摘要:

Inelastic differential scattering cross sections for collisions between potassium atoms and CH3I, C3H7I, CH3Cl, CF3I and HI are reported for the reduced scattering angle range from 20–1000 eV°. The measurements were made in the quasi-rectilinear trajectory regime using a velocity change method. Electronic excitation of the K atom accompanied by substantial vibronic excitation of the target molecule extending to the lower Rydberg states is seen in all the systems studied. The results are in accord with an electron harpoon model involving successive donation and recapture of an electron by the potassium atom. In the case of collisions leading to the ground electronic state of the molecule a doorway state similar, but not identical, to the molecular negative ion is involved and a model incorporating the effects of bond stretching—analogous to that advanced to interpret collision induced ionization in alkali metal + halogen molecule collisions—is in excellent agreement with the observations. Excited electronic states of the molecular target are believed to be populated by a similar mechanism involving excited ionic door-way states including one leading to C-H dissociation.

ISSN:0026-8976    

DOI:10.1080/00268978100100011

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The far-infrared absorption spectra of gaseous (298 K) and liquid (273 K, 233 K) SF6obtained by Rosenberg and Birnbaum [1] are analysed in terms of recent theoretical developments. Analysis of the band shape in the gas and liquid phases indicates that hexadecapole-induced absorption accounts only for the low frequency portion of the collision-induced band. The major part of the absorption can be attributed to a much shorter range mechanism such as anisotropic overlap. The resulting induced dipole which varies very rapidly with intermolecular separation and is consistent with a (7–28) interaction energy gives a good description of the liquid spectra. Collision-induced absorption and depolarized light scattering in SF6are compared. From a decomposition of the collision-induced gaseous spectrum, the value of the hexadecapolar energy, Φ2/σ9, is 2·7 × 10-24J (0·20 K) which yields a value of the hexadecapole moment, Φ, of 18 × 10-60C m4for σ = 0·468 nm.

ISSN:0026-8976    

DOI:10.1080/00268978100100021

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The dispersion energy between twoD3tris(butadienyl) metal complexes has been calculated over a range of mutual orientations for van der Waals contact and a set of larger intermolecular separations, for both anactivepair, Δ-Δ or Λ-Λ configurations, and aracemicormesopair, Δ-Λ configurations, by summing the pairwise coulombic potential between the transition charge density located on each atom of the first molecule with the corresponding density located on the individual atoms of the second molecule. The resonance term for energy transfer between two of theD3molecules in the lowest photoexcited state has been obtained for anactiveand aracemicpair over a similar range of mutual orientations and intermolecular separations. It is shown that the small but finite extension of dissymmetric molecules relative to the generally larger intermolecular separations cannot be neglected in chiral discriminations. The magnitude of observed chiral discriminations between correspondingactiveandracemicpairs are accounted for satisfactorily by the extended transition monopole model. Theoretically the chiral discrimination energy is found to be generally proportional toR-8at separations larger by an order of magnitude than the molecular dimensions.

ISSN:0026-8976    

DOI:10.1080/00268978100100031

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A new stability condition governing the formation of liquid crystalline phases of various degrees of orientational or translational ordering and supplementing the standard conditions of mechanical or thermal stability of a phase, is applied to the specific example of formation of a smecticAor a nematic phase from an isotropic phase. Numerical results are shown for a molecular model of hard spherocylinders with anr-6centre-to-centre attraction. Such molecules should form smecticAphases and the smectic range for which the stability breaks first, is of reasonable order of magnitude. The effect of temperature and the length of the molecule is examined.

ISSN:0026-8976    

DOI:10.1080/00268978100100041

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

An expression for the Einstein coefficient of spontaneous emission related to the pseudo-multipolar field, originally proposed by Jørgensen and Judd to account for hypersensitivity, is derived from the crystal field expansion due to point dipoles localized at the ligands. The expression is then successfully applied to the5D0→7F2,4,6transitions of the Eu3+ion. In a second part, the origin of the5D0→7F0transition is discussed and it is proposed that it can be accounted for by the pseudo-multipolar field whenJ-mixing is included.

ISSN:0026-8976    

DOI:10.1080/00268978100100051

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The incremental polarizability which occurs when two nitrogen molecules interact has been calculated by theab initiofinite field SCF method. For the configurations studied the [5s, 4p, 1d] gaussian basis set gives a potential surface which is in qualitative agreement with otherab initioestimates. At separations around the energy minimum the interaction α is well represented by the dipole-induced dipole model. At closer separations the deviations from DID behaviour are qualitively similar to those which occur in rare gas diatoms.

ISSN:0026-8976    

DOI:10.1080/00268978100100061

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The diffraction pattern of liquid carbon disulphide at 21°C has been measured with incident neutron wavelengths of 0·70 and 0·84 Å. The highQ-value data have been fitted to a molecular form factorf1(Q), and the derived bondlengths are in good agreement with other values. The inter-molecular contribution to the diffraction patternDM(Q) has been transformed to give a weighted total pair distribution functiondL(r) and combined with X-ray data to investigate orientational correlations.

ISSN:0026-8976    

DOI:10.1080/00268978100100071

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The dynamics of the reaction CO++NO→(NCO)++O have been studied over the relative energy range 3·5 to 10 eV. The reaction proceeds via a direct mechanism over the energy range studied. The effects of the barrier to reaction (due to the reaction endoergicity) on the reaction dynamics are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978100100081

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

We assume the time-averaged structure of a macroion solution to be determined only by the repulsive screened Coulomb pair potential between finite macroions. The counter ions and solvent are treated as a uniform neutralizing background which determines the screening of the potential. We slove the Ornstein-Zernike equation in the mean spherical approximation to obtain closed analytic forms for the direct correlation functionc(r) and the structure factorS(Q). In the zero charge limit, the Percus-Yevick hard sphere solution is recovered. As charge is added to the macroions at given volume fraction, the isothermal compressibility decreases andS(Q) shows increasing structure, eventually exhibiting solid-like behaviour. The results provide a useful model basis for studying interacting colloidal systems, and finite ion screened one component plasmas in general.

ISSN:0026-8976    

DOI:10.1080/00268978100100091

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Molecular motions have been studied in a powder sample of 1-cyanoadamantane, by using pulsed and continuous wave techniques, from 90 K to 480 K.

ISSN:0026-8976    

DOI:10.1080/00268978100100101

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor