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15 Jun 1989

Volume 90, Issue 12, pp. 6821-7615

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Vacuum ultraviolet laser spectra of ICl

R. H. Lipson and A. R. Hoy

J. Chem. Phys. 90, 6821 (1989); http://dx.doi.org/10.1063/1.456254 (6 pages) | Cited 12 times

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Vacuum ultraviolet fluorescence excitation spectra of jet cooled ICl have been recorded between 158 and 166 nm using a VUV ‘‘laser’’ generated by four‐wave sum‐mixing in Mg vapor. An unambiguous vibrational analysis of the spectra has shown that transitions from v″=0 of the ground state probe high vibrational levels of the first tier EO+ ion‐pair state between v′=245 and 360. Molecular constants obtained from both Dunham and near dissociation expansions are presented. Strong intensity modulation of the spectra was observed. Possible reasons for this effect are discussed.
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33.20.Ni Vacuum ultraviolet spectra
33.20.Tp Vibrational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants

An electron spin resonance study of the structure of CCl+4 radical cation in carbon tetrachloride γ‐irradiated at low temperatures by powder and single crystal analyses

Hachizo Muto, Keichi Nunome, and Machio Iwasaki

J. Chem. Phys. 90, 6827 (1989); http://dx.doi.org/10.1063/1.456255 (6 pages) | Cited 3 times

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The CCl+4 radical cation produced in CCl4 by γ irradiation at low temperatures was studied by electron spin resonance (ESR) spectroscopy to clarify the electronic structure. By combining an analysis of the angular dependence of ESR spectra in a single crystal plane with a spectral simulation of the powder pattern including the isotropic combinations of 35Cl and 37Cl atoms, it was found that two chlorine atoms are concerned in the radical, having different hyperfine coupling tensors of A(35Cl1)=11.2, 0.5, 1.3 mT and A(35Cl2)=6.2, 0.8, 1.8 mT. The g tensor is approximately axially symmetric and shows a large positive g⊥ shift (g=1.999, 2.10, 2.116), different from the rhombic g tensor of σ∗ dimer cations of alkyl halides and freons (gmax=2.04). The directions of the maximum hyperfine coupling of the two chlorine atoms Cl1 and Cl2 are close to each other and close to the gmin direction, though having a small deviation from the gmin direction by about 3°–10°. From a consideration on the g anisotropy combined with the optical absorption spectrum, the radical was suggested to be a Cl atom‐like species, in which one of the C–Cl bonds in the parent CCl+4 is released and the atom‐like chlorine nuclei formed makes a three electron bond [(σCl⋅⋅⋅Cl)2 (σ∗Cl⋅⋅⋅Cl)1] with a Cl atom in the released CCl+3 group. A discussion is given for the difference in the formation of the cationic species in CCl4 and the σ∗ dimer radical cation in the other alkyl halides.
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82.50.Kx Processes caused by X-rays or γ-rays
76.30.Rn Free radicals

Study of the ν6 band of CH3Br by infrared laser sideband and submillimeter‐wave spectroscopy

J. M. Chevalier, J. Legrand, P. Glorieux, G. Wlodarczak, and J. Demaison

J. Chem. Phys. 90, 6833 (1989); http://dx.doi.org/10.1063/1.456256 (7 pages) | Cited 2 times

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About 136 transitions in the ν6 band of CH3Br have been measured using an infrared laser sideband spectrometer. The sidebands were generated by mixing the 10 μm radiation of a CO2 laser with the radiation of a tunable high power microwave source. Frequencies of transitions with J≤71 and K≤8 are reported. The accuracy of the measurements is estimated to be better than 10 MHz. Some high J rotational transitions in the v6=1 state have also been measured with a submillimeter‐wave spectrometer. The new measurements have been combined with previous results to derive vibration–rotation parameters for the v6=1 state.
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33.20.Bx Radio-frequency and microwave spectra
33.20.Ea Infrared spectra
33.20.Vq Vibration-rotation analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants

Conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of fluoroacetyl chloride

J. R. Durig, H. V. Phan, J. A. Hardin, and T. S. Little

J. Chem. Phys. 90, 6840 (1989); http://dx.doi.org/10.1063/1.456257 (12 pages) | Cited 14 times

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The far infrared spectrum (375 to 35 cm−1) of gaseous fluoroacetyl chloride, CH2FC(O)C1, has been recorded at a resolution of 0.10 cm−1. The fundamental asymmetric torsions of the more stable trans (halogen atoms are trans) and the high energy cis conformations have been observed at 116.18 and 49.42 cm−1, respectively, each with several upper state transitions falling to lower frequency. From these spectral data, an asymmetric potential function has been calculated and the potential coefficients are: V1=43±6, V2=1039±36, V3=498±3, V4=149±21, and V6=−10±7 cm−1. The trans to cis and cis to trans barriers are 1455±25 cm−1 (4.16±0.07 kcal/mol) and 914±24 cm−1 (2.61±0.07 kcal/mol), respectively, with an enthalpy difference of 541±45 cm−1 (1.55±0.13 kcal/mol). From studies of the Raman spectra at variable temperatures, values of 509±37 cm−1 (1.46±0.10 kcal/mol) and 310±8 cm−1 (0.89±0.02 kcal/mol) have been determined for the enthalpy difference for the gas and liquid, respectively. The conformational stability, barriers to internal rotation, and fundamental vibrational frequencies which have been determined experimentally, are compared to those obtained from ab initio Hartree–Fock calculations employing both the 3‐21G∗ and 6‐31G∗ basis sets, and to the corresponding quantities obtained for some similar molecules.
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33.20.Ea Infrared spectra
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
33.20.Tp Vibrational analysis

Rotational analysis of math 2A1↔math 2E electronic transition of the jet‐cooled methylthio radical

Yen‐Chu Hsu, Xianming Liu, and Terry A. Miller

J. Chem. Phys. 90, 6852 (1989); http://dx.doi.org/10.1063/1.456258 (6 pages) | Cited 40 times

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A set of molecular parameters describing both the math and math states of CH3S, has been obtained by a joint fitting of the rotationally resolved electronic transitions observed in a free‐jet‐cooled laser‐induced fluorescence study of CH3S and an earlier microwave study of its math state. The present work shows that because of incomplete information, nearly all of the previously reported molecular parameters for CH3S must be significantly revised. The present observations show an unusual electronic structure for the radical, characterized by a short C–S bond distance and peculiar methyl group geometry in the ground state. The C–S bond is observed to lengthen markedly in the excited math state.
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33.50.Dq Fluorescence and phosphorescence spectra
33.20.Sn Rotational analysis
33.20.Bx Radio-frequency and microwave spectra

Hexamethylbenzene as a sensitive nuclear magnetic resonance probe for studying organic crystals and glasses

B. Jansen‐Glaw, E. Rössler, M. Taupitz, and H. M. Vieth

J. Chem. Phys. 90, 6858 (1989); http://dx.doi.org/10.1063/1.456259 (9 pages) | Cited 15 times

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Deuterated hexamethylbenzene (HMB) is used as a probe molecule for 2H NMR studies of the crystalline state of hexachlorobenzene and of several organic glasses. By measuring the spin–lattice relaxation and the line shape in the temperature range of 4–300 K the dynamical parameters of the molecular reorientation are investigated. For the system HMB/hexachlorobenzene, we find exponential relaxation and for the corresponding T1 an increase of its activation energy by a factor of 2 in comparison to the neat HMB. A homogeneous mixing of the guest and host molecules is found at least for guest concentrations up to 7%. In contrast, nonexponential spin–lattice relaxation is characteristic for all glass matrices, indicating motional heterogeneities. A log–Gauss distribution for the corresponding motional correlation times gives a good fit of the data. Its width parameter decreases linearly with temperature, while the mean correlation times are described by an Arrhenius law. The mean activation energy is reduced by a factor of about 3.5 as compared to neat HMB, demonstrating a loose packing of the molecules in the glass matrices.
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76.60.Es Relaxation effects

An investigation of the trimethylammonium chloride molecule in the vapor phase by pulsed‐nozzle, Fourier‐transform microwave spectroscopy

A. C. Legon and C. A. Rego

J. Chem. Phys. 90, 6867 (1989); http://dx.doi.org/10.1063/1.456260 (10 pages) | Cited 19 times

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The ground‐state rotational spectra of the symmetric‐top isotopomers [(CH3)314N, H35Cl], [(CH3)314N, D35Cl], [(CH3)315N, H35Cl], and [(CH3)315N, H37Cl] of a dimer formed between trimethylamine and hydrogen chloride have been observed in the vapor above heated samples of solid trimethylammonium chloride by pulsed‐nozzle, Fourier‐transform, microwave spectroscopy. Spectroscopic constants have been determined in each case and for [(CH3)314N, H35Cl] the values are B0=1800.4605(2) MHz, DJ=0.320(10) kHz, DJK=13.59(11) kHz, χ(35Cl)=−21.625(5) MHz, and χ(14N)=−3.504(5) MHz. The observed rotational constants B0 indicate that the nuclei N, H, and Cl lie along the C3 symmetry axis of the molecule in the order N⋅⋅⋅H⋅⋅⋅Cl with the distance r(N⋅⋅⋅Cl)=2.8164(3) Å. A comparison of the values of the nuclear quadrupole coupling constants χ(35Cl) and χ(14N) with those in related dimers and molecules leads to the evocation of some ionic character (CH3)3N +H Cl arising from a significant extent of proton transfer from Cl to N. This conclusion is reinforced when the values of χ(35Cl) and χ(14N) predicted on the basis of a recent electrostatic hydrogen‐bonded model (CH3)3N⋅⋅⋅HCl of the dimer are considered. The intermolecular stretching force constants kσ=84(3) N m−1 determined from DJ has a magnitude closer to that expected in the ion‐pair limit than in the hydrogen‐bond limit.
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33.20.Bx Radio-frequency and microwave spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Dj Interatomic distances and angles
36.40.-c Atomic and molecular clusters

Probability tables for small clusters of impurity atoms in sc, bcc, and fcc lattices assuming long‐range interaction

U. W. Pohl and W. Busse

J. Chem. Phys. 90, 6877 (1989); http://dx.doi.org/10.1063/1.456261 (4 pages) | Cited 15 times

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Powers and coefficients of polynomials describing the concentration dependent probabilities of small clusters of impurities are presented. For singles, pairs, and triples of impurities randomly distributed in simple cubic, body‐centered‐cubic, or face‐centered‐cubic host lattices, all interaction ranges between first next neighbor (1NN) and 8NN interaction are considered (singles and pairs up to 16 NN). The change of the probability functions with increasing interaction range is described. It is noted that an additional consideration of clusters with more impurities than a triple does not essentially improve the statistical error in the case of long‐range interaction. For the three lattices, empty shells and inequivalent lattice vectors are given.
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61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
61.72.Yx Interaction between different crystal defects; gettering effect

Collisional line shape for the rotational spectrum of methylcyanide: Experiments and theory

G. Buffa, D. Giulietti, M. Lucchesi, M. Martinelli, and O. Tarrini

J. Chem. Phys. 90, 6881 (1989); http://dx.doi.org/10.1063/1.456262 (6 pages) | Cited 5 times

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A collisional line‐shape study specialized in the rotational spectrum of CH3CN is presented. This system provides a test for pressure broadening and shift theories which has until now been hindered by inadequate theory and by experimental results at variance. New accurate measurements are presented which allow an explanation of the problem related to the reliability of experimental data. The thorough comparison made between measurements and an improved theory—obtained inside the frame of the Anderson–Tsao–Curnutte approximation—demonstrates the ripeness of the study of such rotational spectrum from both the experimental and theoretical points of view.
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33.20.Bx Radio-frequency and microwave spectra
33.70.Jg Line and band widths, shapes, and shifts

Infrared spectrum of sodium hydride

Arthur G. Maki and Wm. Bruce Olson

J. Chem. Phys. 90, 6887 (1989); http://dx.doi.org/10.1063/1.456263 (6 pages) | Cited 8 times

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The infrared spectrum of gaseous NaH from 886 to 1245 cm−1 has been measured with a resolution of 0.015 cm−1 at temperatures between 670 to 720 °C. The v=1←0, 2←1, and 3←2 transitions have been observed and combined with rotational transitions measured by others to obtain appropriate rovibrational constants and Dunham potential constants. The Herman–Wallis intensity effect has been measured in order to estimate a transition moment of 0.31±0.05 D for the v=1←0 transition.
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33.20.Ea Infrared spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors

Anisotropic reorientational relaxation of biphenyl: Transient grating optical Kerr effect measurements

F. W. Deeg, John J. Stankus, S. R. Greenfield, Vincent J. Newell, and M. D. Fayer

J. Chem. Phys. 90, 6893 (1989); http://dx.doi.org/10.1063/1.456264 (10 pages) | Cited 49 times

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Subpicosecond transient grating optical Kerr effect measurements have been used to evaluate the reorientation of biphenyl molecules in neat biphenyl and n‐heptane solutions. Besides an ultrafast (100 fs time scale) component associated with librational damping/dephasing, two reorientational relaxation components are observed. The slow reorientation is due to rotation around the short axes of the molecule (tumbling motion), the fast reorientation is associated with internal rotation around the central C–C bond and/or rotation of the whole molecule around its long axis (spinning motion). Whereas the tumbling motion has been observed in earlier depolarized light scattering data, the time resolved Kerr data presented here are the first ones to reveal the dynamics of the fast reorientation component and the ultrafast librational dynamics. It is shown that the diffusive reorientational relaxation must be coupled to the ultrafast librational dynamics, and implications of this coupling are pointed out.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
61.25.Em Molecular liquids
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

Time‐dependent theory of Raman scattering for systems with several excited electronic states: Application to a H+3 model system

Robert Heather and Horia Metiu

J. Chem. Phys. 90, 6903 (1989); http://dx.doi.org/10.1063/1.456265 (13 pages) | Cited 38 times

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The time‐dependent formulation of Raman scattering theory is used to study how nonadiabatic interactions affect the Raman spectrum of a model H+3 system, which has two excited electronic states. We start with a formula derived by Heller which gives the Raman scattering cross section as the Fourier transform (over time) of a time‐dependent overlap integral. The latter is calculated with a method proposed by Fleck, Morris, and Feit, and extended to curve crossing by Alvarellos and Metiu. In performing these calculations we are especially interested in displaying effects typical of systems having more than one upper state. If the incident laser populates two electronic states there are several ways (i.e., excite to state one and emit from state two, excite to state one, and emit from state one, etc.) by which the Raman process can reach a given final state, and this leads to quantum interference. This interference is manifested in the Raman cross section as approximate selection rules controlling which final states can be reached through the Raman process. These selection rules depend on the relative orientation of the transition dipoles that radiatively couple the ground electronic state with the excited electronic states. The magnitude of the nonadiabatic contribution to the Raman emission, e.g., the contribution from absorbing to state one and emitting from state two, can be determined from the polarization dependence of the Raman emission if the transition dipoles have neither parallel nor antiparallel relative orientation.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions

Transient photophysical hole‐burning spectroscopy of the hydrated electron: A quantum dynamical simulation

Kazi A. Motakabbir, Jürgen Schnitker, and Peter J. Rossky

J. Chem. Phys. 90, 6916 (1989); http://dx.doi.org/10.1063/1.456266 (9 pages) | Cited 19 times

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Results for the time‐dependent adiabatic eigenspectrum of an electron in water evolving in dynamic equilibrium have been obtained via quantum molecular dynamics simulation and used to evaluate the results expected from time‐resolved transient optical hole‐burning experiments. The dependence on excitation frequency and pulse length have been explored. The calculated results indicate that a relatively broad hole is created, but that, for ultrashort pump–probe time delays (≤100 fs) and comparably short pulses, the shape is distinctly different from the equilibrium spectrum. A slower component in the spectral evolution is also present, but appears likely to be difficult to distinguish experimentally. The shape of the absorption deficit is characteristic of the inhomogeneously broadened 1s, 2p‐type electronic state structure found previously to underlie the equilibrium spectrum, and distinguishes between this description and a number of proposed alternatives. With pulse durations comparable to the best now available, the phenomenon appears experimentally accessible.
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78.40.Dw Liquids
78.47.-p Spectroscopy of solid state dynamics

Ionization yields, total absorption, and dissociative photoionization cross sections of CH4 from 110 to 950 Å

James A. R. Samson, G. N. Haddad, T. Masuoka, P. N. Pareek, and D. A. L. Kilcoyne

J. Chem. Phys. 90, 6925 (1989); http://dx.doi.org/10.1063/1.456267 (8 pages) | Cited 45 times

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Absolute absorption and photoionization cross sections of methane have been measured with an accuracy of about 2% or 3% over most of the wavelength range from 950 to 110 Å. Also, dissociative photoionization cross sections were measured for the production of CH+4 , CH+3 , CH+2 , CH+, and C+ from their respective thresholds to 159 Å, and for H+ and H+2 measurements were made down to 240 Å. Fragmentation was observed at all excited ionic states of CH4.
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82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
33.80.Eh Autoionization, photoionization, and photodetachment
82.20.Pm Rate constants, reaction cross sections, and activation energies

Similarity transference of molecular parameters. II. The bond distances, force constants and polar tensors of HC3N and HC5N

O. M. Herrera, R. E. Bruns, and B. B. Neto

J. Chem. Phys. 90, 6933 (1989); http://dx.doi.org/10.1063/1.456268 (7 pages) | Cited 4 times

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The similarity transference procedure is extended to the calculations of the geometries and vibrational frequencies of HC3N and HC5N. Similarity models are constructed using the experimental and STO‐3G molecular orbital values of the bond distances and force constants of the HCN, C2H2, CH3CN, C4H2, CH3CCH, and C2N2 reference molecules. Simple linear regression calculations based on these similarity models and using STO‐3G values of the bond distances and force constants of HC3N result in estimates of the experimental bond distances and frequencies which have root mean square errors about an order of magnitude smaller than the one for the molecular orbital values. Similarity models for the bond distances and vibrational frequencies and intensities of HC5N are also reported.
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33.20.Tp Vibrational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Dj Interatomic distances and angles

Spectra, radiative lifetimes, and band oscillator strengths of the A 1Π–X 1Σ+ transition of BH

C. H. Douglass, H. H. Nelson, and Jane K. Rice

J. Chem. Phys. 90, 6940 (1989); http://dx.doi.org/10.1063/1.456269 (9 pages) | Cited 13 times

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We report new spectroscopic information on the A 1Π–X 1Σ+ transition of BH including the observation of the 0–1 and 1–2 bands using laser induced fluorescence (LIF) techniques. Ratios of Einstein coefficients, band oscillator strengths and transition probabilities have been obtained for the 0–1 compared to the 0–0 band and the 1–0 and 1–2 compared to the 1–1 band. These ratios indicate that the emission observed occurs predominantly within the diagonal elements. Additionally, the radiative lifetimes of the v′=0, 1, and 2 levels have been measured to be 127±10, 146±12, and 172±14 ns, respectively. Using the ratios above and the experimental lifetimes, we have obtained Einstein emission coefficients and band absorption oscillator strengths. These values are compared to several calculations from the literature and in some instances large differences are seen.
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33.50.Dq Fluorescence and phosphorescence spectra
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
33.70.Fd Absolute and relative line and band intensities

The structures and dipole moments of Ar–PF3 and Kr–PF3

Amine Taleb‐Bendiab, Marabeth S. LaBarge, Lawrence L. Lohr, Robert C. Taylor, Kurt W. Hillig, Robert L. Kuczkowski, and Robert K. Bohn

J. Chem. Phys. 90, 6949 (1989); http://dx.doi.org/10.1063/1.456270 (7 pages) | Cited 2 times

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The complexes of PF3 with Ar and Kr, were studied by Fourier transform microwave spectroscopy. The force constants and amplitudes of vibration for the van der Waals modes of the complexes and the average moments of inertia and structural parameters were estimated from the centrifugal distortion constants. The distance (Rc.m. )ave between the rare‐gas atom and the center of mass of PF3 is 3.959 Å for the Ar complex and 4.077 Å for Kr while the angle (θc.m. )ave between the Rc.m. vector and the C3 axis of the PF3 is 69.30° and 67.25°, respectively. The dipole moments of both complexes and of free PF3 were determined. The induced dipole components estimated for the rare gas using electric fields from ab initio calculations of PF3 agree with the experimental values for a conformation with the rare gas over a PF2 face. The PF2 face conformation is also consistent with the observed and ab initio estimates of the 83 Kr nuclear quadrupole coupling constant for the 83 Kr–PF3 species.
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36.40.-c Atomic and molecular clusters
33.20.Bx Radio-frequency and microwave spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Nondipole light scattering by partially oriented ensembles. II. Analytic algorithm

Duan Tian and W. M. McClain

J. Chem. Phys. 90, 6956 (1989); http://dx.doi.org/10.1063/1.456271 (9 pages) | Cited 2 times

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We consider the elastic single scattering of light from an ensemble of identical particles with nonrandom orientational distribution. The particle is modeled as an arbitrary rigid array of N dipole polarizabilities, and the polarizabilities within each particle interact through the retarded dipole–dipole tensor. We consider the scattering ensemble to be an ‘‘optical element’’ in the Müller formalism; thus its polarized scattering properties, both dipole and nondipole, are specified completely by a four‐by‐four Müller matrix M(ψ), where ψ is the scattering angle. In a previous work on orientationally random ensembles, the slow convergence of the nondipole elements suggested that they might be particularly sensitive to small orienting forces. This was confirmed by numerical calculations, which, however, also demonstrated the need for a faster analytic averaging algorithm. In this paper we extend the uniform distribution analytic algorithm to cases in which the orientation of the particles is specified by a general nonuniform distribution. We then specialize the general formula to the case of axially nonrandom orientation, such as might be caused by an external static electric field E operating on a permanent electric dipole of the model particle. We present an explicit algorithm for M(ψ,E) for this special case, together with an estimate of its computability. For models with just a few subunits, it should be computable by a desktop machine with four megabytes of memory. For more realistic models using 1000 subunits, the job can easily rise into the supercomputer range.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Electronic spectra of isolated cations in supersonic jets by mass‐selected ion‐dip spectroscopy. Cations of benzene, p‐difluorobenzene, and 1,3,5‐trifluorobenzene

Yuko Tsuchiya, Masaaki Fujii, and Mitsuo Ito

J. Chem. Phys. 90, 6965 (1989); http://dx.doi.org/10.1063/1.456272 (12 pages) | Cited 13 times

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The electronic transitions of the cations of benzene, p‐difluorobenzene (p‐DFB), and 1,3,5‐trifluorobenzene (1,3,5‐TFB) have been measured by mass‐selected ion‐dip spectroscopy which utilizes the dissociation of a parent cation in an excited state. This spectroscopy was successfully applied to the vibrational level selected cation in the ground electronic state which was prepared by 1+1 REMPI (resonant enhanced multiphoton ionization) of the neutral molecule in a supersonic jet. For all the cations, the spectra due to the transition from the ground state to the excited π,π state were observed. Ion‐dip spectra having sharp vibrational structures were found for p‐DFB and 1,3,5‐TFB cations, while a broad spectrum was observed for a benzene cation. It was also found that the vibrational structure of the ion‐dip spectrum of the 1,3,5‐TFB cation is quite different from that of the fluorescence excitation spectrum. The assignments of the ion‐dip spectra and dissociation mechanisms of the excited cations will be discussed.
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33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
33.20.Tp Vibrational analysis

Examination of CD3 vibrational structure by resonance Raman spectroscopy

S. G. Westre and P. B. Kelly

J. Chem. Phys. 90, 6977 (1989); http://dx.doi.org/10.1063/1.456273 (3 pages) | Cited 7 times

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The application of the resonance Raman spectroscopic method to the deuterated methyl radical is reported. Spectroscopic constants for CD3 are compared with previously reported values for CH3. The experimental and theoretical molecular physics of the methyl radical are discussed.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.15.Mt Rotation, vibration, and vibration-rotation constants

Fermi resonances between CH stretching and bending vibrations in CHF3, CHCl3, and (CF3)3CH

Esa Kauppi and Lauri Halonen

J. Chem. Phys. 90, 6980 (1989); http://dx.doi.org/10.1063/1.456681 (13 pages) | Cited 26 times

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A simple vibrational curvilinear internal coordinate Hamiltonian is used to account for Fermi resonance interactions between CH stretching and bending vibrations in CHF3, CHCl3, and (CF3)3CH. The eigenvalues of the Hamiltonian are obtained variationally with a Morse oscillator basis set for the stretch and two‐dimensional harmonic oscillator basis set for the bend. Five or six potential energy parameters are found to describe well the experimental CH stretching and bending overtone levels of the studied molecules. In the case of CHF3 the potential energy surface obtained is in good agreement with ab initio surfaces. A bond dipole model is used to calculate infrared absorption intensities for the transitions from the ground state to the totally symmetric excited states.
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33.20.Tp Vibrational analysis
33.20.Ea Infrared spectra

Vacuum ultraviolet–visible double resonance spectroscopy of NO. Observation of the high excited ns and nd Rydberg series

Asuka Fujii, Takayuki Ebata, and Mitsuo Ito

J. Chem. Phys. 90, 6993 (1989); http://dx.doi.org/10.1063/1.456274 (7 pages) | Cited 10 times

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The two‐color double resonance multiphoton ionization and fluorescence dip spectra due to the transitions from various rotational levels of the D 2Σ+ (v=1) state of NO to its high Rydberg states have been measured. Coherent vacuum ultraviolet (VUV) light generated by four wave mixing in Hg was used in the first excitation step. The ns(v=1) and nd(v=1) Rydberg series with 7≤n≤32 were observed. The rotational analysis for the d Rydberg series indicates that only the Π− component appears in the MPI spectra. A large dependence of the rotational constant upon n for the nd Π− Rydberg states was found and interpreted in terms of dΠ−–dΔ− mixing. An anomalous intensity distribution was also found for the rotational branches of the ns Rydberg states in the transition from the D 2Σ+ state. The anomaly is explained by the ns–(n−1)d mixing.
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33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
33.40.+f Multiple resonances (including double and higher-order resonance processes, such as double nuclear magnetic resonance, electron double resonance, and microwave optical double resonance)
33.20.Sn Rotational analysis

Calculation of vibration–rotation spectra for rare gas–HCl complexes

David C. Clary and David J. Nesbitt

J. Chem. Phys. 90, 7000 (1989); http://dx.doi.org/10.1063/1.456275 (14 pages) | Cited 52 times

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Calculations are described of spectra for the excitation of the bending and stretching vibrational–rotational energy levels in the van der Waals complexes of HCl with the rare gases Ne, Ar, Kr, and Xe. The calculations are performed using a basis set method, with distributed Gaussian functions being employed for the coordinate associated with the stretching of the rare gas atom. Intensities of combination and fundamental transitions for each of the low frequency modes are calculated for total angular momentum up to J=25. Surprisingly large intensities are predicted for transitions to states with multiple vibrations excited in the bending mode. Promising comparisons are obtained with infrared spectra measured recently for the complexes of HCl with Ne and Ar at low temperatures.
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36.40.-c Atomic and molecular clusters
33.20.Vq Vibration-rotation analysis
33.20.Ea Infrared spectra

Elastic constants of α‐CO by Brillouin spectroscopy

V. Askarpour, H. Kiefte, and M. J. Clouter

J. Chem. Phys. 90, 7014 (1989); http://dx.doi.org/10.1063/1.456276 (3 pages)

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The technique of Brillouin spectroscopy has been used to determine the adiabatic elastic constants of oriented single crystals of α‐CO at temperatures very close to the α–β phase transition. The values of the elastic constants at 60.9 K are c11=2.41, c12=1.44, and c44=1.06 (in units of 109 N m−2) and suggest that the k=0 acoustic phonon behavior is almost identical to that in a rare gas solid.
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62.20.D- Elasticity
64.60.Cn Order-disorder transformations

Free‐jet infrared absorption spectroscopy of rare gas–11BF3 complexes in the 7 μm region

Yoshiyasu Matsumoto, Yasuhiro Ohshima, Michio Takami, and Kozo Kuchitsu

J. Chem. Phys. 90, 7017 (1989); http://dx.doi.org/10.1063/1.456227 (5 pages) | Cited 16 times

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High‐resolution infrared absorption spectra of the van der Waals complexes of BF3 with a rare gas atom (Ne, Ar, and Kr) are obtained near the ν3 band of BF3 monomer in a supersonic free jet. Each spectrum shows a characteristic perpendicular band of a symmetric‐top molecule with C3v symmetry. The bands are shifted toward the red with respect to the monomer band by 0.3933(4), 1.7609(1), and 2.4059(4) cm−1 for NeBF3, ArBF3, and KrBF3, respectively. The Coriolis coupling constants of the complexes are almost identical to that of the monomer. These results show that complexing with a rare gas atom does not strongly influence the ν3 vibrational motion in BF3. The observed red shifts correlate well with the polarizabilities of the rare gas atoms. This finding is explained in terms of the instantaneous dipole–induced dipole interaction. The observed full widths of the Doppler‐limited spectral lines, typically 70 MHz, indicate that the lower limit of the vibrational predissociation lifetime is 2 ns.
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36.40.-c Atomic and molecular clusters
33.20.Ea Infrared spectra
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