.-C. , Yoshino K. , Parkinson W. H. , Freeman D. E.
Published: April 2011

Cross sections of oxygen at 300 K have been obtained from photoabsorption measurements at various pressures, from 50 to 760 Torr (1 Torr = 133.3 Pa), at wavelength intervals of 0.0002 nm throughout the region 193.5–204.0 nm with a 6.65-m photoelectric scanning spectrometer equipped with a 2400 line/mm grating and having an instrumental full width at half maximum of 0.0013 nm. The spectral features contributing to absorption in this region are the discrete lines of some Schumann–Runge bands and underlying dissociation continua consisting of the weak Herzberg continuum of O2 and a pressure dependent continuum involving two molecules of O2. Analysis of the pressure dependence of the total continuum cross section in window regions between the discrete lines yields the Herzberg continuum cross section, which decreases monotonically from 1.4 × 10−21 cm2 at 193.58 nm to 5.1 × 10−24 cm2 at 204.06 nm. At all wavelengths in this region, our values of the Herzberg continuum cross section are smaller than previous laboratory values, much smaller than the values used in many photochemical stratospheric models, and consistent with recent in situ stratospheric cross-section measurements. The acceptance of reduced Herzberg continuum cross sections significantly affects photochemical modelling predictions. Band oscillator strengths f(0, 0) = 2.95 × 10−10 and f(1, 0) = 3.13 × 10−9 of the (0, 0) and (1, 0) Schumann–Runge bands have been determined by direct numerical integration of the measured discrete cross section remaining after subtraction of the continua from the total cross section. Improved wavenumber measurements of the (0, 0) and (2, 1) Schumann–Runge bands are given.
The Ã1A″(S1) excited electronic states of HCN and DCN: Isotopic evidence that unifies experiment and theory
Authors: Bickel G. A. , Innes K. K.
Published: April 2011

High-resolution vacuum ultraviolet absorption spectra of D13CN and DC15N are photographed, especially for comparison with the so-called β–X system, observed previously for DCN but not for HCN. Isotopic shifts establish the absolute vibrational numbering for this system, yielding its assignment to the [Formula: see text] transition. The measured bands between 53 100 and 65 200 cm−1 are thereby accommodated by a single electronic transition as predicted by ab initio theory. Constants of all three Ã-state vibrations of HCN and each DCN are determined for the first time.
High-resolution emission bands of the A2Π – X2Π system of SO+
Authors: Hardwick J. L. , Luo Yin , Winicur D. H. , Coxon J. A.
Published: April 2011

The A2Πi → X2Πr visible band system of SO+ has been recorded photographically at high resolution. Molecular constants for the A and X states have been fitted to the measured line positions of the 0–5, 0–6, 1–5, and 1–6 bands. Λ-type doubling was resolved completely for most of the lines of the 2Π1/2 – 2Π1/2 sub-bands, and has led to the first reported values of the splitting constants p′ and p″. All the estimated constants have been merged with constants obtained previously from medium-resolution spectra for other levels of the X2Π ground state. A self-consistent set of constants is reported for ν′ = 0 and 1 and for ν = 4–9, together with revised equilibrium constants.
An ab initio investigation of the potential function and rotation–vibration energies of NH3
Authors: Bunker P. R. , Kraemer W. P. , Špirko V.
Published: April 2011

Fifty-four points on the potential energy surface of the ground electronic state of the ammonia molecule, with energies up to 9700 cm–1 above equilibrium, have been calculated ab initio using the configuration interaction technique. An analytic potential function has been fitted through these points and the rotation–vibration energy levels have been calculated using the nonrigid invertor Hamiltonian. The agreement with experiment is satisfactory enough that the anharmonic force constants obtained can be realistically used to assist in the interpretation of anharmonicity effects in the spectrum. We calculate the equilibrium bond length as 1.016 Å, the equilibrium HNH angle as 106.2°, and the invertion barrier as 1995 cm−1.
The ν1 and v5 bands of D2CO and improved ground state constants
Authors: Clar H.-J. , Yamada K. , Birss F. W. , Winnewisser G. , Gush H. P.
Published: April 2011

The symmetric and antisymmetric C—D stretching vibrations of D2CO, the ν1 and ν5 fundamental bands, have been measured with high-resolution spectrometers. The region near the origin of the ν1 band, 2026–2087 cm−1, has been recorded by a tunable, diode laser spectrometer with Doppler-limited resolution and an accuracy of about 0.001 cm−1. The measurements were extended to the region between 2000 and 2300 cm−1 using a BOMEM Fourier transform spectrometer at the University of British Columbia. The limit of instrumental resolution was 0.004 cm−1.About 600 lines were assigned to the ν1 fundamental band and more than 1000 to the ν5 band. The band origins were found at ν1 = 2060.917 cm−1 and ν5 = 2162.922 cm−1. From the assigned transitions in the ν1 and ν5 bands, infrared combination differences for the ground state have been performed. By fitting the 1230 combination differences simultaneously with the published microwave data, we have achieved a complete set of very accurate molecular parameters for the ground vibrational state of D2CO.Both excited states ν1 = 1 and ν5 = 1 were found to be strongly perturbed by other states owing to Fermi and Coriolis interactions. Thus, only rough estimations for the rotational constants of these states can be given. Possible interactions will be discussed.
Internal rotation, Stark effect, and rotational magnetic moments in CH3CD3
Authors: Ozier Irving , Meerts W. Leo
Published: April 2011

Ethane-1,1,1-d3 has been studied by the electric-resonance molecular-beam method. By anticrossing techniques, the zero-field energy differences for J = 1 and 2 have been measured corresponding to the normally forbidden selection rules (J ↔ J), [Formula: see text], and [Formula: see text]. From these splittings, three splitting ratio measurements, and four existing R-branch microwave frequencies, determinations were made of the moment of inertia of the CH3-top Iα = 3.1549(12) amu Å2 and of the effective height of the threefold barrier to internal rotation V3 = 1004.13(21) cm−1, as well as of B and several distortion constants. From the current CH3CD3 value of V3 together with previous values for asymmetrically deuterated forms of ethane, it has been shown that the change of V3 with deuteration is −3.05(13) cm−1 per deuteron. By conventional beam methods, the Stark and Zeeman effects have been studied. The Stark measurements have been analysed in terms of the anisotropy [Formula: see text] in the polarizability and the effective dipole moment for the matrix elements diagonal in J, namely μQ = μ0 + μJJ(J + 1) + μKK2. It has been found that μ0 = 0.0108617(5) D, μJ = 0.809(53) μD, μK = −2.06(10) μD, and [Formula: see text] = 0.672(27) × 10−24 cm3. The two molecular g factors have been measured, [Formula: see text] and [Formula: see text], and the anisotropy [Formula: see text] magnetic susceptibility has been evaluated.
Dye laser and thermal emission spectroscopy of the TbO molecule
Authors: Kulikov N. , Kaledin L. A. , Kobyliansky A. I. , Gurvich L. V.
Published: April 2011

The rotational structure of six bands of the TbO molecule, including the 0–0 bands of electronic transitions III, IV, and V, was analyzed using laser excitation spectroscopy with selective fluorescence detection. From the fluorescence spectra obtained through excitation of selected rotational lines in these bands, the energies of 14 low-lying Ω states as well as ΔG1/2 values for the four lowest Ω states were determined. The values of Ω and rotational constants B and D were found for each, low-lying state and the upper states of the analyzed bands; an energy linkage for all the electronic transitions, whose rotational structure has been analyzed, is established. The ground state constants of TbO are (2σ—uncertainty in parentheses) Ω = 6.5, B0 = 0.3525(1) cm−1, D0 = 1.8(2) × 10−7 cm−1, ΔG1/2 = 837.1(1) cm−1, α = 1.5(1) × 10−3 cm−1.
The infrared spectrum of the ν2 fundamental band of the molecular ion
Authors: Watson J. K. G. , Foster S. C. , McKellar A. R. W. , Bernath P. , Amano T. , Pan F. S. , Crofton M. W. , Altman R. S. , Oka T.
Published: April 2011

The observation and analysis of 46 lines of the infrared ν2 band of the [Formula: see text] molecular ion are described. The data include 16 new observations as well as the 30 previously published lines. The spectra are observed in absorption in a hydrogen discharge using tunable monochromatic sources, either a laser difference-frequency system or a diode laser. Two modulation techniques, either discharge amplitude modulation or Doppler velocity modulation, are used to increase the sensitivity. Ground state combination differences between the observed lines are in good agreement with ab initio calculations, and scaled ab initio rotational term values are used to relate the different K-energy stacks. Padé-type expressions are found useful in representing the line frequencies, and 44 lines are fitted by 23 parameters with a standard deviation of 0.014 cm−1. The two lines omitted appear to be perturbed by a rovibrational interaction between the ν2 and ν1 states that should become more important for higher values of J.
The state of I2: Analysis by quantum simulations of bound-free D → X fluorescence
Authors: Tellinghuisen Joel
Published: April 2011

The McLennan bands of I2 represent the highly structured diffuse emission from high ν′ levels of the ion-pair D state to the vibrational continuum of the ground state. A variety of existing data are analyzed together with quantum simulations of D → X spectra to yield an improved description of the D state, including an estimate of the internuclear distance, Re = 3.576 ± 0.015 Å, and a determination (within 1 unit) of the vibrational numbering of ν′ levels accessed in D ← X absorption at room temperature.
A simplified optical model description of heavy ion fragmentation
Authors: Townsend L. W. , Wilson J. W. , Norbury J. W.
Published: April 2011

The fragmentation of 213 MeV/nucleon 40Ar ions by 12C targets is described within the context of a simple abrasion–ablation fragmentation model. The abrasion part of the theory utilizes a quantum-mechanical formalism based upon an optical model potential approximation to the exact nucleus-nucleus multiple-scattering series. The ablation stage of the fragmentation is treated as a compound nucleus evaporation. The decay probabilities for the various particle emission channels are computed using the EVAP-4 Monte Carlo computer program. Predictions for production cross sections for isotopes of sulfur, phosphorus, silicon, and aluminum are made and compared with experimental data. The model is also used to compare predicted and experimental element production cross sections for 1.88 GeV/nucleon 56Fe colliding with 12C and 208Pb targets.
A reexamination of the Green function treatment of the Mollow problem
Authors: Hutchinson D. A.
Published: April 2011

The application of the Green function method to the Mollow problem is reconsidered. This problem consists of an intense monochromatic electromagnetic field in resonance with a two-level atom. We obtain a solution to the infinite hierarchy of Green function equations of motion instead of decoupling the equations of motion. This solution gives an excitation spectrum in agreement with Mollow's results. We conclude that earlier discrepancies in the excitation spectrum were artifacts of the decoupling procedure. Finally, we comment upon the physical ideas associated with the present and previous Green function treatments of the Mollow problem.
Comment: On the derivation of coupled cluster equations
Authors: Paldus J. , Čížek J.
Published: April 2011

The derivation of an explicit form of the coupled cluster equations using the time-independent formalism and its various aspects are discussed in view of a recent derivation given by Dabrowski. Various earlier derivations are compared as well as different requirements needed in nuclear and molecular or atomic applications.
Estimates of eē production from nuclear muon capture
Authors: Beder Douglas
Published: April 2011

Motivated by the experimental search for μ−A → e−A, we calculate [Formula: see text], which provides a small background of high-energy electrons, limiting experimental sensitivity. A reasonable extrapolation to the nuclear case, for a Ti target, indicates an effective background for Ee > 95 MeV of approximately 2 × 10−12 (branching ratio to total capture rate).
Test of the charge density wave model of potassium
Authors: Coulter P. G. , Datars W. R.
Published: April 2011

Predictions of the charge density wave (CDW) model for potassium are tested by high-field induced torque experiments. The CDW model is described to show the open orbits on the Fermi surface of potassium with a CDW. Expressions for the induced torque are developed in terms of the resistivity and other parameters of the sample. The induced torque as a function of magnetic field direction shows sharp structure above 3–4 T with more than 20 peaks in 180° rotation. The peaks have the character of open orbits and the large number is predicted by the CDW model. The magnetic field, sample orientation, and temperature dependences of induced torque are also investigated. The magnetic field dependence agrees with that expected from open orbits with magnetic breakdown. However, the open orbits that would cause the induced torque peaks are not in directions predicted by the CDW model. Variation of induced torque with temperatures between 1.4 and 2.1 K can be explained by some of the features of the model although the observed changes are larger than those predicted. The conclusion is that the CDW model explains many of the properties of the high-field induced torque structure.
The effect of van der Waals complexes on the longitudinal proton spin relaxation time in hydrogen–argon gas mixtures
Authors: Lemaire Claude , Armstrong Robin L.
Published: April 2011

An extensive set of measurements of the proton spin longitudinal relaxation time T1 for molecular hydrogen diluted in argon is presented. These measurements, carried out at 18.975 MHz, establish the temperature and density dependence of the relaxation time from 110 to 300 K and from 2 to 100 amagat, respectively. The T1 data, although taken in the intermediate density regime in which binary collisions lead to a characteristic linear dependence on density, ρ, exhibit a significant nonlinear dependence. This effect is attributed to the presence of van der Waals complexes (H2–Ar dimers) in the mixture and is explained as a consequence of the formation and annihilation dynamics of the dimers. A theoretical model is developed which accounts for all qualitative aspects of the data. The dimer contribution to the relaxation time is described in terms of two parameters: the dimer annihilation cross section σ and the equilibrium constant K describing the relative number of H2–Ar dimers. The cross section σ is very nearly equal to the geometric cross section. The constant K is of the order of 10−23 cm3 and in good agreement with the theoretical value. Its variation with temperature is predicted well by our calculations.
Thermooptical effects observed in CdSxSe1−x semiconductor doped glasses
Authors: Thibault G. , Denariez-Roberge M.-M.
Published: April 2011

Thermooptical effects have been found to play an important role in CdSxSe1−x semiconductor doped glasses. The laser energy absorbed by the semiconductor microcrystals increases the local temperature of the glass, thus changing the optical properties of the medium. A thermal model has been developed to explain the experimental hysteresis curves and some other transient effects.
An examination of the sensitivity of the forward-scattering spectrum from Pyrex fibers
Authors: Racey T. J. , Rochon P.
Published: April 2011

Rayleigh's equations are shown to provide a very good model for the forward-light-scattering spectra of ≈30-μm Pyrex fibres. The irradiance pattern is shown to be uniquely matched over the 10° scattering range of the experiment, producing values for the diameter and index of refraction that are good to better than 0.1% and 0.03% respectively. The extreme sensitivity of this technique is examined to show why it is so difficult to match irradiance patterns over such large ranges of scattering angle.
Propriétés spatiales et temporelles des résonateurs lasers munis de miroirs à conjugaison de phase
Authors: Bélanger P. A. , Paré C. , Piché M.
Published: April 2011

The properties of laser resonators with one phase-conjugate mirror are reviewed. All these resonators are geometrically stable; their resonant frequencies are determined by the frequencies of the pump waves, while the spacing between the satellite resonant frequencies is fixed by the cavity length. Their diffraction losses are higher on the phase-conjugate mirror than on the conventional mirror. Phase-conjugate resonators are less sensitive to intracavity aberrations than conventional resonators. They can be used for short-pulse compression when the phase-conjugate mirror is produced by degenerate four-wave mixing in a nonlinear medium with pump waves consisting of mode-locked pulse trains. [Translated by the journal]
Spectral-narrowing techniques for excimer laser oscillators
Authors: McKee Terrence J.
Published: April 2011

Various techniques for use in spectral narrowing and tuning of excimer laser oscillators are described. Intracavity dispersive elements include Littrow grating, grazing-incidence grating, prisms, and Fabry–Perot etalons. Recent developments to improve overall efficiency and reduce broadband noise are outlined.
Étalonnage des lunettes autocollimatrices par interférométrie en lumière laser
Authors: Bouillon Gratien , Tremblay Gilles , Moisan Jacques , Delisle Claude
Published: April 2011

Calibration of autocollimators is usually done using a sine bar. In this paper we describe an interferometric method in which only conventional metrological laboratory equipment is used, namely an helium–neon laser and a Michelson interferometer. The precision obtained is comparable for both interferometric and sine-bar methods. For comparison purposes, a very simple third calibration method has also been used. Here, a previously calibrated autocollimator serves as the reference. [Translated by the journal]
Scatter plate interferometer using two correlated diffusers
Authors: Kothiyal M. P. , Grover C. P. , Delisle C.
Published: April 2011

A scatter plate interferometer that uses two discrete correlated diffusers as a scatter plate is described. The diffusers consist of mirror images of a speckle distribution.
Bistability, optical regenerative oscillations, and chaos in an integrated acoustooptic device
Authors: Jerominek H. , Delisle C. , Pomerleau J. Y. D. , Tremblay R.
Published: April 2011

Optical bistability experiments have been performed using an integrated acoustooptic modulator by making use of a surface acoustic-wave delay line in the feedback loop. Different experimental results are reported, including optical hysteresis, differential gain, and oscillatory behaviour. Possible modifications of the acoustooptic integrated bistable device are also proposed.
Caractéristiques de la décharge d'un laser à argon multiwatt continu
Authors: Breton J.-L. , Bédard G.
Published: April 2011

We report on the construction of a 10-mm bore 60-W continuous wave argon ion laser operated at a discharge power of about 64 kW, which provides a continuous current of 200 A. Specially designed high-current-density anodes and cathodes are described. Experimental results on the effects of an axial magnetic field (0–875 G) on discharge parameters are also presented.
Optical equiphase filter approximation using segments of straight lines
Authors: Lévesque M. , April G. , Arsenault H. H.
Published: April 2011

Phase filters may be used to modify the phase distribution on a wave front in order to correct distortions on the wave front or to create arbitrary phase distributions. Under certain conditions, the phase filter may be made by plotting the equiphases of the complex amplitude as lines of equal width, which may be done with a simple digital plotter. Such equiphase filters cause two types of problems: the overlapping of diffraction orders and the additional aberrations introduced when the equiphases are approximated by segments of straight lines plotted by a computer. The parameters that determine the useful field of the filtered phase distribution and the aberrations introduced by the filter are used to obtain an expression for the optimum length of the straight line segments that approximate the curved equiphases.
Laurent-series expansions for the finite Hankel self-transforms
Authors: Boivin Richard , Boivin Albéric
Published: April 2011

Two simple representations in terms of power series are obtained for the eigenfunctions of the finite Hankel transformation. In each case the series coefficients are shown to satisfy a three-term, numerically stable recurrence formula. Expressions are provided for normalizing the coefficients and extending the eigenfunctions beyond the unit interval.
Image diffractionnelle due à une pupille aberrante non-uniforme
Authors: Villeneuve Jean-Eudes , Biswas Subhash C. , Boivin Albéric
Published: April 2011

The problem of diffraction by a nonuniform pupil exhibiting residual aberrations has been studied theoretically. A simple and elegant solution of the problem has been obtained. This solution is valid for the case where a circularly symmetrical pupil filter is used in conjunction with an optical system having spherical aberration, primary coma, curvature, or distorsion. The analytical expressions of that solution can be evaluated numerically with remarkable simplicity. Results for a few optimum apodizers and primary coma are presented in graphical form and discussed.
Relaxation of thermal lenses in a liquid crystal film
Authors: Fuh Y. G. , Code R. F.
Published: April 2011

The transient thermal-lens effect produced by a pulsed laser in a 6CB nematic liquid crystal film containing a small amount of an absorbing dye is considered. A suitable time-dependent model for the thermal-lens effect is presented. The analysis leads to a simple way of determining the principal thermal-diffusion constants in nematic liquid crystal materials.
Electromagnetic diffraction of a transversal two-dimensional Gaussian beam at normal incidence on an absorbing circular cylinder
Authors: Langlois P. , Boivin A. , Lessard R. A.
Published: April 2011

We present the exact electromagnetic solution to the diffraction problem of a transversal two-dimensional Gaussian beam at normal incidence on an absorbing circular cylinder. The direction of constant amplitude for this Gaussian ribbon is perpendicular to the cylinder's axis. The results are valid in the Fresnel region as well as in the far field, and can be applied to actual values of the complex index of refraction for current-absorbing materials at optical frequencies (conductors or dielectrics). The diffracted field is expressed in terms of two cylindrical Gaussian edge waves arising from each "side" of the circular cylinder.
III–V compound semiconductors for communications
Authors: Dyment J C.
Published: April 2011

III–V compound materials (such as GaAs, AlAs, InP, and their alloys) possess several unique properties that are ideally suited for the construction of novel light-emitting, detector, and transistor structures. Some of the key properties as well as the status of new crystal-growth techniques for III–V materials may be summarized as follows:alloys can be grown with continuous variation of bandgap (Eg) and index of refraction (n);the mobilities (μe) can be significantly higher than in silicon;the development of MBE, VPE, and MOCVD crystal growth techniques have enabled the sequential deposition of layers ≤10 nm in thickness with sharp interfaces (≤2 nm) between layers;highly uniform layers can now be grown over 5-cm dimensions with control of thickness and composition to better than a few percent.This paper reviews how these III–V material properties and crystal-growth techniques can be combined to achieve state-of-the-art laser, detector, and transistor devices.After reviewing the performance of these discrete devices, the progress achieved to date towards combining these elements to form optoelectronic integrated circuits (OEIC's) will be reviewed. Potential applications for both the discrete and integrated formats will be discussed.
Metalorganic chemical-vapour-deposition growth and characterization of GaAs
Authors: Blaauw C. , Miner C. , Emmerstorfer B. , Springthorpe A. J. , Gallant M.
Published: April 2011

GaAs epitaxial layers have been grown on semi-insulating GaAs substrates using the technique of metalorganic chemical-vapour deposition. The organometallic compounds trimethylgallium and trimethylgallium–trimethylarsenic adduct were used as source reagents for gallium, whereas arsine and trimethylarsenic were used as sources for arsenic. Photoluminescence measurements at 8 K indicated that carbon was present in the layers as the dominant background acceptor, in most cases, and to a lesser extent copper (Cu) and manganese (Mn) acceptors were also present. Secondary-ion mass spectroscopy (SIMS) analysis confirmed the presence of these acceptors. Silicon was also identified by SIMS in most layers. The concentration of Cu and Mn was correlated with the starting substrate and with the deposition parameters (growth rate, deposition temperature). It was also found that their concentration in the epitaxial layers could be reduced by a careful heat-treatment and chemical etch prior to epitaxial growth.
Propriétés électriques de l'arséniure de gallium dopé à l'étain, déposé par épitaxie en phase vapeur à partir d'organometalliques
Authors: Roth A. P. , Beckett D. , Sundaram V. S. , Yakimova R.
Published: April 2011

The carrier mobility has been measured between 10 and 300 K in epitaxial layers of Sn-doped GaAs grown by metalorganic vapor-phase epitaxy (MOVPE). Experimental and calculated values are compared to obtain the compensation ratios. It is shown that above 77 K the experimental mobility can be calculated in a satisfactory way only by including scattering by localized potential centers.
Photoresistive measurement of liquid-encapsulated Czochralski GaAs
Authors: Berolo O.
Published: April 2011

Wafers cut from undoped GaAs single crystals, grown by the liquid-encapsulated Czochralski (LEC) method, are used as semi-insulating substrates for the fabrication of planar, ion-implanted devices and circuits. As the dimensions of these structures are reduced, the effect and distribution of crystal defects and dislocations become relevant to device reproducibility and yield over the whole wafer.A nondestructive technique has been developed for the evaluation of sheet-resistance of commercially grown LEC GaAs semi-insulating wafers. The "dark-spot" technique, utilized by Blunt, has been modified to give a topographical representation of the sheet resistance distribution of semi-insulating GaAs wafers. This is achieved by illuminating the wafer with a thin light strip and defining a dark-spot with a cursor placed perpendicular to the strip. As the illuminated strip is believed to consist of material two orders of magnitude smaller in surface resistivity than the unlit portions, the measured resistance at the edges of the wafer will be determined by the resistance under the dark-spot. When the dark-spot is scanned over the entire wafer surface, measurement of the signal provides a topographical representation of the sheet-resistance of the wafer. Results were obtained on three 2-in.-diameter GaAs wafers grown by two different manufacturers. These results allow contours of isoresistive domains to be defined.The measurements confirm Jordan's theoretical model for the dislocation density distribution of LEC-pulled GaAs wafers, and thus give validity to the method. Because Jordan's thermodynamic model represents a theoretical lower limit for the dislocation distribution, the results obtained from the method developed here can give a measure of substrate quality and eventually determine guidelines in acceptance tests. This technique is capable of scanning large-area GaAs wafers at high speed and with good sensitivity. It may be, therefore, considered competitive with comparable X-ray evaluation methods when high resolution is not a requirement.
The interface between device and circuit design
Authors: Foss R. C. , Silburt A. L.
Published: April 2011

A proper understanding of transistor and other circuit-element behavior is critical in the design process of integrated circuits intended for high-volume production or exacting performance standards. Models of such elements are a key ingredient in the circuit-simulation task, which provides design-verification feedback to chip designers. Failures in this process can have costly consequences. Much of the effort put into modelling work contributes very little to real needs as practical failures are usually at the much more gross level of user input or program-coding problems.
A precision design technique for analog very large scale integration
Authors: Kumar K. R. Lakshmi , Hadaway R. A. , Copeland M. A. , King M. I. H.
Published: April 2011

A study of the matching characteristics of components available in a CMOS VLSI technology is reported. This examination has been extended to produce a design methodology for precision analog functions in VLSI by choosing a digital-to-analog converter as an example. The major emphasis of the paper will be on the device and technological aspects of the design approach.
Effect of electron bombardment during deposition of cadmium sulfide films using a hot-wall technique
Authors: Haque A. , Dixon A. E. , Brodie D. E.
Published: April 2011

The use of electron-beam irradiation combined with a hot-wall technique during deposition of CdS films is described. CdS films 2–10 μm thick were thermally deposited with and without electron bombardment on glass substrates using a hot-wall technique under a pressure greater than 1 × 10−6 Torr (1 Torr = 133.3 Pa). Film properties were studied using low-angle X-ray diffraction, scanning electron microscopy, optical microscopy using a chemical decoration technique, Hall-effect measurements, and temperature-dependent dark conductivity. The surface grain size varied from 2 to 5 μm and films were brownish orange with a smoky appearance.
Improved efficiency of CdZnS thin-film solar cells
Authors: Chandrasekhar S. , Martinuzzi S. , Nataren F. Z.
Published: April 2011

For low Zn concentrations i.e., x < 0.1, the performance of the Cd1−xZnxS–Cu2S solar cells can be improved by reducing the grain-boundary recombination. This has been achieved by growing well-oriented, homogeneous, ternary compound films.It was found that the Cd1−xZnxS films grown on the polycrystalline CdS films achieved the same larger grain size as that of the base layer. These films had fewer misorientations and had a unimodal grain-size distribution. There is a continuity in the crystallites from the CdS base to the Cd1−xZnxS overlayer, and the bifilms thus grown are less resistive than Cd1−xZnxS single layers.
Crystallization and dopant activation of amorphous silicon films by light annealing
Authors: Chen Z. M. , Wong S. K. , John P. K. , Prasad M. , Tong B. Y.
Published: April 2011

Amorphous-silicon (a-Si) thin films prepared by three different methods, namely, glow discharge, low-pressure chemical-vapour deposition (LPCVD), and electron-beam evaporation, were crystallized using an incoherent white-light source. The light source used was a plasma arc with a duration of ~10 μs with an incident light intensity of ~5 J/cm2. The crystal-growth mechanism in a thin film is briefly discussed. The films were characterized by measurements of electrical conductivity and its temperature dependence, optical microscopy, x-ray diffraction, and Raman spectroscopy. The dark conductivity of the a-Si films differed greatly depending on the method of preparation and ranged from 10−11 to 10−6 Ω−1∙cm−1. After crystallization by a single light flash, they all had approximately the same dark conductivity in the range 10−5–10−4 Ω−1∙cm−1. Crystallization of doped LPCVD films by the light source resulted in a six orders of magnitude increase in their electrical conductivity, clearly indicating dopant activation.
Noninjecting, high-barrier junctions on p-type silicon
Authors: Tarr N. Garry
Published: April 2011

The fabrication of junctions with very low minority-carrier injection ratios and reasonably good diode characteristics on p-type silicon is reported. These junctions were formed by growing an ultrathin oxide layer on a monocrystalline substrate, depositing polysilicon heavily doped in situ with phosphorus over the oxide, overlaying the polysilicon with aluminum, and then annealing the resulting sandwich structure at temperatures in the range 400–450 °C. The junctions can exhibit leakage current densities below 10−6 A∙cm−2 at moderate reverse bias and reverse breakdown voltages in excess of 20 V. The absence of minority-carrier injection has been demonstrated by diode reverse recovery transient measurements and by the fabrication of bipolar transistors employing these junctions as emitters.
On the potential interest of sub-0.25-μm metal-semiconductor field-effect transistors
Authors: El-Sayed Osman L. , El-Ghazaly S. , Salmer G.
Published: April 2011

The potential performance improvement achieved by reducing the gate length of GaAs MESFET's below 0.25 μm is investigated using a novel two-dimensional nonlocal numerical model. The charge, potential, and electron energy distributions in three devices having respectively 0.5-, 0.3-, and 0.15-μm gates are analyzed to provide an insight into the transport phenomena at hand. The I-V characteristics and the small-signal parameters are evaluated and the effect of gate length assessed. It is shown that no improvement in cutoff frequency is achieved below 0.2 μm while the effect of parasitic capacitance and gate-access resistance becomes more detrimental.
Auto-épitaxie et propriétés d'As–Ga obtenu par épitaxie en phase vapeur à partir de composés organo-métalliques
Authors: Benzaquen M. , Walsh D. , Auclair J.
Published: April 2011

Lightly compensated epitactic n-type GaAs is obtained by metal-organic vapour-phase epitaxy (MOVPE) with free-carrier concentration in the low 1015 cm−3 range and with good uniformity of both thickness and impurity concentrations over a 2-in.-diameter area (1 in. = 2.54 cm). Detailed Hall-effect and photoluminescence measurements are reported. At temperatures below 8 K, the conductivity is governed by variable-range hopping, clearly indicating a band of localized donor states. At higher impurity concentrations, a metallic contribution to the conductivity suggests a buildup of extended states near the middle of this band. These results are consistent with the observed photoluminescence.
Lumped-element components for GaAs monolithic microwave integrated circuits
Authors: Gaudreault M. , Stubbs M. G.
Published: April 2011

Gallium-arsenide monolithic microwave integrated circuits (GaAs MMIC's) promise the microwave circuit designer significant size, weight, and reliability advantages. Distributed and lumped matching techniques have been utilized previously in MMIC design with the latter offering greater bandwidth and smaller size. In this paper, experimental results for lumped interdigitated capacitors on a gallium-arsenide substrate are presented. Computer modelling in the frequency range 2–18 GHz was used to derive a set of design curves for these capacitors. These curves cover aspect ratios of w/s = 1 and w/s = 2.5. Experimental results obtained by using these curves to design lumped-element monolithic filters show excellent agreement with theory.
A mechanism for induced surface degradation of high-resistive GaAs during device fabrication
Authors: Rastogi A. C. , Teh C. K. , Weichman F. L.
Published: April 2011

Undoped, liquid-encapsulated-Czochralski (LEC)-grown, semi-insulating (SI) GaAs crystals were electrically characterized by temperature-dependent Hall effects and conductivity measurements to establish the mechanism for thermally induced surface degradation. X-ray photoelectron spectroscopy (XPS) was used to obtain depth profiles of the Ga and As composition, and the nature of the defect complexes and their changes were determined using Fourier-transform infrared spectroscopy (FTIR). Boron-related inhomogeneities were found to occur, and although it is normally considered a passive impurity, we conclude that it was in fact responsible for the detrimental p-conversion through the formation of BGa–Ga(i), BGa–GaAs, and BGa–VAs defect complexes. We propose that boron homogenization inhibits the escape of Ga from the crystal surface during annealing, leaving an excess of Ga in the p-converted layers. With FTIR we observed changes in the local vibrational-mode absorption of the acceptor defects SiAs, CAs, and the donors BGa, SiGa, and BGa–SiAs upon annealing. We present a theoretical analysis, which explains the observed changes in electrical characteristics on the basis of variations in deep-donor compensators, less deep donors, and net shallow acceptors, and conclude that higher device yields are achievable in SI GaAs if boron contamination can be reduced.