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15 Jun 1977

Volume 66, Issue 12, pp. 5259-5832

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Infrared absorption spectra of gaseous HD. IV. Analysis of the collision‐induced fundamental band of the pure gas

S. Paddi Reddy and R. D. G. Prasad

J. Chem. Phys. 66, 5259 (1977); http://dx.doi.org/10.1063/1.433906 (10 pages) | Cited 6 times

Online Publication Date: 26 August 2008

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Studies of the infrared absorption spectra of the HD fundamental band in the pure gas, reported for the room temperature in Paper I of this series, have now been extended to temperatures 77 and 196 K. The spectra of the band were recorded for a number of gas densities up to 50 amagat. In addition to the usual collision‐induced broad features of the infrared fundamental band of a symmetric diatomic gas, these spectra at 77 and 196 K show the dipole‐allowed sharp R1(0) and R1(1) transitions owing to the individual molecules. Derived binary absorption coefficients of the collision‐induced band are (1.15±0.06) ×10−35 and (1.71±0.07) ×10−35 cm6 s−1 at 77 and 196 K, respectively. An analysis of the absorption profiles of the band at 77 and 196 K and those of the band at 298 K reported in Paper I was carried out, and the characteristic half‐width parameters δd and δc of the short‐range overlap‐induced transitions and δq (and δq′) of the long‐range quadrupole‐induced transitions are derived. The contributions of the overlap‐ and quadrupolar‐interactions to the absorption intensity of the band are separated by the method of profile analysis. The magnitude parameter λ and the range ρ of the overlap‐induced dipole moment for the HD–HD collision pairs are determined by obtaining the best fit of the calculated overlap part of the binary absorption coefficient as a function of temperature to the experimental values. Derived overlap parameters are λ=5.60×10−3, ρ=0.25 Å, and μ (σ) (the overlap‐induced dipole moment at the Lennard–Jones intermolecular diameter σ) =3.1×10−2 ea0.
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33.20.Ea Infrared spectra

Absolute coverage determination of CO on Ni(111)

W. Erley, K. Besocke, and H. Wagner

J. Chem. Phys. 66, 5269 (1977); http://dx.doi.org/10.1063/1.433907 (5 pages) | Cited 29 times

Online Publication Date: 26 August 2008

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The adsorption of CO on Ni(111) has been studied using LEED and calibrated Auger measurements in order to determine the absolute amount of adsorbed CO molecules. At room temperature and CO pressures of up to 1.3×10−3 Pa a saturation coverage of ϑCO?0.28, corresponding to 5.2×1014 molecules per cm2, has been obtained. This is contrary to the commonly accepted opinion that the saturation coverage of nondissociated CO on various transition metals should always amount to about 1×1015 molecules per cm2 irrespective of the underlying substrate structure.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Molecular beam Zeeman effect and dipole moment sign of ClF

Barbara Fabricant and J. S. Muenter

J. Chem. Phys. 66, 5274 (1977); http://dx.doi.org/10.1063/1.433908 (4 pages) | Cited 47 times

Online Publication Date: 26 August 2008

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Molecular beam electric resonance spectroscopy has been used to observe hyperfine, Stark, and Zeeman properties of chlorine monofluoride. The dipole moment from Zeeman data is 0.85(15), −FCl+, in agreement with the known magnitude. The sign obtained here is the opposite of earlier, less precise, Zeeman results but agrees with calculations and van der Waals molecule experiments. Hyperfine, Stark, and Zeeman properties for 35ClF and 37ClF are reported, including polarizability anisotropy, α∥−α⊥=1.32(8) Å3, molecular quadrupole moment, ϑ∥=1.54(7) ×10−26 esu⋅cm2, and the chlorine quadrupole coupling constant derivative, deQq/dR=−90(20) MHz/Å.
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33.55.+b Optical activity and dichroism
33.57.+c Magneto-optical and electro-optical spectra and effects
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Stark and Zeeman properties of ozone from molecular beam spectroscopy

Kenneth M. Mack and J. S. Muenter

J. Chem. Phys. 66, 5278 (1977); http://dx.doi.org/10.1063/1.433909 (6 pages) | Cited 40 times

Online Publication Date: 26 August 2008

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Stark and Stark–Zeeman transitions within single J states of ozone have been studied using molecular beam electric resonance spectroscopy. Results include dipole moment, μ; dipole moment of the first excited bending mode, μ (010); polarizability anisotropies, αaa−αbb and αaa−αcc; rotational magnetic moments, ga, gb, gc; magnetic susceptibility anisotropies, χaa−χbb and χaa−χcc; and quadrupole moment components, ϑaa, ϑbb, ϑcc. μ=0.5337(1) D, μ (010) =0.5261(1) D, αaa−αbb=2.82(1) Å3, αaa−αcc=2.63(4) Å3, gaa=2.98933(8), gbb=−0.22919(3), gcc=−0.07623(b), χaa−χbb=5.91(2) KHz/kg2, χaa −χcc=12.05(4) KHz/kg2, ϑaa=−1.4(2) ×10−26 esu⋅cm2, ϑbb=−0.7(2) ×10−26 esu⋅cm2, ϑcc=2.1(3) ×10−26 esu⋅cm2.
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33.55.+b Optical activity and dichroism
33.57.+c Magneto-optical and electro-optical spectra and effects
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

The optical absorption spectrum of stoichiometric neodymium nitrate hexahydrate

P. Caro, D.‐R. Svoronos, E. Antic, and M. Quarton

J. Chem. Phys. 66, 5284 (1977); http://dx.doi.org/10.1063/1.433910 (8 pages) | Cited 22 times

Online Publication Date: 26 August 2008

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The optical absorption spectrum of single crystals of neodymium nitrate hexahydrated with the stoichiometric composition (that is, without analytical excess of nitrogen) was recorded at 4.2 K between 10 000 and 33 000 cm−1. The theoretical analysis was undertaken through a computer program which takes into account free‐atom classical operators, including two‐ and three‐body operators, as well as a crystal‐field operator written in the approximate C3v symmetry of the truncated icosahedron which makes the tencorners coordination polyhedron. The Hamiltonian was applied on the basis of the 364 ‖SLJMJ〉 kets in the 4f3 configuration, that is, including J mixing. The experimental sequence of 98 Stark levels from 28 2 S+1LJ levels was reproduced with a mean square deviation of 30 cm−1 out of an 18 adjustable parameters fit (12 free‐atom parameters and six crystal‐field ones).
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78.40.Ha Other nonmetallic inorganics

Electron spin resonance study of the radical Ph2Sb trapped in a single crystal matrix

M. Geoffroy, L. Ginet, and E. A. C. Lucken

J. Chem. Phys. 66, 5292 (1977); http://dx.doi.org/10.1063/1.433911 (4 pages) | Cited 2 times

Online Publication Date: 26 August 2008

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A radical formed by x‐irradiation of a single crystal of triphenylantimony is identified as Ph2Sb. Its ESR spectral parameters (for 121Sb) g1=1.9804, g2=2.1044, g3=1.9959, Tx=1270 MHz, Ty=−752 MHz, Tz=−699 MHz corrected for nuclear spin–orbit interactions and decomposed into isotropic (−60.3 MHz) and anisotropic (1330.3, −691.7, −638.7 MHz) components, and the nuclear quadrupole coupling constants e2Qqx=−101 MHz, e2Qqy=−205 MHz, e2Qqz=306 MHz, have been interpreted in terms of the radicals’s electronic structure and indicate that, like the analogous Ph2P and Ph2As radicals, the unpaired electron is localized on the 5pπ valence orbital of the antimony atom and that the radical is strongly bent, ∠CSbC≃98°.
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82.50.-m Photochemistry
76.30.Rn Free radicals

Velocity distribution of H(2s) resulting from the electron impact dissociation of H2 

Andrew U. Hazi and Karyn Wiemers

J. Chem. Phys. 66, 5296 (1977); http://dx.doi.org/10.1063/1.433912 (10 pages) | Cited 20 times

Online Publication Date: 26 August 2008

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We have calculated the velocity distribution of the fast, metastable hydrogen and deuterium atoms which result from the dissociation of the 1Πu(2pπu, 2sσg) autoionizing states of H2 and D2. The present model uses the previously computed potential energy curve and autoionization width of this doubly excited 1Πu state. The model treats the competition between ionization and dissociation into neutral fragments classically. In calculating the laboratory velocity distribution we take into account the thermal motion of the target molecules and the recoil due to the scattered electron. The effect of momentum transfer is important, as the calculated laboratory speed distribution depends sensitively on the angle of detection. The comparison of the experimental and the theoretical velocity distributions shows a significant discrepancy among the three measurements which have been reported to date.
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34.80.Gs Molecular excitation and ionization

Effect of collision‐induced phase shifts on the linewidths and line shifts of rotational spectral lines

Suresh C. Mehrotra and James E. Boggs

J. Chem. Phys. 66, 5306 (1977); http://dx.doi.org/10.1063/1.433913 (7 pages) | Cited 28 times

Online Publication Date: 26 August 2008

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A more general theory of the width and shift of microwave absorption lines is developed under the impact approximation with the effect of elastic as well as inelastic collisions being considered in a more rigorous way. Previous formulations (Anderson and Murphy–Boggs) are shown to be limiting cases of this treatment. The theory is applied to pure rotational transitions of the OCS–OCS, OCS–He, and OCS–Ar systems and the results compared with experiment. The agreement is very satisfactory for the quantum number dependence and temperature dependence of the linewidths and for the approximate magnitude of the pressure‐induced line shift.
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33.20.Bx Radio-frequency and microwave spectra
33.70.Jg Line and band widths, shapes, and shifts
34.50.Ez Rotational and vibrational energy transfer

Predissociation linewidths and level shifts for double‐curve crossing models

Michael L. Sink and André D. Bandrauk

J. Chem. Phys. 66, 5313 (1977); http://dx.doi.org/10.1063/1.433914 (12 pages) | Cited 32 times

Online Publication Date: 26 August 2008

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An analytic scattering model is applied to the problem of double‐curve crossings in predissociation. Analytic expressions are obtained for the energy shift ΔE and linewidth Γ by searching for poles in the scattering matrix. The validity of perturbation expressions for these parameters is examined by comparing numerical calculations of these expressions to our results. It is found that contributions from individual crossings are not always additive owing to interference effects.
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33.80.-b Photon interactions with molecules
31.70.Hq Time-dependent phenomena: excitation and relaxation processes, and reaction rates

Internal energy of CH+ produced by the C+(H2,H)CH+ reaction

C. A. Jones, K. L. Wendell, and W. S. Koski

J. Chem. Phys. 66, 5325 (1977); http://dx.doi.org/10.1063/1.433893 (5 pages) | Cited 20 times

Online Publication Date: 26 August 2008

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The energy spectrum of CH+ from the reaction C+(H2,H)CH+ was measured with a tandem mass spectrometer with improved energy resolution as a function of projectile kinetic energy. These spectra indicate the presence of the three lowest electronic states of CH+ and product vibrational excitation was observed in favorable cases. The internal energy distribution in the CH+ product was in satisfactory agreement with published results of phase space theory calculations for this reaction.
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82.20.Rp State to state energy transfer
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

14N PNQR investigation of the effect of pressure on phase transition in malononitrile

Avigdor Zussman and Eliezer Rapoport

J. Chem. Phys. 66, 5330 (1977); http://dx.doi.org/10.1063/1.433894 (5 pages) | Cited 5 times

Online Publication Date: 26 August 2008

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The 14N pure nuclear quadrupole resonance frequencies in the molecular crystal malononitrile were measured as a function of hydrostatic pressure up to 5.6 kbar. Above T=21.55°C, the second order phase transition previously studied by Zussman and Alexander was observed at high pressures. Above the transition pressure pc, each resonance line splits into two. The splittings Δν along an isotherm at 23°C were fitted to the equation Δν=B (p−pc)β and the critical exponent β was found to be close to 0.5. The variation of Tc with pressure was measured to 2 kbar and the line of transition could be described by the linear equation Tc(p) = 21.51+16.5734p. The present results for the variation of Δν along an isotherm were compared with previous results obtained along an isobar.
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64.70.K- Solid-solid transitions
62.50.-p High-pressure effects in solids and liquids
76.60.Gv Quadrupole resonance

The monomeric character of xenon hexafluoride vapor. The mass spectroscopy of noble gas binary fluorides and xenon oxide tetrafluoride

W. E. Falconer, M. J. Vasile, and F. A. Stevie

J. Chem. Phys. 66, 5335 (1977); http://dx.doi.org/10.1063/1.433895 (4 pages) | Cited 14 times

Online Publication Date: 26 August 2008

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Positive ion mass spectra have been obtained for KrF2, XeF2, XeF4, XeF6, and XeOF4 using 60 or 70 V electron impact ionization and a molecular beam source designed especially for reactive fluorides. Flight time distribution measurements have been made for neutral XeF6. Both these and the mass spectrometric fragmentation pattern indicate monomeric species in the saturated vapor. Associated (dimer) molecules can be obtained by isentropic expansion of XeF6; these are detected as dimer ions at one part in 104 of the monomeric ions in the mass spectrum. Electric deflection measurements on XeF6 vaporizing from inlets at temperatures from −19 to 40 °C showed no focusing effect.
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33.15.Ta Mass spectra

Optically detected magnetic resonance spectra of the lowest triplet states of benzophenone, 13C‐benzophenone, and three 4,4′‐dihalobenzophenones

John A. Mucha and David W. Pratt

J. Chem. Phys. 66, 5339 (1977); http://dx.doi.org/10.1063/1.433896 (17 pages) | Cited 35 times

Online Publication Date: 26 August 2008

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We describe measurements of the complete angular dependence of the optically detected magnetic resonance (ODMR) spectra of the lowest triplet states of benzophenone, carbonyl‐13C‐benzophenone, 4,4′‐difluorobenzophenone, 4,4′‐dichlorobenzophenone, and 4,4′‐dibromobenzophenone in 4,4′‐dibromodiphenylether host crystals at liquid helium temperatures. The principal axes and values of D (including the absolute signs) and g are reported and used to evaluate the spin–spin and spin–orbit contributions to the fine‐structure tensor of the parent molecule. It is found that the dipolar contributions to D in 3(n,π∗) benzophenone are at least a factor of 2 less than recent ab initio estimates of the spin–spin contributions to D in 3A2 formaldehyde. Carbon‐13 hyperdfine splittings have been observed in the ODMR spectra of 13C‐benzophenone; an analysis of these yields estimates of the orbital spin densities ρ2sC(O)?0.008 and ρ2pxC(O)?0.14 and suggests that the C1–C(O) –C1′ fragment is planar. The fine‐structure parameters of triplet benzophenone are strongly influenced by halogen atoms in the para ring positions. The ODMR spectra of the 4,4′‐difluoro and 4,4′‐dibromo derivatives also exhibit ring halogen atom hyperfine structure from which the estimate ρ2pπC4?0.10 is obtained. Taken together, the results of this investigation suggest that as much as 50% of the total spin density in the lowest triplet state of benzophenone itself resides on the aromatic rings, thereby accounting for the reduction in the dipolar contributions to D in the parent molecule and for the changes in the principal values (and directions) of D which occur in its heavy‐atom substituted derivatives.
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76.70.Hb Optically detected magnetic resonance (ODMR)
78.55.Kz Solid organic materials

Level‐anticrossing and cross‐relaxation effects in oriented molecular triplet states. 3(n,π∗) benzophenones in 4,4′‐dibromodiphenylether

John A. Mucha and David W. Pratt

J. Chem. Phys. 66, 5356 (1977); http://dx.doi.org/10.1063/1.433897 (12 pages) | Cited 23 times

Online Publication Date: 26 August 2008

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This paper reports the observation and analysis of magnetically induced changes in the phosphorescence intensities of triplet state benzophenone, carbonyl‐13C‐benzophenone, and three 4,4′‐dihalobenzophenones in single crystals of 4,4′‐dibromodiphenylether at 1.6°K. The signs, magnitudes, field positions, and widths of these changes can be interpreted in terms of two effects, anticrossings of two different electron–nuclear spin manifolds of the guest molecule and cross relaxation between the spin system of the guest and that of the host. At fields where anticrossings occur, the mixing between the spin states is strong and no hyperfine structure is observed. However, by comparing the results for the different molecules in the same host, it is shown that secular terms of the hyperfine interaction play a key role in determining the minimum spectral widths of the ’’transitions’’. At fields where cross relaxation predominates, the mixing between the spin states is weak and hyperfine and quadrupole splittings of both the guest and host can be resolved. The magnetic and optical parameters obtained by fitting the ’’spectra’’ are in excellent agreement with those determined by ODMR techniques [J. A. Mucha and D. W. Pratt J. Chem. Phys. 66, 5339 (1977), preceding paper]. Thus, experiments of this type can be utilized to provide information about the fine‐structure, g, hyperfine, and quadrupole tensors of emitting paramagnetic species in the complete absence of perturbing radiofrequency or microwave fields. Moreover, the systems described herein offer considerable promise in future studies of spin relaxation mechanisms in molecular solids by optical detection methods.
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76.70.Hb Optically detected magnetic resonance (ODMR)
78.55.Kz Solid organic materials

An analytically soluble model for the penetration of a two‐dimensional barrier: Quantal and semiclassical treatment

H. Massmann, K. Möhring, and P. Ring

J. Chem. Phys. 66, 5368 (1977); http://dx.doi.org/10.1063/1.433898 (12 pages) | Cited 6 times

Online Publication Date: 26 August 2008

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The reflection and transmission of a wave on a two‐dimensional barrier is studied quantum mechanically and semiclassically. The simple model consists of two degrees of freedom. One of them contains a barrier (of the Eckart type); the second allows only a bound motion in discrete quantum states. These two degrees of freedom are coupled. The transition probabilities for transitions between the different quantum states can, in the model considered here, be evaluated analytically, both quantum mechanically and semiclassically. Several of the so called uniform semiclassical approximations and also the initial value integral representation for the semiclassical transition amplitudes are considered and compared to the exact quantum mechanical results. Some new insight on the semiclassical treatment of the tunneling process is gained, specially concerning the proper choice of the integration path for the initial value integral representation of the transition amplitudes.
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03.65.Sq Semiclassical theories and applications
82.20.Fd Collision theories; trajectory models

Depolarized Rayleigh scattering in 10M amorphous and liquid KOH aqueous solutions

V. Mazzacurati, M. Nardone, and G. Signorelli

J. Chem. Phys. 66, 5380 (1977); http://dx.doi.org/10.1063/1.433899 (7 pages) | Cited 18 times

Online Publication Date: 26 August 2008

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An interpretation of the low frequency Raman scattering in all disordered systems including liquids is suggested in terms of phononlike excitations damped by anharmonicity and by structural relaxations. In principle, owing to the disorder‐induced breakdown of the k vector selection rule, all of these excitations are allowed to participate to the scattering process. An ad hoc simplified model is also proposed to calculate the low frequency Raman scattering, and it is found to reproduce at least qualitatively the main features of the depolarized spectrum in amorphous solid and liquid 10M KOH water solutions at different temperatures.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering

Dynamic effects in the scattering of electrons by small clusters of atoms

L. S. Bartell, B. Raoult, and G. Torchet

J. Chem. Phys. 66, 5387 (1977); http://dx.doi.org/10.1063/1.433900 (6 pages) | Cited 5 times

Online Publication Date: 26 August 2008

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Dynamic scattering corrections were calculated for 40 kV electrons diffracted by randomly oriented fcc clusters of argon and of gold atoms ranging in size from 13 to 135 atoms. Computations were carried out according to several variants of two limiting theoretical approaches, namely, the direct summing up of atomic contributions calculated through single–single and single–double scattered waves by modifications of Glauber theory, and the extrapolation to limitingly small crystallites of conventional dynamic theory in the Blackman and Fujimoto formulations. For the small clusters studied, integrated intensities of diffraction rings (through single–double scatterings) calculated for three dimensional crystallites differ insignificantly from Glauber theory intensities calculated by projecting atomic potential energies onto a plane perpendicular to the mean direction of the incident and scattered wave vectors. The fractional dynamic correction increases with cluster size very nearly as N2/3 in both the Glauber and Blackman–Fujimoto limiting treatments. For crystalline clusters 8–20 Å in diameter, the dynamic effect calculated by summing single–double scatterings is an order of magnitude larger than that according to Blackman–Fujimoto theory. For argon clusters the dynamic effect is not serious; but according to our direct sums, dynamic corrections for 16 Å spheres of gold are surprisingly large, exceeding 25% for 111 reflections. Since the direct sums have been verified experimentally for several vapor‐phase molecules, the present work indicates that, in the limit of very small scatterers, extrapolations from conventional two‐beam dynamic theory may seriously underestimate the magnitude of dynamic effects.
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34.80.Bm Elastic scattering
36.40.-c Atomic and molecular clusters

Molecular motions in compressed liquid heavy water at low temperatures

T. DeFries and J. Jonas

J. Chem. Phys. 66, 5393 (1977); http://dx.doi.org/10.1063/1.433901 (7 pages) | Cited 14 times

Online Publication Date: 26 August 2008

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The NMR deuteron spin–lattice relaxation times T1, self‐diffusion coefficients D, and shear viscosities η have been measured as a function of pressure in the temperature interval −15 to 10°C. The low‐pressure extreme of the measurements is Ice I, whereas Ice V represents the high‐pressure boundary of the experiments. In analogy with anomalous motional behavior in compressed liquid water, the initial compression of liquid D2O in the temperature interval studied results in higher motional freedom of D2O molecules so that T1 and D dependences with pressure exhibit a maximum and shear viscosity shows a minimum. This is a result of distortion and weakening of the hydrogen bond network owing to compression. Further compression hinders molecular motions as a result of increased repulsive interactions due to higher packing. This study also enables us to test the applicability of hydrodynamic equations at the molecular level for liquid heavy water. Analysis of the relaxation and shear viscosity data show that the Debye equation fails to describe the density effects on reorientation of D2O molecules. It appears that the success of the Debye equation to describe temperature effects on reorientation of H2O and D2O molecules at 1 bar is accidental. However, the data show that the deuteron relaxation rate (1/T1)D is proportional to η/T under isochoric conditions. The fact that the slope of the (1/T1)D vs η/T plot diminishes with increasing density indicates that compression leads to diminished coupling between rotational and translational motions of water molecules. The shear viscosity and self‐diffusion data show that the Stokes–Einstein equation does not represent the relationship between D and η in liquid heavy water. A brief discussion of the isotope effects on shear viscosity in liquid D2O and H2O is presented.
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76.60.Es Relaxation effects
66.10.C- Diffusion and thermal diffusion
62.10.+s Mechanical properties of liquids
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Diagrammatic perturbation theory: Many‐body effects in the X1Σ+ states of first‐row and second‐row diatomic hydrides

Stephen Wilson and David M. Silver

J. Chem. Phys. 66, 5400 (1977); http://dx.doi.org/10.1063/1.433902 (12 pages) | Cited 49 times

Online Publication Date: 26 August 2008

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Diagrammatic many‐body perturbation theory is employed in a study of the X1Σ+ states oif first‐ and second‐row diatomic hydrides at their respective equilibrium nuclear separations. All two‐, three‐, and four‐body terms are determined through third‐order in the energy within the algebraic approximation (i.e., parameterization of state functions by expansion in a finite basis). Padé approximants to the energy are constructed. From the first‐order wavefunction rigorous upper bounds to the expectation value of the electronic energy are obtained from the Rayleigh quotient. Two different zero‐order Hamiltonians are used, and the convergence properties of the resulting perturbation expansions are compared. In both schemes three‐ and four‐body terms are significant, having a magnitude that is as much as 24% of the sum of the second‐ and third‐order terms.
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31.15.V- Electron correlation calculations for atoms, ions and molecules

The potential energy curves of the X 1Σ+ and A 1Σ+ states of LiH 

William C. Stwalley, Warren T. Zemke, Kermit R. Way, Kwong C. Li, and Timothy R. Proctor

J. Chem. Phys. 66, 5412 (1977); http://dx.doi.org/10.1063/1.433903 (4 pages) | Cited 43 times

Online Publication Date: 26 August 2008

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As an important intermediate step in a long‐term project to fully understand the spectroscopy of the three lowest singlet states of LiH, (X 1Σ+, A 1Σ+, and B 1Π), we have constructed accurate hybrid potential energy curves for the X1Σ+ and A1Σ+ states to complement earlier work on the B1Π state. In each case the known Rydberg–Klein–Rees (RKR) for low vibrational levels was joined to the long‐range region of the potential (represented by new C6, C8, and C10 coefficients reported herein) fixed by the accurately known dissociation limits. The joining was obtained by scaling slightly the ab initio results of Docken and Hinze in the region of interpolation. Extrapolation to smaller distance was also done using ab initio results.
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34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
82.20.Kh Potential energy surfaces for chemical reactions

Product distributions for the ion–molecule reactions N++O2 and N3++O2

J. L. McCrumb and P. Warneck

J. Chem. Phys. 66, 5416 (1977); http://dx.doi.org/10.1063/1.433904 (7 pages) | Cited 15 times

Online Publication Date: 26 August 2008

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The title reactions were studied using a drift tube–mass spectrometer apparatus featuring preselection of injected primary ions. Measurements of the reduced mobilities of N+ and N3+ indicate experimental conditions such that the energies of the reacting ions are close to thermal (300 K). Rate coefficients obtained for the title reactions are k3=7.5×10−10 cm3 sec−1 for the reaction N++O2 and k6=7.7×10−11 cm3/sec−1 for the reaction N3++O2, in good agreement with literature values. Several other rate coefficients for reactions of N+, N2+, and N4+ ions are also in agreement with previous data. Altogether seven reactions had to be taken into account to derive the product distributions for the title reactions. The resulting product yields are 0.45, 0.41, 0.09 for the products O2+, NO+, and O+, respectively, from the N++O2 reaction; and 0.49, 0.65 for the products NO+ and NO2+, respectively, from the N3++O2 reactions.
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82.20.Hf Product distribution
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Stability of the equilibrium for atomic H in solid H2 

Gerald Rosen

J. Chem. Phys. 66, 5423 (1977); http://dx.doi.org/10.1063/1.433905 (5 pages) | Cited 8 times

Online Publication Date: 26 August 2008

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The previously reported phenomenological rate process theory for the storage of atomic hydrogen free radicals in a tritium‐impregnated crystalline molecular hydrogen solid is used to determine the dynamical stability of the constant uniform equilibrium solution. Our analysis indicates that the equilibrium is unstable (thus, unattainable experimentally) for storage temperatures in a certain range (specifically, 0.134 K≲T0≲0.80 K for 0.03% tritium by weight, 0.165 K≲T0≲0.80 K for 1.20% tritium by weight), while being absolutely stable with respect to arbitrary small‐amplitude perturbations for all storage temperatures below and above this range. The theory also predicts the maximum size for a stable H/H2 sample with an appreciable concentration of trapped H and a net excess rate of volumetric heating due to the tritium decay. These theoretical results are wholly consistent with the Webeler experiments performed to date.
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82.20.-w Chemical kinetics and dynamics
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

31P NMR studies of the linear chain magnets: Poly(metal phosphinates)

L. S. Smith, P. R. Newman, A. J. Heeger, A. F. Garito, H. D. Gillman, and Piero Nannelli

J. Chem. Phys. 66, 5428 (1977); http://dx.doi.org/10.1063/1.433915 (5 pages) | Cited 3 times

Online Publication Date: 26 August 2008

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The paramagnetic shift and linewidth of the 31P NMR have been measured for three isoelectronic magnetic polymers Co[OP (C4H9)2O]2, Cr[OP (CH3)2(C6H5)2O]OH, and Cr[OP (CH3)(C6H5)O] [OP (C8H17)2O] for 77⩽T⩽300 K. Analysis of the paramagnetic shift as a function of the static magnetic susceptibility yields a value for the hyperfine coupling constant A≈4×10−4 cm−1. Previously measured and calculated hyperfine constants for an electron in the 3s and 3p orbitals are used to show the paramagnetic shift is due mainly to transferred magnetic spin density (≈0.1%) in the phosphorus 3s orbital. The linewidths of these materials are approximately 10 Oe at room temperature and broaden slightly with decreasing temperature. The temperature dependences of the linewidths are used to deduce an upper limit (⩽1%) for the amount of transferred spin density in the phosphorus 3p orbital.
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76.60.Es Relaxation effects

High resolution 14N NMR in solids: Single crystals of ammonium hydrogen oxalate hemihydrate

E. K. Wolff, R. G. Griffin, and C. Watson

J. Chem. Phys. 66, 5433 (1977); http://dx.doi.org/10.1063/1.433916 (6 pages) | Cited 13 times

Online Publication Date: 26 August 2008

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Proton decoupled 14N NMR spectra of ammonium hydrogen oxalate (AHOX) single crystals have been employed to determine the electric field gradient tensor at the 14N sites. Despite the 99.4% abundance of 14N, the spectral lines are narrow (∼300 Hz) and show two inequivalent 14NH4+ ions with (e2qQ/h) =130 kHz, η=0.39 and (e2qQ/h) =350 kHz, η=0.27. On the basis of motional averaging arguments, we surmise that these nonvanishing field gradients arise primarily because of lattice distortions of the N–H distances. The results indicate that it should be relatively easy to obtain 14N spectra in single crystals, and thus to examine a number of phenomena which have heretofore been inaccessible.
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76.60.Es Relaxation effects

Temperature dependence of the laser enhanced reaction NO+O3(001) →NO2(2B1,2)+O2

Jerry Moy, Ezra Bar‐Ziv, and Robert J. Gordon

J. Chem. Phys. 66, 5439 (1977); http://dx.doi.org/10.1063/1.433917 (8 pages) | Cited 14 times

Online Publication Date: 26 August 2008

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The ratio of the rate coefficient of the vibrationally enhanced reaction NO+O3→NO2∗+O2 to the thermal rate coefficient was determined over the temperature range 155–303 K. This was accomplished by using a pulsed CO2 laser to excite the ozone molecules in a flow system. The enhancement of the rate coefficient was determined from the ratio of the laser‐induced chemiluminescent signal to the thermal dc signal and from the fraction of vibrationally excited O3 molecules in the gas mixture. The latter quantity was determined from measurements of laser beam attenuation in static gas mixtures, using the same cell and laser configuration. It was found that the activation energy was reduced by 1.29+0.25−0.22 kcal/mole or by 42±8% of the O3(001) vibrational energy, while the pre‐exponential factor was barely affected. The information theory of Levine and Bernstein predicts a much smaller reduction in the activation energy. On the other hand, the excitation function of Menzinger et al. indicates that an equivalent amount of translational (or rotational) energy would be 100% effective in reducing the observed activation energy.
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82.20.Pm Rate constants, reaction cross sections, and activation energies
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