bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Responses of Poly(vinyl toluene) Plastic Scintillators at High Excitation Doses
Authors: Powell R. C. , Harrah L. A.
Published: February 2004

The light output intensities from commercial Pilot B and similar plastic scintillators having a poly(vinyl toluene) host were measured as a function of dose from a pulsed electron beam machine. At doses exceeding ∼ 1.5 × 104 rad in 3 × 10−9 sec, nonlinear responses were observed. For pure poly(vinyl toluene) the nonlinear responses can be explained by bimolecular interaction of the host excited states, and the product of the excited-state yield times the interaction rate constant is 8.5 × 10−10 cm3 sec−1 per 100 eV. For Pilot B it is concluded that the dominant quenching mechanism is the reabsorption of scintillator light by mononegative ions of th e center fluor, p-terphenyl. This conclusion is corroborated by the observation of the spectrum of decreased light transmission through the sample after electron excitation at high doses. The observed product of ion yield times extinction coefficient is 2.3 × 105 liter mole−1·cm−1 per 100 eV.
ESR Study of OH Radicals Originating from Water of Crystallization of Carboxylic Acids. I. Sodium Hydrogen Maleate Trihydrate
Authors: Toriyama Kazumi , Iwasaki Machio
Published: February 2004

The OH radicals originating from water of crystallization have been found in an irradiated single crystal of sodium hydrogen maleate trihydrate. This may be the first example of OH radical formation in hydrated organic crystals. We have found two types of OH radicals having different orientations and g tensors with nearly the same hyperfine tensors. The principal values of the g tensors were determined to be (2.0034, 2.0081, 2.0618) for OH(I), and (1.9947, 2.0065, 2.1198) for OH(II). The hyperfine tensors were found to be (− 27.0, − 44.7, + 3.5)G and (− 29.4, − 44.8, + 4.8)G, respectively, the relative sign being determined by the forbidden transitions. It was also found from the principal directions of the hyperfine and g tensors that the OH radicals are trapped in such a way that the O–H bonds in OH(I) and OH(II) are approximately parallel and perpendicular to the molecular plane of the hydrogen maleate ion, respectively, making an angle of 100°–105° with each other. The larger g anisotropy in OH(II) is considered to come from such a difference in the trapping site that the radicals interact with the surrounding molecules more weakly. The energy separations of the two oxygen Pπ orbitals were estimated to be 0.58 and 0.29 eV for OH(I) and OH(II), respectively.
Accurate Analytical Self-Consistent-Field Wavefunctions for Dy2+
Authors: Synek M. , Ramirez R.
Published: February 2004

Accurate analytical self-consistent-field (SCF) wavefunctions were calculated for the dysprosium laseractive ion, namely for Dy2+, (Z = 66), 4f10, 5I. These ab initio calculations were done by the analytical SCF expansion method, with full exchange effects for all the 64 electrons included. All of the basis function exponents in the analytical expansions were exhaustively optimized. These results represent the only analytical wavefunctions for Dy2+ available at this time. Our usual accuracy criteria were satisfied in these calculations.
Optical Spectra of Vanadium Ions in Yttrium Aluminum Garnet
Authors: Weber M. J. , Riseberg L. A.
Published: February 2004

Optical absorption and emission spectra of vanadium impurities in Y3Al5O12 crystals are reported. Crystals doped with vanadium only and with vanadium counterdoped with charge-compensating calcium and silicon ions were studied. Possible valence states for vanadium include V2+, V3+, V4+; possible substitutional sites in the garnet lattice include octahedral Al3+, tetrahedral Al3+, and dodecahedral Y3+. The observed spectra are interpreted as arising from octahedrally coordinated V3+ and V4+ and tetrahedrally coordinated V3+ and V4+. No spectral evidence of V2+ or of vanadium in dodecahedral sites was found. Vanadium-to-neodymium energy transfer was also investigated and is discussed.
Helix to Random Coil Transition in n-Stranded Molecules with Excluded Volume Effect
Authors: Kumbar Mahadevappa M.
Published: February 2004

The Lifson—Zimms' theory for helix to random coil transition has been extended to n-stranded polynucleotides. Formulas are derived which relate the stacking free energy and ring closure index to the maximum slope of the helix to coil transition in matching and dAT:dAT polynucleotides. The effect of inter- and intrastrand excluded volumes on transition point and on the stacking free energy in double stranded molecules has been examined. Both excluded volume effects have been expressed by a single parameter γ, which appears in the relation between the mean square end-to-end distance and the number of units in a given polymer. It is concluded that the interstrand excluded volume effect shifts the transition point, descreases the τ value, and increases the ε value for double-stranded molecules.
Microwave Absorption and Molecular Structure in Liquids. LXXVIII. Dielectric and Association Behavior of Six Isomeric Octyl Alcohols in n-Heptane Solution
Authors: Crossley J. , Glasser L. , Smyth C. P.
Published: February 2004

The dielectric constants and losses of six isomeric octyl alcohols at concentrations of 0.03–0.35 mole fraction in n-heptane solution at 25°C have been measured at wavelengths of 0.204, 1.23, 3.23, 9.99, 24.8, and 49.9 cm, and the so-called static dielectric constants have been measured at 575 m. For three of these alcohols at mole fraction 0.32–0.33, dielectric constant and loss measurements were also made with an RX meter at seven wavelengths from 120 to 600 cm. A new analysis of this measuring system has been carried out to obtain more accurate values of dielectric constant and loss. For those isomers in which the methyl group is attached to the same carbon atom as the hydroxyl group or to the adjacent carbon, the dielectric absorption may be characterized by two relaxation times at all the concentrations employed. The isomers containing a relatively less-shielded hydroxyl group exhibit an additional low-frequency relaxation time at the higher alcohol concentrations. In all cases, the magnitude of the shortest relaxation time, which dominates the absorption of the most dilute solutions, is only slightly concentration-dependent and is characteristic of the relaxation of an hydroxyl group about its C–O bond. The intermediate relaxation process lengthens and makes a relatively greater contribution to the dielectric absorption with increasing alcohol concentration. The low-frequency process would appear to be associated with the existence of one or more higher polymers at the higher concentrations.
Ultrasonic and Relaxational Spectroscopy of Fast Reactions. I. Gas
Authors: Tabuchi Daisaku
Published: February 2004

As a method of ultrasonic spectroscopy in gas, ultrasonic absorption and dispersion in gas due to multiple reactions are treated theoretically and the interaction of the relaxations is examined. The complex velocity of sound is calculated from the changes of the number of moles, the pressure, the volume, the internal energy, and the rates of the reactions by sound wave. The heat capacities for gases at constant pressure and at constant volume are composed of the terms of a simple mixture, the terms due to each reaction, and the terms due to the mutual interaction of the reactions. The latter two terms depend on the sound frequency, and the last terms are pointed out for the first time. Examples involving one and two reactions are shown, and Einstein's equations are derived as a special case of one reaction. The characteristics of the ultrasonic spectrum and a numerical example will be treated in a later paper.
Entropy and Molecular Correlation Functions in Open Systems. II Two- and Three-Body Correlations
Authors: Mountain Raymond D. , Raveché Harold J.
Published: February 2004

We consider the contributions from the correlation of pairs and triples of molecules to the configurational entropy per molecule of a simple fluid system. Using numerical values of the pair function and only certain moments of the triplet function, we have computed the first few terms in an expression for the entropy in terms of the correlation functions. The results, which compare favorably with experimental values over a range of densities including that of the liquid, indicate that contributions from the correlations of triples of molecules can be appreciable. The computations are done for a fluid of hard spheres and liquid neon and the results are discussed in terms of the molecular correlations in a simple fluid.
Configuration-Interaction Calculations for Small Pi Systems. IV. Spin and Charge Densities of Various Heteromolecules
Authors: Burrows B. L.
Published: February 2004

The spin and charge densities of a number of substituted benzene heteromolecules are calculated by full configuration interaction. The results are compared with those calculated by Hückel theory and are found to be qualitatively in agreement. The significance of the near degeneracy of the Hückel molecular orbitals is discussed. Two types of substituted benzenes are considered, the electropositive aza substitution and the electronegative methyl substitution. Particular consideration is given to the positive and negative ions.
EPR Pulse Radiolysis Studies of the Hydrogen Atom in Aqueous Solution. I. Reactivity of the Hydrogen Atom
Authors: Smaller B. , Avery E. C. , Remko J. R.
Published: February 2004

The transient properties of hydrogen and deuterium atoms produced by pulse radiolysis in water have been studied by EPR. Details of the EPR instrumentation are described. From decay characteristics of the EPR signal on addition of various solutes, rate constants for the reaction of atomic hydrogen with various classes of molecules have been determined. Agreement of our results with prior indirect determinations is, in general, good. The isotope effect is also in agreement with expectation.
Proton Spin Relaxation Study of the Cholesteric-to-Nematic Phase Transition
Authors: Dong Ronald Y. , Pintar M. M. , Forbes W. F.
Published: February 2004

The magnetic field in which a NMR experiment is performed can serve as the critical field for the cholesteric-to-nematic phase transition. The proton spin—lattice relaxation times, T1 and T1ρ, were measured in two cholesteric mixtures (p-azoxyanisole containing small amounts of cholesteryl chloride) to study the orientational order fluctuations in the cholesteric phase and at the thermally-induced cholesteric-to-nematic phase transition.
NMR of KBiF6 Powder: The Sign of Bi–F Spin—Spin Coupling and the Bi Quadrupole Coupling
Authors: Fukushima Ehchi
Published: February 2004

An analysis of 19F NMR spectra of polycrystalline KBiF6 is performed by matching computer generated spectra with the observed spectra. The complex patterns of the spectra arise from a scalar spin—spin coupling between the spin-9/2 209Bi which interacts with the electric field gradient via the quadrupole interaction and the spin-1/2 19F. The fits of the experimental spectra with the calculated spectra are good and yield the following parameters. The Bi—F spin—spin coupling is ∓ 2.7±0.3 kHz and the 209Bi quadrupole coupling e2qQ/h in KBiF6 is ±132±12 MHz with the top signs favored from crystallographic and NMR considerations.
Electron Paramagnetic Resonance Absorption in Oriented Phosphorescent Triphenylene-h12 and Triphenylene-d12 from 4 to 250°K
Authors: Gerkin Roger E. , Szerenyi Peter
Published: February 2004

Electron paramagnetic resonance absorption by phosphorescent triphenylene-h12 and -d12 oriented in single crystals of symmetric dodecahydrotriphenylene has been investigated in the temperature range from 4 to 250°K. It has been shown that both guest molecules are multiply oriented in this host. In addition, two distinct kinds of mixed crystals have been identified on the basis of the zero-field splittings manifested by the guest molecules. In one kind of mixed crystal, guest splittings were found to change with time until stable, fixed values were established. Since splitting differences are related to orientational differences, guest rearrangement in the solid host is implied, which has not heretofore been reported. The temperature dependence of at least one zero-field splitting parameter D is complex in that its magnitude does not increase monotonically with decreasing temperature. The temperature dependences of the zero-field splitting parameters E are even more complex. X-ray diffraction data indicate that both kinds of mixed crystals have the same over-all host structure and are free from disorder. The unit cell deviates slightly from the previously reported hexagonal type, indicating lower than threefold site symmetry. Because of this, and also because of the multiple orientation, the E parameters of the triplet guests cannot be expected to vanish. The data provide some evidence that the entire magnitude of E is due to the molecular-crystal field. The decays of the resonance absorptions of both guests were investigated as functions of temperature, and the angular dependence of the resonance absorption linewidths for triphenylene-d12 has been studied near 77°K. The wavefunction of the lowest triplet state of trigonal triphenylene, and its energy relative to the ground state, have been calculated in the Pariser—Parr—Pople approximation. The zero-field splitting parameter D has been calculated using two-center integrals evaluated by the Gaussian-transform method. The calculated values of both the energy and D are in very good agreement with experimental values.
Paramagnetic Relaxation Study of Spatial Distribution of Trapped Electrons in Gamma-Irradiated Organic Glasses
Authors: Lin D. P. , Kevan Larry
Published: February 2004

Paramagnetic relaxation characteristics of trapped electrons in γ-irradiated glassy 3-methylpentane (3-MP) at 71°K, and triethylamine (TEA) and methyltetrahydrofuran (MTHF) at 77°K were studied by power saturation techniques. For MTHF and TEA the characteristic relaxation time, (T1T2)1/2, is constant with radiation dose at low doses and decreases at higher doses. For 3-MP the relaxation time decreases even at low dose. Together with data on the total spin concentration the results are interpreted in terms of a ``spur'' model in which the radiation-produced trapped electrons and radicals are trapped in clusters at low dose and constitute a nonuniform spatial distribution. According to this model the spur radius is 〉130 Å in 3 MP, 101 Å in TEA, and 63 Å in MTHF. These radii compare with 58 Å for trapped electrons in glassy methanol and 41 Å in glassy alkaline ice (10M NAOH). For all of these matrices the radius within which the electrons are trapped appears to increase with decreasing polarity of the matrix, and consequently radiation-produced electrons appear to travel farther before being trapped in less polar matrices.
Ionization of Long-Lived Highly Excited Atoms by Collision with Molecules
Authors: Matsuzawa Michio
Published: February 2004

For the ionization of long-lived highly excited atom A** by collision with molecule B A**+B→A++B+e, a mechanism is proposed in which an electron in the long-lived highly excited atom is ionized as a result of its energy gain from the molecule by the rotational de-excitation. The cross sections at thermal velocities are calculated to be of the order of 10−13 cm2 for polar molecules according to the proposed mechanism. This result is in reasonable agreement with experimental data.
Models for the Order—Disorder Transition in NaH3(SeO3)2
Authors: Nagle J. F. , Allen G. R.
Published: February 2004

The entropy of the Makita—Miki model for NaH3(SeO3)2 is shown to be exactly solvable by transformation into a Slater KDP model problem. However, arguments are presented to show that the model is unsatisfactory. Two additional models are introduced. The first model is reduced to a dimer problem and is solved exactly. The solution is interesting in the context of critical phenomena, but it indicates that the model is not a good one for NaH3(SeO3)2. The second model is readily solved in the limit of high temperature using results for the two-dimensional Ising model. Although this model is too difficult to solve exactly at finite temperature except for one limiting case, it is encouraging that analogous models exhibit multiple phase transitions.
On a Vibrational Analysis of S2Br2 and S2Cl2
Authors: Frenzel C. A. , Blick K. E.
Published: February 2004

Recent investigations of the Raman and infrared spectra of S2Br2 and S2Cl2 have reported new polarization data and the observation of previously unreported fundamentals. A normal coordinate analysis investigates the transferability of the valence force field for these molecules, and the results of these calculations are reported in terms of potential-energy distributions, vibrational mean amplitudes, Cartesian atom displacements, and Coriolis coupling coefficients. The respective spectra are discussed in light of these data, and a value for the S—S force constant is reported.
Doppler Broadening in Beam Experiments
Authors: Chantry P. J.
Published: February 2004

The distribution in center-of-mass energy caused by the thermal motion of the target gas molecules has been rigorously derived for the case of a monoenergetic particle beam interacting with target molecules having an isotropic Maxwellian velocity distribution corresponding to temperature T°K. Provided the nominal c.m. energy E0 exceeds a few kT, the distribution has a full width at half-maximum (FWHM) of W1/2=(11.1γk T E0)1/2. where γ=m/(m+M), m and M being the projectile and target masses. This is identical to the width derived previously in a one-dimensional approximate treatment by Bethe and Placzek. The exact and approximate distributions differ significantly, however, in shape and mean energy, particularly at low values of E0/γkT. The Doppler width, W1/2, is shown to significantly affect the appearance curve of the products of endothermic reactions involving heavy particles. Convolution integrals are derived for a number of idealized forms of the cross section for such reactions. In the extreme case of a step-function cross section the estimation of the threshold ET by the usual linear extrapolation technique gives a value which is too low by approximately 0.6W1/2 (ET), where W1/2 (ET) is the FWHM evaluated at E0=ET. The effect of the thermal velocities of the parent molecules from which the primary beam is formed is considered in the case of an accelerated beam with no kinetic energy imparted to the beam particles by the formation process, and in the case where the energy of the interacting particles is controlled only by the kinetic energy released in a resonant dissociative formation process. The latter situation is shown to be described exactly by the equations derived for the monoenergetic beam case provided an appropriately defined equivalent temperature is used in place of the true temperature of the target gas. The results of the present theory are applied to the experimental data of Berkowitz, Chupka, and Gutman on the reactions I−+O2→O2 −+I and I−+NO→NO−+I. In addition data on the reaction O−+O2→O2 −+O are presented and analyzed. The derived thresholds are consistent with A (O2)≥0.56±0.10 eV, A (NO)≥0.06±0.1 eV, and A (O2)≥0.50±0.1 eV, respectively. The experimental data of Maier on the reaction C++D2→CD++D is found to be consistent with a cross section which rises from threshold with approximately twice the slope of the cross section computed by Truhlar from statistical phase space theory.
Stochastic Models for the Statistical Description of Lattice Systems
Authors: Alexandrowicz Z.
Published: February 2004

Macroscopic properties of lattice systems are described by stochastic models that permit one to construct ``typical'' configurations representing the average behavior. The transition probabilities for the models are defined with parameters expressing both short- and long-range correlations; the parameters are varied to maximize a ``pseudo'' partition function and the relative worth of models can be judged in terms of these maxima. The actual construction of the lattice configurations is carried out by Monte Carlo and, since only one typical configuration is needed, quite large lattices (w≃105) can be easily described. For the simpler models the construction can be formulated analytically, in view of continuity conditions. The method was applied to the Ising problem in 2 and 3 dimensions, yielding quite accurate results with a phase transition not far off from the exact (Kc ′= 0.428 vs 0.4407) and in close agreement with series expansion (Kc ′= 0.223 vs 0.2217), for the two cases respectively. The important point is that—in contrast to other methods—the use of stochastic models can be readily extended to more involved problems, like to the presence of external field, further neighbor interactions, or admissibility of several states for a site.
Studies of Vibration Spectra of Bonded Hydrogen Atoms Using a Pulsed Neutron Source
Authors: Day D. H. , Sinclair R. N.
Published: February 2004

The vibration spectra of some hydrogeneous compounds have been studied over the range 300–4000 cm−1 by observing incoherent neutron scattering. The paper describes the use of a crystal analyzer technique with a pulsed neutron source based on the Harwell 45-MeV electron linac. Time-of-flight spectra of neutrons downscattered to a final energy, fixed by the crystal spectrometer, were measured. Data for ZrH2, H2O, NaNH2, and C6H5NH2 are reported and compared with available results from optical spectroscopy and, in the first two cases, other neutron scattering data.
Interaction of Gas Atom with a Hot Solid Surface: A Harmonic Model Analysis
Authors: Forman R. E.
Published: February 2004

The interaction of a monoenergetic gas beam with a hot surface is viewed as a collection of discrete two-body collisions. By use of a soft-cube model with a truncated harmonic interaction potential, the interaction is reduced to a linear problem. The solution to this simplified view indicates that an important role of thermal motion of the solid atoms is reflected in the distribution of their initial conditions at the time interaction begins. Specifically, the initial condition distribution is biased toward interactions beginning with greater than average relative velocity between gas and solid atoms. The average exit velocity of the gas is expressed as an integral over the initial condition distributions. This integral cannot be evaluated exactly in closed form and an approximate analytical evaluation is obtained. A computer simulation of the problem was devised and shows satisfactory agreement with the theoretical value for the average relative velocity at the start of interaction and the analytical approximation for the average gas exit velocity.
Catalysis on Wide-Band-Gap Semiconductors
Authors: Lee V. J.
Published: February 2004

This paper presents two novel models of catalysis on wide-band-gap semiconductors: injection of electrons (holes) into the conduction (valence) band by donor (acceptor) intermediates and extraction of electrons (holes) by acceptor intermediates in concurrence, while the catalytic surface reaction via ionic intermediates is in progress. At the stationary state of catalysis, the two concurrent rates of charge transfer are assumed exactly equal in magnitude so that conservation of charges are maintained. The models of catalysis provide an interpretation of the variation in catalytic activity with the surface potential of an extrinsic semiconductor induced by an external electrostatic field, and of the variation in apparent activation energy with the bulk potential. Moreover, this theory sheds light on the complexity and the significance of catalytic experiments carried out under dynamic conditions.
Thermal Dissociation Rate of CsF
Authors: Mandl A.
Published: February 2004

The thermal dissociation rate constant (kd) of CsF has been measured in the temperature range 3500°K ≤ T ≤ 5000° K. CsF dissociates almost entirely into the ionic branch CsF+M ⇄ lim kτk dCs++F−+M. Using our measured dissociation rates we have calculated ion—ion recombination rates (kr) and compared our results with the theory of Bates and Flannery for ion—ion recombination. The agreement is good within our experimental uncertainties.
Electronic Excitation in Fast Collisions of Na with SO2 and NO2
Authors: LeBreton P. R. , Mecklenbrauck W. , Schultz A. , Schlier Ch.
Published: February 2004

A sputtered Na beam has been used to investigate collisionally induced electronic excitation in scattering with SO2 and NO2. Light from the radiative decay of excited electronic states was observed at several wavelengths, and measurements were made of the excitation cross sections as a function of the center-of-mass collision energy in the range 1–30 eV. In both scattering systems, the most intense light measured originated from the Na (32P→32S) D line. Light from the (42D→32P) Na transition was observed, but its intensity was more than an order of magnitude smaller than that of the D line. Emission also occurred from transitions with long radiative lifetimes (∼40 μsec). This emission is probably due to the B1→A1 molecular transitions of SO2 and NO2. The results have been discussed in terms of a potential curve-crossing mechanism which seems to satisfactorily explain collisionally induced alkali atom excitation. For the molecular emission, an alternate mechanism has also been considered which involves vibrational coupling of the A1 and B1 states.
Excimer Fluorescence of Poly(N-vinylcarbazole)
Authors: Johnson P. C. , Offen H. W.
Published: February 2004

Fluorescence spectra and lifetimes of carbazole, 1,3-bis(N-carbazolyl)propane and poly(N-vinyl-carbazole) have been studied as a function of pressure to 30 kbar at room temperature and 77°K. Polymer films show exclusively excimer fluorescence (τ=43 nsec) at room temperature. This is not quenched at 77°K but appears together with a new emission (τ=12 nsec) attributed to traps arising from exciton coupling between adjacent carbazole chromophores. The comparative P, T response of the three compounds suggests that excimers do not form between adjacent chromophores in the amorphous polymer.
Scattering of Helium Atoms by Phonons in the (001) Surface of LiF at 150°K
Authors: Williams Brian R.
Published: February 2004

Results are presented for the scattering of a beam of helium atoms (obtained from a nozzle source) from a cleaved lithium fluoride surface maintained at 150°K. The scattering patterns reveal two types of scattering events: (1) coherent scattering, showing a large number of diffraction peaks not reported to date, and (2) inelastic scattering resulting from the vibrations of surface atoms. This component of scattering is observed in the neighborhood of the elastic peaks, in the form of streaks, extending in particular directions outward from the Bragg angle. The shapes of the scattering patterns obtained follow the general predictions made for bounds imposed on the scattering surface by the incident velocity of the helium atom.
Transport Properties of a Gas of Diatomic Molecules. III. RDW Approximation to the Rotational Relaxation Time
Authors: Olmsted Richard D. , Curtiss C. F.
Published: February 2004

A quantum mechanical expression for the relaxation time is obtained for a low density gas of rotating diatomic molecules. The development is based on the restricted distorted wave approximation to rotationally inelastic scattering. The particular case of a gas of rigid spheres with embedded point dipoles is discussed. The classical limit of this result is also determined and agrees with the result obtained by another method.
Excited State Chemistry of the Ferrocyanide Ion in Aqueous Solution. I. Formation of the Hydrated Electron
Authors: Shirom Miriam , Stein Gabriel
Published: February 2004

Excitation of the Fe(CN)64− ion in aqueous solution into the 1T1u or 1T2g excited singlet state, below 313 nm, leads to hydrated electron formation in competition with internal conversion to the lowest excited singlet 1T1g state. The limiting quantum yield of hydrated electron formation is a linear function of quantum energy between 313 and 228 nm, reaching φe≃ 0.9 at 228 and 214 nm. Above 313 nm hydrated electron formation is not observed, but photoaquation is. Dependence of Φe on scavenger (N2O) concentration is observed. The involvement of CTTS character in the process, and the role of rapid solvent rearrangement in the dissociation of the excited state, are discussed.
Electron-Acceptor—Electron-Donor Interactions. XVII. Concerning the Electron Affinities of Sulfur Hexafluoride and Some Other Electron Scavenging Molecules
Authors: Hammond P. R.
Published: February 2004

Additional absorptions found when sulfur hexafluoride and other electron scavenging species are dissolved in tetrakis (dimethylamino) ethylene (TMAE) are ascribed to charge-transfer bands, and the order of the absorption onsets is related to the order of electron affinities. Sulfur hexafluoride is a weak acceptor, which by comparison with previous measurements appears to have a small positive value for Eav of about 0.60 eV. Some fluorocarbons, oxygen, and naphthalene are compared. Just as the perfluorocycloalkanes are more effective electron scavengers than the linear, they produce yellow solutions in TMAE, whereas the linear do not. All interactions are extremely weak. A marked enhancement of the absorption of TMAE in hexafluorobenzene as compared with hexafluorobenzene in TMAE is ascribed to a geometrical limit imposed on site saturation.
Ionization—Excitation Processes in Zinc, Cadmium, and Mercury
Authors: Hyman Howard A.
Published: February 2004

Cross sections for ionization—excitation by photon and high-energy electron impact have been calculated for several states of zinc, cadmium, and mercury. Such processes are of interest both theoretically, in that they are an extremely sensitive probe into electron correlation effects in atoms, as well as practically, in that they may play an important role in the population of many upper ion laser levels. A model for the ionization—excitation process has been developed which takes full account of correlation in the initial state but includes only the screening part of the final-state interaction.
Aquoluminescence from γ-Irradiated Alkali Halides. II. Spectral Analysis and Effect of pH of the Medium
Authors: Arnikar H. J. , Damle P. S. , Chaure B. D.
Published: February 2004

The emission of a bluish-green glow during the dissolution of γ-irradiated alkali halides has been recently reported under the name of aquoluminescence. We present here details for its production, observation, and for the measurement of its intensity. Typical oscillograms of the glow and its spectral analysis are also given. A probable mechanism for the origin of aquoluminescence is suggested consistent with the effects observed thereon due to pH of the medium and the addition of electron acceptors and donors prior to dissolution of the irradiated salt.
Removal of Orbital Degeneracy in the Mesitylene Dimer Radical Cation
Authors: Shih S. , Dessau R. M.
Published: February 2004

The cobaltic trifluoroacetate oxidation of mesitylene in a rapid mixing flow system resulted in the formation of the mesitylene dimer radical cation. The hyperfine splitting constants obtained from the ESR spectrum indicated the removal of orbital degeneracy in the dimer radical cation by a cooperative intermolecular vibronic effect.
Analytical Evaluation of Multicenter Molecular Integrals. II. Three- and Four-Center Coulombic Integrals over Hydrogenic Orbitals of Integral Principal Quantum Number
Authors: Alper Joseph S.
Published: February 2004

The three- and four-center Coulombic integrals over hydrogenic orbitals characterized by integral principal quantum numbers are evaluated analytically. The projected momentum space method in which the properties of the four-dimensional spherical harmonics play a crucial role is used in the derivations. The resulting formulas are devoid of infinite summations. However, the appearance of generalized hypergeometric functions prevents the expression of the molecular integrals in closed form.
Analysis of the Barker—Henderson Local-Compressibility Approximation
Authors: Moffat Marshall J. , Kozak John J.
Published: February 2004

In this paper, the Barker—Henderson theory is analyzed. Resummation procedures are introduced so that the local-compressibility approximation can be studied within the framework of a density expansion. Using this representation, it is possible to characterize the Barker—Henderson closure using diagrams, and it is found that the set of diagrams which are summed using the local-compressibility approximation comprise a rather small subset of the total number of diagrams which are generated by the exact theory. Numerical calculations are performed in order to estimate the contribution of diagrams which are neglected in the Barker—Henderson theory. Based on this analysis, a possible reason is given to explain the success of the theory.
Spectrum of Light Scattered from Charged Macromolecules in Solution
Authors: Stephen Michael J.
Published: February 2004

Many macromolecules of biological interest, when dissolved in water, acquire charges and these charges are shielded by an atmosphere of counterions. The effect of the ion atmosphere on the diffusion constants of the molecules and hence on the spectrum of scattered light from such a solution is investigated here using a simple model. It is found that the ionic atmosphere can have an important effect on the diffusion of the macromolecules and that measurement of the spectrum of scattered light may provide a way to measure the residual charge on the macromolecules.
Measurements of Rate Constants for Termolecular Reactions of O(3P) with NO, O2, CO, N2, and CO2 Using a Pulsed Vacuum-uv Photolysis—Chemiluminescent Method
Authors: Stuhl F. , Niki H.
Published: February 2004

Absolute rate constants for a number of termolecular reactions of O atoms were determined at 300°K. Oxygen atoms were generated by pulsed vacuum-uv photolyses of NO, O2, CO2, and N2O and were monitored by NO2* or CO2* chemiluminescent emission. The rate constants k, in units of cm6 molecule−2·second−1, for the following reactions are: O+NO+NO→NO2+NO,   k=1.5×10−31 (± 10 %) O+NO+He→NO2+He,   k=6.65×10−32 (± 10%) O+O2+O2→O3+O2,   k=6.4×10−34 (± 25 %) O+O2+N2→O3+N2,   k=5.4×10−34 (± 25 %) O+O2+CO→O3+CO,   k=6.7×10−34 (± 25 %) O+CO+CO→CO2+CO,   k=3.2×10−36 (± 25 %) O+CO+N2→CO2+N2,   k=2.2×10−36 (± 25 %) O+CO+He→CO2+He,   k=1.7×10−36 (± 25 %) O+CO2+CO→CO3+CO,   k〈9×10−36 O+N2+N2→N2O+N2,   k〈5×10−38.
Exciton Theory of the Electronic States of Dye—Polymer Complexes. III. Configurationally Induced Optical Rotatory Dispersion of Dye Transitions in Helical Complexes
Authors: Philpott Michael R.
Published: February 2004

The exciton theory of dye—polymer complexes is applied to the phenomenon of optical rotation displayed by the electronic transitions of dyes bound to helical polymers. In the model examined one chromophoric ligand is bound to an infinite single stranded helical polymer. There are no symmetry restrictions on the ligand which can be optically active, e.g., an asymmetric dimer of dyes, or inactive as is the case with most dye molecules. Optical rotation arising from the coupling of electric transition dipoles and quadrupoles and magnetic dipoles of ligand and monomer units is considered. The transition moments of the ligand are resolved into three components each of which couples to particular members of the set of allowed helix transitions. Thus the helix moments enhance those of the ligand enabling it to rotate the plane of polarization of incident light if it is symmetric and changing the rotation if it is asymmetric. Expressions are developed for the optical rotation of linearly polarized light by complexes with random and certain fixed orientations.
Thermal Study of Three In—Tl Alloys in the Neighborhood of the fct—fcc Transformation; Heat Capacities from 5–300°K
Authors: Schwartz Robert G. , Gerstein B. C.
Published: February 2004

The heat capacities of three In—Tl alloys, having compositions of 34.6-, 28.9-, and 18.8-at.% Tl, have been measured from 5–300°K. The thermodynamic functions have been tabulated. In this temperature range, the 28.9-at.% Tl alloy exhibited a martensitic transformation from fct to fcc. The 34.6-at.% Tl alloy remained fcc and the 18.8-at.% Tl alloy remained fct. The entropies at 298°K were found to be 61.6±1.6, 61.4±2.0, and 61.1±1.6 J ( gaw·deg)−1 for the three alloys, respectively. The alloy that transformed from fct to fcc exhibited deviations from smooth behavior in the heat capacity in the region of the transformation. While no alloy exhibited anomalous behavior below 195°K, all alloys exhibited anomalous 5%–8% rises in heat capacity above 195°K. This behavior was exhibited over a 25° to 35° range, depending on the alloy composition. This rise in heat capacity was irreversible in the 28.9- and 34.6-at.% Tl alloys, but reversible, to within experimental error, in the 18.8-at.% Tl alloy. The behavior correlated with anomalous thermal expansion coefficients of fcc and fct alloys reported by previous investigators.
Thermodynamic Properties of Strontium Ammoniate and the Gaseous Formation Energy of Sr (NH3)62+
Authors: Plummer Gary , Senozan N. M.
Published: February 2004

The equilibrium pressure of ammonia over strontium ammoniate, Sr(NH3)6, has been measured at 18 temperatures extending from − 18 to 7°C. The standard enthalpy, free energy (at 0°C), and entropy of dissociation, Sr(NH3)6 (s)=Sr (s)+6NH3(g), per mole of ammonia have been determined to be 9.74±0.15 kcal, 1.68±0.02 kcal, and 29.5±0.6 eu, respectively. Combining the enthalpy of dissociation with other thermodynamic quantities, the gaseous formation energy of the strontium hexammine complex, Sr2+(g)+6NH3 (g)→Sr(NH3)62+(g), is found to be −256 kcal/mole. This value is qualitatively consistent with the electrostatic theory of coordination complexes in which the ligand molecules are assumed to have progressively greater induced dipoles as the central ion diminishes in size.
Comment on ``Absolute Differential Cross Sections of Elastically Scattered Electrons. II A Polarization Scattering Potential for Hg at 500, 400, and 300 eV''
Authors: Bonham R. A. , Fink M.
Published: February 2004

The interpretation of Bromberg's measurements of absolute experimental elastic scattering cross sections for Hg with 300, 400, and 500 eV incident electrons is discussed. Both multichannel Born series and a partial wave analysis utilizing a static polarization potential are employed to discuss the results. The desirability of comparing the accurate partial wave differential cross section for the static potential with the absolute experimental cross section is pointed out. In addition it is suggested that the observed exponential behavior of the experimental cross section is the result of multiple scattering of the incident electron wave.
Determination of Surface Tensions of Liquids from Liquid Meniscus Rise on Partially Immersed Plates
Authors: Morcos Ikram
Published: February 2004

Surface tensions of liquids can be determined from measurement of liquid meniscus height at an infinitely wide vertical plate. For a liquid which wets the plate with a zero contact angle the surface tension σ is given by σ=(ρ g/2)h2, where h is the meniscus height, ρ its density, and g the gravitational constant. Measurements were carried out with H2O, DMF, DMS, and CCl4 on a clean smooth glass plate. The results show that the error in surface tension is generally within the range of the experimental error of the method.
Phosphorescence and Fluorescence of Phthalocyanines
Authors: Vincett P. S. , Voigt E. M. , Rieckhoff K. E.
Published: February 2004

For the first time, phosphorescence has been observed from and clearly assigned to the molecular triplet of several metallophthalocyanine (Pc) molecules. The Pc's of Pt, Pd, Cu, Zn, and Cd have O–O bands in solution (77°K) at the extraordinarily low energies of 10 590, 10 100, 9390, 9150, and 9120 cm−1, respectively, while those of Mg and VO have possible transitions at ∼9000 and 8500–8800 cm−1. Half-widths, lifetimes, approximate quantum efficiencies, triplet absorption, and excitation spectra, and vibrational substructure are reported, together with oxygenation and heavy atom effects. The lifetimes were very short (varying from 1 msec to less than 3 μsec), so room temperature phosphorescence was seen, as was radiation from the separate triplet sublevels at 4°K and below. Yields were very low (∼10−2 to ∼10−5) because of very strong radiationless transitions, and various other Pc complexes did not seem to phosphoresce at all. Both tripdoublet and quartet luminescence were seen from CuPc, and the intersystem crossing time was estimated to be ∼1 nsec. Fluorescence is reported from several of the complexes, including PdPc.
Unit Compressibility Slopes and a New Virial Coefficient Interrelation
Authors: Holleran Eugene M. , Sinka Joseph V.
Published: February 2004

The slopes of isochors and isotherms as they cross the unit compressibility line are found to constitute a corresponding property for many fluids over a wide range of densities extending from dilute gases to compressed liquids. This correspondence is represented by a simple function, and its consequences for equations of state are examined. In particular, a new interrelation among the virial coefficients is derived. The interrelation is tested for the Lennard-Jones 12,6 intermolecular potential, and the agreement permits an estimation of this potential's previously unknown sixth virial coefficient as a function of temperature.
Characterization of Hot Hydrogen-Atom Reactions by Kinetic Spectrography
Authors: Tomalesky R. E. , Sturm J. E.
Published: February 2004

The flash photolysis of hydrogen iodide in the presence of nitrous oxide, carbon dioxide, and water has been investigated by kinetic spectroscopy. Although the fraction of hydrogen iodide dissociated was very large (∼25%), the only observable intermediate was imidogen which was shown to be from the hot-atom reaction H*+N2O→NH+NO. It was demonstrated that the rapid removal of imidogen and the apparent absence of hydroxyl radicals in each case is a result of Reactions (10) and (12), respectively, NH+HI→NH2+I, OH+HI→H2O+I. A lower limit of 3.5×108 liter/mole·sec was placed on the specific rate of (10) at room temperature.
Calculations of V–V Transfer Probabilities in CO–CO Collisions
Authors: Jeffers W. Q. , Kelley J. Daniel
Published: February 2004

This paper presents detailed calculations of vibration—vibration transfer probabilities in CO–CO collisions including both long-range and short-range interactions. Comparison is made with experimental data, and the results show that the relative contributions of the long- and short-range interactions to the V–V transfer probability depend on energy defect and temperature. Our calculations match the experimental data at 300°K to within 25%; at this temperature the the short-range interactions dominate in determining the transition probability for vibrational energy defects greater than 210 cm−1, while the long-range interactions dominate for smaller defects.
Quenching the Nuclear Overhauser Effect in NMR Spectra of Carbon-13
Authors: Freeman Ray , Pachler K. G. R. , Mar Gerd N. La
Published: February 2004

Fourier transform techniques have been employed to determine the spin-lattice relaxation time and the enhancement of the intensity of the carbon-13 signal of formic acid upon strong proton irradiation—the nuclear Overhauser effect. Addition of paramagnetic hexaquochromic perchlorate is found to decrease the relaxation time and the enhancement factor in the same proportion. Beyond a concentration of about 0.1M, the Overhauser enhancement is effectively quenched, line broadening is only just becoming apparent, and the loss of intensity can be fully recovered by readjustment of the pulse conditions to take advantage of the faster relaxation. The carbon-13 spin-lattice relaxation in neat formic acid is shown to proceed predominantly through dipolar interaction with the protons, and when paramagnetic ions are added they are found to act directly on the carbon nuclei rather than via the proton spins, a negligible ``three-spin effect.'' The quenching technique has been employed to establish uniform intensities for the four carbon-13 resonances of vinyl acetate, where normally there is a wide disparity in signal strength due to unequal Overhauser effects.
Integral-Transform-Generated Basis Sets
Authors: Yue C. P. , Somorjai R. L.
Published: February 2004

Two alternative versions of a procedure for generating new basis sets via the integral-transform (IT) method are outlined. The first version (fixed shape function, set of primitive functions) is tested on 3-electron (Z=2, 3, 4, 5) and 4-electron (Z=3, 4, 5, 6) atomic systems (ground state) and the 21P excited state of He. The set of primitive functions are either hydrogenic or Slater orbitals and the shape function is the square pulse that generates the Hulthèn transforms. In these calculations, a conjecture about the dependence of the parameters of higher principal quantum number (n) IT orbitals on the parameters of lower n IT orbitals is also tested and substantiated. The second version (single primitive function, set of shape functions) is tested on the 21P state of He. The primitive function is a 1s Gaussian function, the set of shape functions is related to the set of generalized Laguerre polynomials Lnv-1(x). The first member of this set gives kv(qr), the reduced modified Bessel function of the second kind, already used in ground state atomic and molecular calculations. The results are analyzed critically.
Search for the H32+ Ion
Authors: Berkowitz E. H. , Stocker H.
Published: February 2004

Charge stripping of H3+ and D3+ at 3–4 MeV was used to search for H32+ and D32+. Analyses by several means, including a search for nuclear reactions induced by the constituent nuclei, give no evidence for a stable doubly charged triatomic hydrogen molecule.
EPR spectra of Zn2GeO4:Mn
Authors: Feldman D. W.
Published: February 2004

We have observed the EPR spectra of divalent manganese in zinc germanate single crystals and solid state reacted powders. Two distinct spectra are seen which are interpreted in terms of Mn2+ substituting for Zn2+ in its two inequivalent sites. For one of the sites D=742×10−4cm−1 and E=192×10−4cm−1, and for the other site D=481×10−4cm−1 and E=156×10−4cm−1.
On evaluating force constants from LCAO—MO—SCF electronic charge densities for diatomic molecules
Authors: Anderson Alfred B.
Published: February 2004

An approximate method is developed for evaluating quadratic stretching force constants for diatomic molecules. The method employs a component of the LCAO—MO—SCF electronic charge density which is centered on the heavier nucleus in a Poisson equation for the Born-Oppenheimer vibrational potential energy of the lighter nucleus. Several first row molecules are considered.