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15 Dec 1980

Volume 73, Issue 12, pp. 5909-6353

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Oxygen‐17 NMR and EPR studies of water exchange from the first coordination sphere of gadolinium(III) aquoion and gadolinium(III) propylenediaminetetra‐acetate

Rosalind V. Southwood‐Jones, William L. Earl, Kenneth E. Newman, and André E. Merbach

J. Chem. Phys. 73, 5909 (1980); http://dx.doi.org/10.1063/1.440148 (10 pages) | Cited 27 times

Online Publication Date: 14 July 2008

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The 17O NMR relaxation times, T1 and T2, for water in aqueous solutions of Gd(ClO4)3 and GdPDTA− and the EPR linewidths for the same complexes have been measured. These data are analyzed in terms of the Solomon‐Bloembergen‐Morgan equations for relaxation of a nucleus near a paramagnetic ion and McLachlan’s theory for average EPR relaxation times. The analysis results in a consistent set of physical parameters for the electron relaxation as well as kinetic constants for the water exchange from the complexes. The rate constant for water exchange at 298 K from the Gd(III) aquoion is 10.6×108 s−1 and for the remaining waters in the GdPDTA− complex is 3.3×108 s−1. These rates are higher than the previously published lower limits for water exchange from lanthanide aquoions. A comparison of these results with the rates of formation of other gadolinium complexes leads to the conclusion that the rate of water departure is not the rate limiting step in lanthanide complexation reactions with polydentate ligands.
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33.25.+k Nuclear resonance and relaxation
33.35.+r Electron resonance and relaxation

Intensities in pure rotational CARS of air

C. M. Roland and W. A. Steele

J. Chem. Phys. 73, 5919 (1980); http://dx.doi.org/10.1063/1.440149 (5 pages) | Cited 9 times

Online Publication Date: 14 July 2008

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Measurements of the pure rotational CARS spectrum of N2 and O2 in air are reported. The spectrum was obtained using a three‐color pulsed laser arrangement. Quantitative agreement between experiment and the calculated variations in intensity and line shape is obtained.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.70.Jg Line and band widths, shapes, and shifts

Band shapes in CARS: Background effects and overlapping resonances

C. M. Roland and W. A. Steele

J. Chem. Phys. 73, 5924 (1980); http://dx.doi.org/10.1063/1.440150 (9 pages) | Cited 3 times

Online Publication Date: 14 July 2008

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Quantitative intensity measurements are reported for the CARS spectra of the symmetric stretch (ν3) mode in liquid CH3I, the totally symmetric stretch (ν1) in liquid CCl4 and the Q branch for the vibration mode of gaseous N2 at a series of densities. Calculations of the observed band shapes were carried out for both polarized and depolarized bands of CH3I, for the band in CCl4 and for the N2 Q branch at the three lowest densities. Good agreement was obtained after the calculated band shapes were adjusted by varying the values chosen for the nonresonant susceptibility, and for the relaxation times of the vibrational normal coordinates and the reorientation (for the depolarized band). Relaxation times for the liquids and collision broadening factors for the gases are listed; in most cases, the values obtained are more accurate than the corresponding numbers from spontaneous Raman spectra. The problems involved in calculating CARS intensities in the presence of nonresonant susceptibility and overlapping resonances are discussed.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.70.Jg Line and band widths, shapes, and shifts

Mechanical characteristics and mechanism of the triboluminescence of fluorescent molecular crystals

B. P. Chandra and Jeffrey I. Zink

J. Chem. Phys. 73, 5933 (1980); http://dx.doi.org/10.1063/1.440151 (9 pages) | Cited 30 times

Online Publication Date: 14 July 2008

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The mechanical characteristics of triboluminescence (TL) from coumarin, acenaphthene, resorcinol, phenanthrene, and m‐aminophenol crystals are studied. The TL spectra of these crystals resemble their fluorescence spectra. The TL appears concurrently with the sudden force decreases in the fracture regions of the force vs compression curves of the crystals. The decay time of TL from the motion of a single crack is of the order of a microsecond. The dependence of the TL intensity on time, impact velocity, the applied stress, and the crystal dimensions is discussed quantitatively using a phenomenological theory based on the movement and interaction of cracks in the crystals. No systematic correlation of the normalized TL intensity with the photoluminescence efficiency, charge produced during crystal fracture, or the experimental fracture stress is found. No considerable differences are found between the TL intensities of crystals grown in argon and in nitrogen atmospheres when they are crushed inside argon‐stripped liquid or in air. Triboluminescence is an intrinsic property of the crystals and is discussed in terms of the piezoelectrification produced during the movement of cracks in the crystals.
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78.60.Mq Sonoluminescence, triboluminescence
62.20.-x Mechanical properties of solids

Extension of the matrix theory of circular dichroism for unordered polypeptides

David A. Rabenold

J. Chem. Phys. 73, 5942 (1980); http://dx.doi.org/10.1063/1.440152 (5 pages) | Cited 8 times

Online Publication Date: 14 July 2008

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A Green operator technique used within a susceptibility framework is employed to present a unified theory for the circular dichroism of unordered polypeptides. The theory includes ground state wave function corrections. Two limiting cases of the formulation are the matrix theory of CD and a generalization of the rotational strength expressions derived by Tinoco [Adv. Chem. Phys. 4, 113 (1962)].
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87.15.M- Spectra of biomolecules

On the quantitation of light emission from cytochrome c in the low quantum yield limit

P. M. Champion and R. Lange

J. Chem. Phys. 73, 5947 (1980); http://dx.doi.org/10.1063/1.440153 (11 pages) | Cited 32 times

Online Publication Date: 14 July 2008

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A method for the quantitation of light emission is presented which uses the Raman scattering cross section of water as a reference. The method is successfully applied to systems having a known quantum yield, thus providing an independent check of Raman cross‐section measurements. A very weak incoherent emission from the ferrocytochrome c system is quantitated (Φ=3.6×10−6) and interpreted using a simple kinetic model which is consistent with the quantum mechanical treatment. The quantum yield measurements imply that the excited state (S1) lifetime of the ferrocytochrome is on the order of 0.2 ps, while the lifetime of the ferricytochrome is deduced to be much shorter. The implications of these measurements concerning the magnitudes of the excited state (S1, S2) damping factors in ferrocytochrome c are also discussed.
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87.15.M- Spectra of biomolecules
33.50.Dq Fluorescence and phosphorescence spectra

Picosecond kinetics of acridine in solution

S. L. Shapiro and K. R. Winn

J. Chem. Phys. 73, 5958 (1980); http://dx.doi.org/10.1063/1.440154 (5 pages) | Cited 6 times

Online Publication Date: 14 July 2008

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The fluorescence lifetime of acridine depends upon the excitation and emission wavelengths in certain solvents. The lifetime is also a sensitive function of temperature and medium, and variations are interpreted in terms of the hydrogen bonding characteristics of the solvents.
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33.50.Dq Fluorescence and phosphorescence spectra
78.55.Kz Solid organic materials
78.55.Bq Liquids

ESR studies on cation‐radicals of simple olefins and dienes produced in γ‐irradiated frozen solutions of trichlorofluoromethane

Tadamasa Shida, Yoshikazu Egawa, Hideo Kubodera, and Tatsuhisa Kato

J. Chem. Phys. 73, 5963 (1980); http://dx.doi.org/10.1063/1.440155 (8 pages) | Cited 56 times

Online Publication Date: 14 July 2008

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Cation radicals of butene‐1, trans and cis butene‐2, isobutene, tetramethylethylene, cyclopentene, cyclohexene, butadiene, 1,3‐pentadiene, cyclopentadiene, 1,3‐ and 1,4‐cyclohexadienes have been produced mostly for the first time in γ‐irradiated frozen matrix of trichlorofluoromethane at 77 K. Well resolved ESR spectra at 77 K or at 130–155 K permit the determination of proton hyperfine coupling constants. Large hyperfine coupling constants of methylene and methyl protons adjacent to π electron systems indicate an extensive hyperconjugation in the cations. The following photoisomerizations are found: butene‐1+→butene‐2+, cyclopentene+→1,3‐pentadiene+, 1,4‐cyclohexadiene+→ 1,3‐cyclohexadiene+, 1,3‐cyclohexadiene+→1,3,5‐hexatriene+. The nonplanar cations of cyclopentene and 1,3‐cyclohexadiene undergo puckering motion in a limitedly warmed matrix. In the warmed matrix, where diffusions of the cation radicals toward unreacted hydrocarbon molecules proceed slowly, proton transfer reactions are induced. Decisive evidence for the formation of dimer cations is not obtained under the conditions studied.
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82.50.-m Photochemistry
76.30.Rn Free radicals

The coil–globule transition: Radius of gyration of polystyrene in cyclohexane

Shao‐Tang Sun, Izumi Nishio, Gerald Swislow, and Toyoichi Tanaka

J. Chem. Phys. 73, 5971 (1980); http://dx.doi.org/10.1063/1.440156 (5 pages) | Cited 117 times

Online Publication Date: 14 July 2008

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The temperature dependence of the radius of gyration of polystyrene (MW=2.6×107) in cyclohexane in the good through poor solvent regimes was obtained by analysis of the angular dependence of the autocorrelation function of light scattered from the solution. The observed transition in polymer dimensions through the coil to globule states is in good agreement with the predictions of mean field theory.
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36.20.Ey Conformation (statistics and dynamics)
36.20.Fz Constitution (chains and sequences)

Laser flash photolysis of benzene. III. Sn←S1 absorption of gaseous benzene

Nobuaki Nakashima, Haruo Inoue, Minoru Sumitani, and Keitaro Yoshihara

J. Chem. Phys. 73, 5976 (1980); http://dx.doi.org/10.1063/1.440131 (5 pages) | Cited 35 times

Online Publication Date: 14 July 2008

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Gaseous benzene was excited by a KrF excimer laser and a transient absorption was observed in the region between 210 and 930 nm. The Sn←S1 absorption spectrum is assigned using time‐resolved spectroscopy and the effects of foreign gas. Three peaks have been found and are assigned as follows: 545 nm(1E1u, f∼0.003), 400 nm (1 1E2g, f∼0.02), and 267 nm (2 1E2g, f∼0.08). The observed energies above the ground state are 7.8 eV for the 1 1E2g state and 9.4 eV for the 2 1E2g state. Spectral shapes become sharper and each peak shifts to shorter wavelengths compared with those in cyclohexane solution. The results suggest that the 2 1E2g has a valence character. Other differences between the solution and gas spectra are discussed.
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33.20.Kf Visible spectra
33.20.Lg Ultraviolet spectra
82.50.Hp Processes caused by visible and UV light

High pressure study of luminescence from intramolecular CT compounds

A. M. Rollinson and H. G. Drickamer

J. Chem. Phys. 73, 5981 (1980); http://dx.doi.org/10.1063/1.440132 (16 pages) | Cited 23 times

Online Publication Date: 14 July 2008

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The effects of high pressure on the luminescence properties of four organic intramolecular charge transfer compounds were investigated. The compounds were studied in a wide range of liquid and polymeric environments, and for one of the compounds, the effect of chemical substitution was also examined. In general, an increase of pressure affects the luminescence in a way which is in some degree similar to an increase of solvent polarity. A single configuration coordinate model was used to interpret the luminescence in terms of excited state interactions. Three of the compounds exhibited only fluorescence: p‐(9‐anthryl)‐dimethylaniline (ADMA), 6‐propionyl‐2‐dimethylaminonaphthalene (PRODAN), and 1‐anilino‐8‐naphthalenesulfonate (ANS). Fluorescence from the first two compounds in nonpolar media is attributed to an excited state relatively unaffected by the charge transfer process. In polar media, fluorescence is believed to originate from another excited state that possesses considerable charge transfer character, and whose energy is strongly influenced by solvent polarity. At high pressure, an apparent fluorescence shift to higher energy was observed in viscous alcohols apparently due to the introduction of fluorescence from the energetically higher lying non‐charge transfer excited state. This explanation is supported by the dual fluorescence decay observed from ADMA coincident with the sign reversal in fluorescence peak shift. Three excited states are believed to affect ANS fluorescence, two of them with charge transfer character. The model describing the excited states of ADMA and PRODAN is consistent with ANS fluorescence except in glycerol, whose anomalous behavior is discussed in the text. The fourth compound, nitroaniline, was studied in its three isomeric forms, with and without N‐methylation. In addition to affecting the phosphorescence and fluorescence of p‐nitroaniline, pressure studies indicate that nπ∗ singlet and triplet states figure prominently in the radiative and nonradiative processes of o‐nitroaniline and m‐nitroaniline as well.
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82.50.-m Photochemistry

The influence of a rare‐gas matrix on the electronic levels of isolated atoms

Frank Forstmann and Stefano Ossicini

J. Chem. Phys. 73, 5997 (1980); http://dx.doi.org/10.1063/1.440133 (6 pages) | Cited 35 times

Online Publication Date: 14 July 2008

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A pseudopotential model is suggested for the calculation of the matrix perturbation on the spectra of isolated atoms. The calculated shifts of the ground state and of the excited state have different signs. The energy of the outer electron of the isolated atom is lowered in the substitutional site. A blue shift for the P←S absorption lines of the right magnitude is calculated for Cu, Ag, and Au atoms on substitutional sites in Ar, Kr, and Xe matrices.
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32.30.Jc Visible and ultraviolet spectra

Theory of deviations from the limiting near‐dissociation behavior of diatomic molecules

Robert J. Le Roy

J. Chem. Phys. 73, 6003 (1980); http://dx.doi.org/10.1063/1.440134 (10 pages) | Cited 37 times

Online Publication Date: 14 July 2008

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The nature of the deviations from the limiting near‐dissociation behavior of diatomic molecule properties is investigated. It is shown that for strongly bound species the leading deviations from the limiting behavior associated with the asymptotically dominant Cn/rn potential energy term can be quantitatively attributed to the higher inverse power terms contributing to the long‐range potential. The properties of the derived expressions show that experimental vibrational energies should often obey the limiting near‐dissociation equation even when the term Cn/rn is responsible for only a fraction of the potential strength at the levels’ outer turning points. In contrast, Bv values (and other properties) are quite sensitive to the presence of additional contributions to the long‐range potential, and deviations from their predicted limiting behavior should provide a sensitive new means of determining values of higher‐order potential coefficients. The theory is illustrated by and tested against results for B(3Π+0u)‐state I2 and for simple model potentials.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
82.20.Kh Potential energy surfaces for chemical reactions

19F nuclear magnetic shielding scale from gas phase studies

Cynthia J. Jameson, A. Keith Jameson, and Patricia M. Burrell

J. Chem. Phys. 73, 6013 (1980); http://dx.doi.org/10.1063/1.440135 (8 pages) | Cited 58 times

Online Publication Date: 14 July 2008

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By using results of density and temperature studies, 19F nuclear magnetic resonance frequencies measured in 20 gases of known densities are reduced to the zero‐density limit at 300 K. From these we obtain differences in shielding between rovibrationally averaged isolated molecules at this temperature. The magnitudes of the corrections linking the shielding in the liquid phase to the isolated molecule at its equilibrium configuration are discussed. These corrections are not necessarily small and are required in deriving an accurate absolute shielding of any molecule from the known absolute shielding of another molecule by observing the NMR chemical shift between the two.
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33.25.+k Nuclear resonance and relaxation

Sideband intensities in NMR spectra of samples spinning at the magic angle

Judith Herzfeld and Alan E. Berger

J. Chem. Phys. 73, 6021 (1980); http://dx.doi.org/10.1063/1.440136 (10 pages) | Cited 508 times

Online Publication Date: 14 July 2008

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General integral and series expressions are derived for the intensities of sidebands observed in the magic angle spectra of inhomogeneously broadened I=1/2 systems. The expressions are evaluated for a wide range of shift parameters and the results used to construct graphical and numerical methods for extracting the principal values of chemical shift tensors from the intensities of just a few sidebands. The methods are illustrated by application to 31P spectra of barium diethyl phosphate. The results agree well with previous single crystal measurements.
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76.60.Cq Chemical and Knight shifts
33.25.+k Nuclear resonance and relaxation

NMR relaxation study of Li+–Ni2+ interaction in aqueous solution

F. Hirata, H. L. Friedman, M. Holz, and H. G. Hertz

J. Chem. Phys. 73, 6031 (1980); http://dx.doi.org/10.1063/1.440137 (8 pages) | Cited 10 times

Online Publication Date: 14 July 2008

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The NMR relaxation of 7Li+ due to Ni2+ in aqueous solution as a function of magnetic field strength is experimentally determined and is calculated on tha basis of certain models for the ionic interactions. The results can be used to eliminate some models which are consistent with the osmotic coefficient data for aqueous LiCl, NiCl2, and their mixtures.
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33.25.+k Nuclear resonance and relaxation
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
76.60.Es Relaxation effects

Emission spectra and radiative lifetimes of the Cameron bands of CO trapped in solid rare gas matrices

J. Fournier, Hassan H. Mohammed, J. Deson, C. Vermeil, and J. Schamps

J. Chem. Phys. 73, 6039 (1980); http://dx.doi.org/10.1063/1.440138 (7 pages) | Cited 15 times

Online Publication Date: 14 July 2008

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The emission spectrum of the Cameron bands (a 3Π→X1 Σ+) of CO molecules trapped in solid Ne, Ar, and Kr has been studied using Xe resonance lamp excitation (λ=147 nm). The lifetime of the a 3Π state has been measured in solid Ne and found to be 90 msec. The decay time of this state is exponential within the range of experimental errors. The lifetime has been calculated assuming spin–orbit mixing between 1Σ+ and 3Π0 states, and found to be 94 msec for J=0. The lifetime values in Ar and Kr matrices are found to be 7.2 and <1 msec, respectively; this is consistent with the matrix shifts in solid Ne, Ar, and Kr, which for the 0–0 bands have been found to be −305, −946, and −2812 cm−1, respectively.
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33.20.Lg Ultraviolet spectra
33.70.Fd Absolute and relative line and band intensities

Circular intensity differential scattering of light by helical structures. II. Applications

Carlos Bustamante, Marcos F. Maestre, and Ignacio Tinoco

J. Chem. Phys. 73, 6046 (1980); http://dx.doi.org/10.1063/1.440139 (10 pages) | Cited 29 times

Online Publication Date: 14 July 2008

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Analysis and numerical calculations were made of the total scattering and differential scattering of circularly polarized light by helices as models of chiral structures. The differential scattering patterns are much more sensitive than the total scattering to helical parameters. For large helices the angular dependence of these patterns show lobes which alternate in sign. The number of lobes and the positions of the zeros directly measure the ratios of radius and pitch to wavelength. The signs depend on the sense of the helix. The results are compared with measured circular intensity differential scattering of membranes from the bacterium Spirillum serpens. Good qualitative agreement is obtained.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
87.15.M- Spectra of biomolecules

Angular distribution in the photoelectron spectrum of the ground and first excited vibrational bands of the X 2Σg+ state in N2+ measured as a function of photon energy

Thomas A. Carlson, Manfred O. Krause, David Mehaffy, James W. Taylor, Frederick A. Grimm, and John D. Allen

J. Chem. Phys. 73, 6056 (1980); http://dx.doi.org/10.1063/1.440140 (3 pages) | Cited 25 times

Online Publication Date: 14 July 2008

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Angle‐resolved photoelectron spectra were taken of the first ionization state of N2 as a function of photon energy using a monochromatized beam of polarized photons from the Wisconsin Synchrotron Radiation Center. From these results the angular parameters for the first two vibrational states were determined over a range of photon energies from 17.7 to 31.0 eV. In energy ranges where resonance absorption, accompanied by autoionization, is expected to occur, β for the first excited vibrational level (v1) was frequently characterized by near zero values. In energy regions free of discrete autoionization v1 was found to have a value of β considerably larger (∼0.4 to 0.8 units) than that for the ground vibrational level (v0). This result is shown to be in accordance with recent calculations by Dehmer et al., based on the effect of vibrational motion on β in the vicinity of a shape resonance.
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33.60.+q Photoelectron spectra

High resolution 1H solid state NMR studies of polyethyleneterephthalate

T. T. P. Cheung, B. C. Gerstein, L. M. Ryan, R. E. Taylor, and D. R. Dybowski

J. Chem. Phys. 73, 6059 (1980); http://dx.doi.org/10.1063/1.440141 (9 pages) | Cited 31 times

Online Publication Date: 14 July 2008

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Molecular motions and spatial properties of the solid polymer polyethyleneterephthalate have been investigated using high resolution 1H solid state NMR techniques. The longitudinal spin relaxation time T1ρ of protons (1H) in the rotating frame was measured for a spin locking field ranging from 5 to 20 G. The decay of the 1H magnetization indicated the existence of two distinct T1ρ’s and their field dependence shows that they are associated with two mobile phases of the polymer. The 1H magnetization also relaxes under the dipolar narrowed Carr–Purcell (DNCP) multipulse sequence with two dintinct T1y relaxation times. The ratios T1y’s and T1ρ’s deviate significantly from the expected theoretical values. The combined experiment with magic angle spinning and the DNCP sequence followed by homonuclear dipolar decoupling reveals the individual T1y relaxation of the resolved methylene and aromatic protons. These two species of protons were found to relax with the same T1y’s, thus implying that spin diffusion must have taken place under the homonuclear dipolar decoupling multipulse. The qualitative description of spin diffusion under homonuclear decoupling is given. The combined experiment with spin locking and the DNCP sequence yields the correspondence between the two T1ρ’s and the two T1y’s. The long T1ρ corresponds to the short T1y whereas the short T1ρ corresponds to the long T1y. Communication between the two spatial phases via spin diffusion was also observed in this experiment by monitoring the recovery of the 1H magnitization associated with the short T1ρ after it has been eliminated during the spin locking. The total 1H magnetization is allowed to equilibrate in the laboratory frame for a variable time much shorter than T1 after the spin locking field has been turned off. The spatial relationship between the two phases is discussed.
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76.60.Es Relaxation effects

Surface‐enhanced Raman spectroscopy of benzene and benzene‐d6 adsorbed on silver

M. Moskovits and D. P. DiLella

J. Chem. Phys. 73, 6068 (1980); http://dx.doi.org/10.1063/1.440142 (8 pages) | Cited 72 times

Online Publication Date: 14 July 2008

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The surface‐enhanced Raman spectrum of benzene and benzene‐d6 adsorbed on a silver film vapor‐deposited onto a low‐temperature substrate is reported. Many lines which correlate with Raman‐inactive and even infrared and Raman‐silent modes of the free molecule are observed with high intensity in the spectrum. The local symmetry which would cause those particular, otherwise inactive, vibrations to appear is C3v(σd), which corresponds to a benzene molecule lying flat atop an equilateral triangle of silver atoms so that the normals to three alternate edges of benzene point to the centers of the three atoms. An alternative explanation for the activity of these normally silent modes is presented which does not depend on the adsorption site symmetry but which postulates instead that an unusally steep electric field gradient exists near the surface of the metal which causes modes spanned by the same representations which span the elements of a third rank tensor A to become active. These, together with the vibrations which are normally Raman‐active in benzene, are the same vibrations which are Raman‐active in C3v(σd). An argument in support of the latter explanation is presented based upon the different response to excitation wavelength of the intensities of those modes which are active as a result of the polarizability tensor, α, as contrasted with those which become active because of A. An unequivocal choice between the two models cannot be made, however, on the basis of the data available.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Dititanium and divanadium

C. Cossé, M. Fouassier, T. Mejean, M. Tranquille, D. P. DiLella, and M. Moskovits

J. Chem. Phys. 73, 6076 (1980); http://dx.doi.org/10.1063/1.440143 (10 pages) | Cited 60 times

Online Publication Date: 14 July 2008

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The Ar+ laser‐excited spectrum of matrix‐isolated V2 consists of a resonance Raman progression with ωe=537.5 cm−1 and ωexe=4.2 cm−1. With increasing laser power several members of an anti‐Stokes progression and sequence components on both Stokes and anti‐Stokes members of this progression were observed and attributed to transitions originating from vibrationally excited stated populated as a result of laser irradiation. A second system with ωe=508 and ωexe=3.3 cm−1 also grew in with increasing laser power and 496.5 nm excitation. This was interpreted as a resonance Raman progression within an electronically excited state (A) of V2. The electronic resonance Raman spectrum corresponding to the A→X transition was also observed as well as one to another low‐lying electronic excited state. The v′=0 level of state A was found to lie 1860 cm−1 above the v″=0 level of the ground state. The multiple photon nature of the transitions discussed above was determined by performing laser power measurements. The resonance Raman spectrum of Ti2 was excited with HeNe and dye laser illumination in solid argon matrices containing titanium. As with V2, laser irradiation populated excited vibrational states of the ground state, producing an anti‐stokes, resonance Raman progression. Isotopic components of Ti2 were resolvable under high resolution, corroborating the assignment. A discussion of multiple bonding in transition metal dimers is presented which shows that the contribution of bonds originating from the atomic d orbitals do not always contribute uniformly to the metal–metal force constant. Hence the formal bond order is not always a good gauge of the bond strength of a transition metal dimer.
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33.20.Fb Raman and Rayleigh spectra (including optical scattering)
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Fm Bond strengths, dissociation energies

Spin–rotation and hyperfine parameters for the (001) excited vibrational state of NO2 from infrared–radiofrequency double resonance

M. Allegrini, A. R. W. McKellar, P. Pinson, and J. M. Brown

J. Chem. Phys. 73, 6086 (1980); http://dx.doi.org/10.1063/1.440144 (4 pages) | Cited 10 times

Online Publication Date: 14 July 2008

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Magnetic–dipole spin–rotation transitions within the ground and v3=1 excited vibrational states of 14N16O2 have been observed by the technique of infrared–radiofrequency double resonance, utilizing near coincidences between CO laser lines and NO2 ν3 band transitions around 6.2 μm. The ground state data contribute to the extensive body of microwave, EPR, and double resonance measurements now available for NO2. The excited state data are the first high resolution measurements within this state, and they are used here to determine a set of spin–rotation and hyperfine interaction parameters for NO2 in the v3=1 state.
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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.Ea Infrared spectra
33.20.Bx Radio-frequency and microwave spectra
33.15.Pw Fine and hyperfine structure

Effects of velocity averaging on the shapes of absorption lines

Herbert M. Pickett

J. Chem. Phys. 73, 6090 (1980); http://dx.doi.org/10.1063/1.440145 (5 pages) | Cited 60 times

Online Publication Date: 14 July 2008

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The velocity averaging of collision cross sections produces non‐Lorentz line shapes, even at densities where Doppler broadening is not apparent. The magnitude of the effects will be described using a model in which the collision broadening depends on a simple velocity power law. The effect of the modified profile on experimental measures of linewidth, shift and amplitude will be examined and an improved approximate line shape will be derived.
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34.90.+q Other topics in atomic and molecular collision processes and interactions (restricted to new topics in section 34)
33.70.Jg Line and band widths, shapes, and shifts
33.20.-t Molecular spectra

Three‐dimensional quantum mechanical studies of D+H2→HD+H reactive scattering. IV. Cross sections and rate constants with rotationally excited target molecules

J. C. Sun, B. H. Choi, R. T. Poe, and K. T. Tang

J. Chem. Phys. 73, 6095 (1980); http://dx.doi.org/10.1063/1.440146 (13 pages) | Cited 26 times

Online Publication Date: 14 July 2008

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The body fixed formulation of the adiabatic distorted wave theory is used to study the reactive collisions of the (D,H2) system. Cross sections are obtained on the ab initio potential surface from the threshold to 0.5 eV in relative translation energy for the case where the target molecule is in the first rotationally excited state. The present results of the ortho‐hydrogen are qualitatively similar to but quantitatively different from the previous results of para‐hydrogen. The statistically weighted cross sections and product state distributions are found in general agreement with the molecular beam experiment. The reaction rates are obtained by integration over the distribution function. From 150 to 750°K where there are experimental data, the curvature in the Arrhenius plot of the calculated rate constants is in excellent agreement with experiment. However, the absolute magnitudes of the rate constants are smaller than the experimental ones.
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34.50.Lf Chemical reactions
34.50.Fa Electronic excitation and ionization of atoms (including beam-foil excitation and ionization)
82.20.Pm Rate constants, reaction cross sections, and activation energies
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