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1 Mar 1974

Volume 60, Issue 5, pp. 1699-2202

Page 1 of 4 Pages Next Page | Jump to Page

CO2 laser initiated decomposition of ethyl chloride

R. T. Bailey, F. R. Cruickshank, J. Farrell, D. S. Horne, A. M. North, P. B. Wilmot, and Tin Win

J. Chem. Phys. 60, 1699 (1974); http://dx.doi.org/10.1063/1.1681261 (6 pages) | Cited 6 times

Online Publication Date: 22 August 2003

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The decomposition of ethyl chloride (EtCl) has been studied at pressures in the range 0.2–100 torr in a CO2 laser beam (105–160 W cw) in order to evaluate the processes occurring in such a system. Selective excitation of the EtCl would lead to the observed CH4 production, but it is shown that ``proof'' of such a process is not readily attainable despite the well‐characterized thermal decomposition of EtCl in contrast with systems previously supposed to decompose selectively. The important effects of slight laser power irreproducibilities, induction periods and the high ``temperatures'' produced are discussed.

Effect of temperature on the rates of reaction of excess electrons in liquid hydrocarbons

G. Beck and J. K. Thomas

J. Chem. Phys. 60, 1705 (1974); http://dx.doi.org/10.1063/1.1681262 (2 pages) | Cited 5 times

Online Publication Date: 22 August 2003

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The effect of temperature on rates of reaction of electrons with biphenyl in n‐hexane, cyclopentane, and iso‐octane has been studied. The experimental data fit an Arrhenius plot of log k vs 1∕T giving activation energies of 6.4, 4.2, and 0.51 kcal∕mole, and A factors of 4.4 × 1016, 4.9 × 1015, and 3.2 × 1013 in n‐hexane, cyclopentane, and iso‐octane, respectively. The A factors for the reactions are discussed in terms of the quasi‐free nature of the electron.

Electron spin resonance of γ‐irradiated alkyl phosphates: The C2H5 radical in magnesium diethyl phosphate (MgDEP)

W. A. Bernhard and F. S. Ezra

J. Chem. Phys. 60, 1707 (1974); http://dx.doi.org/10.1063/1.1681263 (4 pages) | Cited 3 times

Online Publication Date: 22 August 2003

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The major free radical product trapped at 77°K in γ‐irradiated magnesium diethyl phosphate [((C2H5O)2PO2)2Mg] is the ethyl radical. The following principal values for the α and β proton hyperfine tensors were determined from ESR data obtained at the Q band: Axα = 15.9, Ayα = 20.6, Azα = 25.5; and Axβ = 26.0, Ayβ = 26.5, Azβ = 27.6±0.5 G. Significant reorientation of the ethyl radical occurs upon cleavage of the carbon oxygen bond. The assymetry in the α hyperfine tensor has been interpreted in terms of a twofold potential barrier to the rotation of the methylene group. Hindrance to the rotation of the methyl group, relative to the methylene, is apparent from differential line broadening within the spectrum at 77°K.

Electron spin resonance of γ‐irradiated alkyl phosphates: The CH3ĊHOP(O)2OC2H5− radical in magnesium diethyl phosphate (MgDEP)

F. S. Ezra and W. A. Bernhard

J. Chem. Phys. 60, 1711 (1974); http://dx.doi.org/10.1063/1.1681264 (6 pages)

Online Publication Date: 22 August 2003

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The free radical species observed by ESR after γ irradiation of magnesium diethyl phosphate (MgDEP) at 77°K and annealing to 160°K is Cmath3CHOP(O)2OC2H5−. The radical structure has been determined by deuterium and 13C substitution in polycrystalline samples and by a single crystal analysis. Hyperfine principal values for the α hydrogen, β hydrogen, and phosphorous nuclei are: (AzHα = −7.3 G, ‖ to C☒H bond; AxHα = −15.8 G, ‖ to p orbital; AyHα ∼ −27.5 G), (AzHβ = 25.2 G, ‖ to C☒C bond; AyHβ = 22.2 G; AxHβ = 22.8 G), and (AyP = 4.7 G, ‖ to p orbital; AzP = 6.1 G, ∼ ‖ to C ⋯ P direction; AxP = 2.8 G). From the temperature dependency of the phosphorous hyperfine coupling and the single crystal analysis, it is concluded that the predominant mechanism for transfer of spin to the phosphorous is hyperconjugation.

Absolute differential cross sections of elastically scattered electrons. V. O2 and CO2 at 500, 400, and 300 eV

J. Philip Bromberg

J. Chem. Phys. 60, 1717 (1974); http://dx.doi.org/10.1063/1.1681265 (5 pages) | Cited 25 times

Online Publication Date: 22 August 2003

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Absolute differential cross sections of electrons elastically scattered by O2 and CO2 were measured at energies of 500, 400, and 300 eV over the angular range of 2° to 40°. In both cases the cross sections become independent of the momentum change in the limit of small momentum change, and polarizabilities were calculated.

Time dependent effects in microwave spectroscopy: Theory and double resonance experiments on OCS

Steven R. Brown

J. Chem. Phys. 60, 1722 (1974); http://dx.doi.org/10.1063/1.1681266 (10 pages) | Cited 6 times

Online Publication Date: 22 August 2003

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The time dependence of the weak field microwave absorption spectrum of the J = 1 → 2 transition of OCS under amplitude modulated pumping of the J = 0 → 1 transition has been observed with submicrosecond resolution by using a 100 MHz bandwidth video spectrometer and a multichannel signal averager. In order to relate the observed time dependent power absorption to the dynamic process of rotational energy transfer a theory relating the power absorption and the energy level populations has been developed. It is found that the time variation of the power absorption is not simply proportional to time variation of the population difference between the two levels connected by the weak field. Equations are derived which describe the time evolution of these quantities immediately following inception and termination of the pump signal. It is found that, for practical reasons, the period immediately following termination of the pump signal is the best time to study collisional energy transfer. Observation of the pressure dependence of the absorption relaxation during this period led to a value of Pτ = 28.1 μ ⋅ μsec for the product of the pressure and the mean time between rotationally inelastic collisions.

Influence of the nuclear spin on the thermomagnetic torque

A. L. J. Burgmans, F. C. Wang, and T. W. Adair

J. Chem. Phys. 60, 1732 (1974); http://dx.doi.org/10.1063/1.1681267 (8 pages) | Cited 2 times

Online Publication Date: 22 August 2003

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The thermomagnetic torque in rarefied polyatomic gases is a result of the precession of the molecules around the direction of the external field. In the case of a strong magnetic field (Paschen‐Back regime) this precession is determined by the rotational angular momentum of the molecules. In weak magnetic fields the angular momentum of diamagnetic molecules is coupled to the nuclear spin which influences the molecular precession and thus the thermomagnetic torque. In this paper experiments on the thermomagnetic torque in HD, n‐D2, and n‐H2 are reported in both strong and weak magnetic fields. Large deviations from an H ∕ p behavior are found as a consequence of the spin coupling.

Laser photodetachment determination of the electron affinities of OH, NH2, NH, SO2, and S2

R. J. Celotta, R. A. Bennett, and J. L. Hall

J. Chem. Phys. 60, 1740 (1974); http://dx.doi.org/10.1063/1.1681268 (6 pages) | Cited 149 times

Online Publication Date: 22 August 2003

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Using a fixed frequency argon ion laser we have studied the energy spectra of electrons photodetached from OH−, NH2−, NH−, SO2−, and S2−. We determined the following electron affinities: EA(OH) = 1.829−0.014+0.010 eV, EA(NH2)=0.779±0.037 eV, EA(NH)=0.38±0.03 eV, EA(SO2)=1.097±0.036 eV, and EA(S2)=1.663±0.040 eV. Additionally, the angular distribution anisotropy parameter β was measured for OH− and NH2− at 4880 Å, as −0.993 ± 0.040, and 0.027±0.012, respectively, and information about negative ion vibrational constants is presented.

Influence of intramolecularly compensated dipoles upon collision absorption in liquids

S. Dasgupta and C. P. Smyth

J. Chem. Phys. 60, 1746 (1974); http://dx.doi.org/10.1063/1.1681269 (5 pages) | Cited 1 time

Online Publication Date: 22 August 2003

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Measurements of dielectric constant and dielectric loss at 0.22, 1.25, 3.22, and 10.00 cm have been made upon benzene, hexafluorobenzene, an equimolar mixture of benzene and hexafluorobenzene, a dilute solution of hexachlorobenzene in benzene, and hexane, dodecane, and octadecane. The very small sizes of the dielectric losses observed in this frequency region, where loss due to the rotational orientation of dipolar molecules of this size should be at or near a maximum, indicates the absence of any appreciable permanent molecular dipole moment. The increase of the loss values with increasing frequency in this region indicates that, as already established for benzene, they form the low‐frequency tail of a very‐far‐infrared absorption band for each liquid. The absorption presumably arises from the small temporary dipole moments induced by molecular collisions. It is found that the absorption coefficients are increased by the presence of mutually opposing and compensating permanent dipoles and of π electrons in the molecules.

High pressure laser Raman study of the dissociation of aqueous bisulfate ion

A. R. Davis, W. A. Adams, and M. J. McGuire

J. Chem. Phys. 60, 1751 (1974); http://dx.doi.org/10.1063/1.1681270 (3 pages) | Cited 1 time

Online Publication Date: 22 August 2003

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A three‐window optical cell has been designed and built to study the effects of pressure on the Raman spectra of corrosive liquids, gases, and solutions. The technique has been used to probe the effect of pressure on the dissociation of bisulfate ion in aqueous media. The relative changes of the dissociation constant with pressure are found to be in agreement with the results of high pressure conductivity measurements.

Raman spectra of gases. XI. Methyl torsional overtones in the ethyl halides

J. R. Durig, W. E. Bucy, L. A. Carreira, and C. J. Wurrey

J. Chem. Phys. 60, 1754 (1974); http://dx.doi.org/10.1063/1.1681271 (4 pages) | Cited 31 times

Online Publication Date: 22 August 2003

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A series of peaks in the Raman spectra of gaseous CH3CH3, CH3CH2Cl, CH3CH2Br, CH3CD2Br, CD3CH2Br, CD3CD2Br, CH3CH2I, CH3CD2I, and CD3CH2I have been observed and assigned to the torsional overtones, (Δν = 2) of the methyl group. From these spectroscopic data, barriers to internal rotation have been calculated for the ethyl halides. For the compounds where the barriers are accurately known from previous work, the values obtained in this study agree quite well. The value for the internal rotational barrier in ethyl iodide is 3.67 ± 0.01 kcal∕mole, which is considerably higher than the value previously reported from microwave studies. It is shown that Raman spectroscopy can be a convenient technique for obtaining torsional barrier heights when one uses the Δν = 2 quantum jumps of the torsional motion.

Molecular Zeeman effect in methyl fluoride

C. L. Norris, E. F. Pearson, and W. H. Flygare

J. Chem. Phys. 60, 1758 (1974); http://dx.doi.org/10.1063/1.1681272 (3 pages) | Cited 13 times

Online Publication Date: 22 August 2003

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Several rotational transitions in CH3F were observed at high magnetic fields to give the molecular g values of g⊥ = −0.062±0.002 and g∥=0.265±0.008, the magnetic susceptibility anisotropy of χ⊥−χ = (8.5±0.6)×10−6 erg/G2⋅mole, and molecular quadrupole moment along the C3 axis of Q∥ = (0.4 ± 1.0) × 10−2 6 esu ⋅ cm2. The value of g∥ in CH3F is compared to other molecules. The remaining Zeeman parameters are listed and discussed in light of the electronic structure.

Molecular Zeeman effect, electric dipole moment, and boron nuclear hyperfine coupling constants in HBS

E. F. Pearson, C. L. Norris, and W. H. Flygare

J. Chem. Phys. 60, 1761 (1974); http://dx.doi.org/10.1063/1.1681273 (4 pages) | Cited 13 times

Online Publication Date: 22 August 2003

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The zero‐field microwave spectra of the J =0 → J = 1 transitions in H11B32S, D11B32S, and D10B32S have been observed under high resolution to give the boron nuclear quadrupole coupling constants of eqQ = −3.72±0.03 MHz for 11B and eqQ = −7.91±0.03 MHz for 10B and the nuclear magnetic spin rotation constants along the axis perpendicular to the internuclear axis of M⊥ = −7.2±3.0 kHz for 11B and 1M⊥ = −2.6±1.0 kHz for 10B. The magnitude of the electric dipole moment was measured by high electric fields (Stark effect) to give ∣μ∣ = 1.298 ± 0.005 D. High magnetic fields (Zeeman effect) were used to measure the molecular g values and magnetic susceptibility anisotropies. The results are g⊥ = −0.0414±0.0002 and χ⊥−χ∥ = 7.2±0.5×10−6 erg/G2⋅mole for H11B32S and g⊥ = −0.0356±0.0002 and χ⊥−χ∥ = 9.8±2.1×10−6 erg/G2⋅mole for D11B32S. The resultant molecular electric quadrupole moment is Q∥ =2.7±0.6 × 10−26 esu ⋅ cm2 and the g values from the H11B32S☒D11B32S isotopic pair were used to determine the sign of the electric dipole moment, + HBS −.

Theoretical foundations of purely semiempirical quantum chemistry

Karl F. Freed

J. Chem. Phys. 60, 1765 (1974); http://dx.doi.org/10.1063/1.1681274 (24 pages) | Cited 68 times

Online Publication Date: 22 August 2003

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All the purely semiempirical quantum chemical theories of molecular electronic structure, such as the Pariser‐Parr‐Pople theory and its all valence electron generalizations like MINDO, assume the existence of an abstract true effective Hamiltonian which acts only within the space spanned by a minimum basis set of valence shell orbitals. Instead of following the customary procedure of attempting to determine the properties of this true effective Hamiltonian by fitting its matrix elements to experiment, this effective Hamiltonian is derived from the full N‐electron molecular Schrödinger equation under the condition that a complete configuration interaction calculation within the valence shell using this true effective Hamiltonian reproduces the exact ground and valence state energies. It is shown that this true effective Hamiltonian also exactly reproduces the projection of the exact ground and valence state wavefunctions on the space spanned by the minimum valence shell basis in the fixed core approximation. Explicit expressions are presented enabling the ab initio evaluation of the matrix elements of this true effective Hamiltonian in the valence shell basis, the true parameters. A discussion is presented of how these true parameters may be evaluated by slight modifications of standard methods such as degenerate Rayleigh‐Schrödinger perturbation theory (linked cluster form), Nesbet's hierarchy method, and related cluster function approaches. For the first time, this enables the ab initio evaluation of the true parameters which are empiricized in the semiempirical theories, thereby providing systematic methods for the testing of all of the assumptions of these semiempirical theories and for the development of new and improved parametrization schemes. A detailed discussion is also given concerning the nonclassical aspects of the true parameters.

Selection of self‐consistent‐field orbitals

T. L. Gilbert

J. Chem. Phys. 60, 1789 (1974); http://dx.doi.org/10.1063/1.1681275 (3 pages) | Cited 7 times

Online Publication Date: 22 August 2003

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A procedure introduced by Davidson for selecting orbital bases on the occupied and virtual Hartree‐Fock manifolds is shown to be equivalent to a procedure introduced by Adams.

Dielectric relaxation in water in the neighborhood of 4°C

E. H. Grant and R. J. Sheppard

J. Chem. Phys. 60, 1792 (1974); http://dx.doi.org/10.1063/1.1681276 (5 pages) | Cited 11 times

Online Publication Date: 22 August 2003

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The complex permittivity of water has been measured at seven temperatures between 3 and 5°C over a frequency range of 0.4–4 GHz. The data are analyzed first in terms of a small but significant distribution of relaxation times of magnitude larger than that observed previously and then as two separate Debye process having relaxation times separated by a factor of ∼2. It is shown that one possible interpretation of these observations is that a bond breaking process takes place in which the rate of formation of one bonded molecules from two bonded molecules depends upon whether the latter are bonded symmetrically or unsymmetrically. The value of the high frequency permittivity (ϵ∞) calculated from this model is shown to agree well with experiment. There is no evidence of any abrupt changes (``kinks'') greater than random experimental error in the temperature variation of the dielectric parameters of water between 3–5°C.

Absorption spectra of Mo atoms isolated in rare‐gas matrices

David W. Green and Dieter M. Gruen

J. Chem. Phys. 60, 1797 (1974); http://dx.doi.org/10.1063/1.1681277 (5 pages) | Cited 13 times

Online Publication Date: 22 August 2003

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The ultraviolet spectra of Mo isolated in Ar, Kr, and Xe matrices at 14°K have been correlated with the gas phase spectra. Contrary to the interpretations of the spectra of the P ← S transitions of a number of matrix isolated atoms, no crystal field effects leading to a breaking of the orbital degeneracy are required in order to obtain a satisfactory explanation of the spectra. The different matrices affect the spin‐orbit coupling and configuration interaction of the Mo atom leading to changes in the triplet splittings of the y7P ← a7S transition. The diffusion of Mo atoms in an Ar matrix lead to the formation of polymers. No definitive assignment of bands to the dimer could be made.

Energy limits in chemiluminescent, atom transfer reactions: Bond dissociation energy of NaF

David O. Ham

J. Chem. Phys. 60, 1802 (1974); http://dx.doi.org/10.1063/1.1681278 (4 pages) | Cited 15 times

Online Publication Date: 22 August 2003

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Atomic emissions from the reactions M2 + X → MX + M* have been observed for the systems which produce MX = NaF, NaCl, NaBr, KCl, and KBr. Energy limits in these reactions are also discussed which yield lower limits on values of D00(MX) and a value of D00(NAF) = 123±3 kcal/mole is recommended. Arguments are presented in support of previous chemiluminescence determinations of bond energy limits.

High resolution photodetachment study of OH− and OD− in the threshold region 7000–6450 Å

H. Hotop, T. A. Patterson, and W. C. Lineberger

J. Chem. Phys. 60, 1806 (1974); http://dx.doi.org/10.1063/1.1681279 (7 pages) | Cited 70 times

Online Publication Date: 22 August 2003

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The photodetachment of OH− and OD− ions has been studied in the range 7000–6450 Å, utilizing a tunable, narrow‐bandwidth (0.5–1 Å) dye laser as the light source. A detailed comparison of the observed cross section with model calculations is made, yielding the following results: E.A.(OH)=(14 723±15) cm−1, E.A.(OD)=(14 703±15) cm−1. The observed isotope effect for the electron affinity can be ascribed almost entirely to differences in the position of the ground rotational state in OH(2Π3∕2) and OD(2Π3∕2); the implications of this result for the vibrational frequency of the negative ions are discussed. The energy dependence of the observed cross section indicates the influence of the electron‐permanent dipole moment interaction in the final channel on the threshold behavior, which is found to be sharper than that expected in the absence of such an interaction.

Light scattering due to spontaneous fluctuations in a binary reacting fluid mixture

Ming‐Nan Huang and W. H. Schwarz

J. Chem. Phys. 60, 1813 (1974); http://dx.doi.org/10.1063/1.1681280 (18 pages) | Cited 4 times

Online Publication Date: 22 August 2003

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Light scattered from a binary, viscous, heat conducting, diffusive, and reacting mixture by spontaneous fluctuations was theoretically examined using the hydrodynamical approach with a generalized form for Fick's law that was obtained by a thermodynamical theory based on the entropy inequality. An additional inertial‐diffusive term occurs in the diffusion equation and results in another Lorentzian contribution to the Rayleigh line and also adds to the non‐Lorentzian contribution to the Brillouin doublet. Explicit results for the autocorrelation functions and spectra are presented for (1) a binary, viscous, diffusive, thermally conducting mixture without reaction and (2) a binary, viscous, thermally conducting reacting mixture without diffusion. Comparison of the theoretical spectrum for a gaseous xenon‐helium mixture to experimental data demonstrates the importance of the inertial‐diffusive term and provides an explanation of the failure of the classical hydrodynamical theory. In addition, the case of acetic acid was treated as a reacting binary mixture of monomers and dimers, and the theoretically calculated Landau‐Plaszek ratio was compared to experimental data.

On the implication of the theory of Ichimaru: Physical properties of degenerate electron liquid

Madhu Jain and S. C. Jain

J. Chem. Phys. 60, 1831 (1974); http://dx.doi.org/10.1063/1.1681281 (6 pages)

Online Publication Date: 22 August 2003

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Calculations are performed for various physical quantities such as the pair correlation function, compressibility, etc., for an interacting electron liquid by solving the set of self‐consistent equations of the theory of Ichimaru. Comparison is made with other recent theories. It is found that even though being physically more sound, it does not give quite satisfactory results of g(r) and the compressibility sum rule in comparison to both the original theory of Singwi et al. and its modified version by Vashishta and Singwi. A modification in the theory of Ichimaru is discussed which may lead to remarkable improvement in the results.

HF infrared chemiluminescence, energy partitioning, and D(H☒GeH3) from the reaction of F atoms with germane

K. C. Kim, D. W. Setser, and C. M. Bogan

J. Chem. Phys. 60, 1837 (1974); http://dx.doi.org/10.1063/1.1681282 (5 pages) | Cited 15 times

Online Publication Date: 22 August 2003

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The infrared emission intensities from the reaction F+GeH4 have been used to measure the energy partitioned to the HF product. The experiments were conducted in a cold‐walled reactor with various flow rates of GeH4 and fluorine atom source (discharged SF6 or CF4). Based on the highest observed HF vibrational‐rotational level, D(H☒GeH3) was estimated as ≤78 kcal mole−1. The initial relative vibrational populations were N(ν = 1): N(ν = 2): N(ν = 3): N(ν = 4): N(ν = 5) = 0.10:0.18:0.29:0.41: 0.02. Based upon D(H☒GeH3) = 78 kcal mole−1, the mean fractional conversion of energy into HF vibrational energy was 0.58. The rotational distributions extend to quite high J levels; after correction for some rotational relaxation the mean fractional conversion to HF rotational energy was estimated as 0.12.

Study of the electron gas approximation

Yung Sik Kim and Roy G. Gordon

J. Chem. Phys. 60, 1842 (1974); http://dx.doi.org/10.1063/1.1681283 (9 pages) | Cited 116 times

Online Publication Date: 22 August 2003

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We test the applicability to atoms of the uniform electron gas energy expression in terms of the local atomic electron density. By using the known atomic electron densities obtained from an independent method (Hartree‐Fock) for the density in the electron gas energy expression, we calculate some atomic energies, one‐electron energies, and atomic ionization potentials and compare the results with the Hartree‐Fock energy values. We calculate the local kinetic energy and exchange energy densities in Hartree‐Fock atoms, and compare these results with the corresponding electron gas energy densities. We suggest a simple correction to the electron gas energy to be used for systems not paired in spin, and test this correction. We examine the effect of the finiteness of the atoms by treating a uniform electron gas with a finite number of electrons.

Coupled channel operators and rearrangement scattering. I. Comparative study of one‐state s‐wave e‐H scattering

Donald J. Kouri, Michael Craigie, and Don Secrest

J. Chem. Phys. 60, 1851 (1974); http://dx.doi.org/10.1063/1.1681284 (7 pages) | Cited 23 times

Online Publication Date: 22 August 2003

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Equations are derived for the amplitude density functions for the channel T matrix for rearrangement scattering. These equations are applied to electron‐hydrogen atom exchange scattering. A calculation is made in the one‐state approximation in which only the 1S state of hydrogen is considered. This calculation is compared with an earlier calculation using an alternate definition of the channel T matrix and with a number of other more complete s‐wave calculations. The new definition of the channel T matrix is shown to be superior to the earlier definition for numerical computation. The one‐state result is surprisingly accurate when compared to essentially exact variational results. This exceptional accuracy with such a limited basis is attributed to the fact that the formalism explicitly includes both the direct and the rearrangement channel descriptions.

Study of molecular reorientation: Pressure and temperature dependence of deuterium relaxation in liquid CDCl3

D. L. VanderHart

J. Chem. Phys. 60, 1858 (1974); http://dx.doi.org/10.1063/1.1681285 (13 pages) | Cited 29 times

Online Publication Date: 22 August 2003

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Deuterium NMR spin‐lattice relaxation measurements have been performed on the neat liquid CDCl3 over the range 28°C<T<165°C and at pressures up to 5 kbar (5×108 N∕m2). These measurements enable one to determine τθ,2, the correlation time for molecular reorientation about the axes perpendicular to the symmetry axis. The data are presented as a function of all three state variables, P, V, and T. An attempt is made to describe the data in terms of various simple models for reorientation including activation and free volume models. Each of these models predicts certain aspects of the data but fails in other areas. In particular, the activation model fails to predict the correct behavior at constant temperature and the free volume theories generally fail to predict the constant volume experiments. Deviations from the Debye and microviscosity theories are also noted. The mean time between collisions τcoll was calculated from τθ,2 assuming both Gordon's J‐diffusion model and the equivalence of τcoll and τJ, the angular momentum correlation time. These values of τcoll were then compared with the predictions of the cell model for liquids in which τcoll is simply the mean free path divided by the mean velocity. Generally, the data did not fit the cell model; however, at constant pressure, the cell model did predict the changes in τcoll quite well. Qualitative suggestions are made to account for the discrepancies. Finally, the possibility that H‐bonding exists in CHCl3 and affects the generality of these results by changing the quadrupole coupling constant and disturbing the dynamics of the system is discussed. It is concluded that these effects are small if they exist at all.
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