Search

Approximate coupled channel scattering calculations are performed for model systems comprising a closed-shell atom colliding with rigid rotor diatomic homo- and hetero-nuclear molecules. Differential and total cross-sections for rotational scattering with several different interaction potentials are given for p-H2 and MuH + He, at a fixed total collision energy, and for LiF + Ar with a fixed emperical potential but varying collision energy. Conclusions are drawn concerning the effect on the cross-sections of the variations made.

Close-coupling calculations at 500 cm −1 for the system (Ar,LiH) are used to obtain scattering amplitudes and cross sections for the rotational transitions j = 1 to j' = 0, 2, 3, 4, 5, j = 2 to j' = 3 and j = 3 to j' = 4. The degeneracy-averaged cross sections are in reasonable agreement with experiment for two different simple model potentials. Values for m -dependent cross sections with respect to two frames of reference are compared with various rules for Δ m and with the previous results for (Ar,LiH).

To assist the interpretation of polarized rotational scattering experiments from states ( j, m ) to ( j, m' ), differential and total cross sections obtained from close-coupling calculations are given for m values corresponding to j ⩽ 3 in collisions between LiF and Ar at 20 cm −1 . The hypothesis ¦ m ¦-¦ m' ¦= 0 is proposed for the most likely transition, as an extension of the Δ m = 0 rule.

Calculations of the energies for various geometries of Li3, involving linear and perpendicular approaches of a Li atom to a Li2 molecule, are described. The basis set was of double zeta plus polarization contracted gaussian orbitals, and both a single configuration restricted Hartree—Fock function, and a five configuration function were used. The perpendicular approach was found to give the lowest energy, and the most stable form of Li3 is estimated to be about 10 kcal/mole lower in energy than Li + Li2.

Quasi-degenerate many-body perturbation theory with a multi-configuration reference space is used to obtain potential curves for the ground and excited electronic states of Li 2 , LiNa and Na 2 . Correlation contributions are analyzed and the effect of potential curve crossing on laser action is discussed.

A calculation by the self-consistent MO method of the UV spectra of thiophene, 2,2′-, 3,3′-, and 2,3′-dithienyl is described. For the dithienyls the local energy method developed by Longuet-Higgins and Murrell is applied. Only the π-electrons are considered explicitly and the zero differential overlap approximation is used. Values are given for the transition energies and oscillator strengths of thiophene, the dithienyls and some cyclopentadithiophenes, and for the angles of twist of the dithienyls in non-polar solution. For thiophene a reasonable charge distribution is obtained and the bond-orders lead to bond lengths in good agreement with experiment.

The gamma-ray spectrum of 2.3 day Np239 has been studied with high-resolution lithium-drifted germanium spectrometers, and twelve new gamma rays of low intensity have been identified. Ten of these are characterized as the de-excitation spectrum of a K= 1 2 band based at 469.8 keV in Pu239. The decoupling parameter (a) of this band is found to be 0.48. A comparison is made of the experimental and theoretical photon relative transition intensities and reasonable agreement is obtained for the case: K 1 = 1 2 , b E1 =0 . The properties of this band are consistent with those expected for Nilsson state 1 2 − [501]. Estimates of the log ft values of Np239 beta decay to levels of the new band are made and are discussed in terms of the states involved.

In order to assist experimental assignments in olefinic and aromatic fluorine compounds, fluorine nuclear coupling constants have been obtained from the first-order self-consistent perturbation theory equation with the INDO molecular orbital approximation in a series of fluoro-substituted furans. There is a clear distinction between the magnitudes and signs for the four fluorine coupling positions; the importance of the orbital and spin-dipolar contributions is very clear. Tentative signs are suggested for all the coupling constants.

Koopmans' theorem ionization potentials from ab initio gaussian basis set calculations on cis, trans and skew forms of HOOH and HSSH are compared with experimental values from photoelectron spectroscopy.

Ab initio calculations with a double zeta contracted gaussian basis are used to discuss the ionization potentials of o-, m- and p-difluorobenzene, and the correlation with benzene. Interpretations of the experimental X-ray and UV photoelectron spectra are given.

Ionization potentials calculated by the valency electron self-consistent molecular method CNDO/2 for BF 3 , HCHO, O 3 , N 2 , CO, the fluoromethanes, and some fluorobenzenes are compared with experimental values obtained by photo-electron and ultraviolet spectroscopy.

Values of vicinal fluorine nuclear coupling constants for the stable rotamers of (CH2F)2, CHF2, CH2F, (CHF2)2 and CF3. CH2F are obtained from the first-order self-consistent perturbation theory equation with the INDO molecular orbital approximations. A clear distinction is found between gauche and trans values. A comparison with experimental values for similar compounds is made.

During the course of an outbreak of meningococcal septicaemia, detailed coagulation studies were carried out on two patients with fulminating infections in which there were massive purpuric reactions and associated renal failure. N. meningitidis , serotype C, was isolated from both patients. In these patients there were severe thrombocytopenia, procoagulant depletion and abnormally high fibrinogen levels. In the second case heparin was started after the first coagulation studies were made and was continued until death 20hr. later. Autopsy findings on this patient suggested a generalized Schwartzmann reaction. It is considered that death in both patients was due to an explosive intravascular coagulation process for which anticoagulant therapy, in the second case, was too late to be effective. In the presence of an acute, and apparently irreversible 'thrombophilic' shift in the coagulation mechanisms, it is suggested that a good case can be made for an active programme of thrombolytic therapy as a primary line of attack.