Volume 17, Issue 4
October 1981, pages 297-368
pp 297-308 October 1981 Solid State Physics
Electrical conductivity and stimulated thermocurrent (stc) studies are carried out in dicalcium lead propionate (dlp) in pure, Cu2+, Fe3+ and acetate doped single crystals over a temperature range of 303° to 503° K. Conductivity measurements on pure and doped single crystals ofdlp indicate that both propionate anions and metallic cations are responsible for the transition occurring at 333°K. Thermoelectric power measurements from 340° to 500°K indlp (pure) indicate that the transport charge carriers are electrons. A model for the conduction mechanism is proposed on the basis of hopping ofπ or resonating electrons of carboxyl groups through tunnel paths involving metal ions (Pb2+ and Ca2+). From activation energies estimated from conductivity andstc measurements, thestc peak indlp (Fe3+) occurring at 513°K is attributed to impurity vacancy jump mechanism.
pp 309-314 October 1981 Atomic And Molecular Physics
The differential cross-sections forē-helium elastic scattering are calculated by using Yateshigh-energy higher order Born approximations, through 0 (KiEmphasis>−2) of the incident electron momentum, and comparisons have been made with the recent theoretical and experimental results.
pp 315-326 October 1981 Atomic And Molecular Physics
The three dominant mechanisms giving major contributions to vibrational relaxation in molecular systems are (a) pure dephasing, (b) depopulation (or energy relaxation), and (c) resonant transfer. Here (c) is not considered but the effects due to thesimultaneous occurrence of (a) and (b) are treated within a stochastic model. In dealing with (a), the vibrational frequency is assumed to undergo random uncorrelated ‘jump’, due to fluctuations in the environment of the active molecule between a continuous set of values. The ensuing results are somewhat different from those of the commonly used Kubo model of vibrational dephasing, especially at long times and appear to be better suited in interpreting certain experimental data. The model is next extended to include the simultaneous occurrence of (b). The calculation leads to two important conclusions: (i) the lineshape is not just the convolution of those due to (a) and (b), and (ii) the lineshape is asymmetric, if the intermolecular interactions are not isotropic.
pp 327-335 October 1981 Crystallography
It is suggested that the radio astronomical technique of image reconstruction calledclean could be profitably used in crystallography to improve sharpened Patterson maps andE-maps. The method is here generalized to handle the symmetries which arise in crystallographic maps. Simulations on model one and two dimensional structure are presented to illustrate the power of the method.
pp 337-352 October 1981 Nuclear And Particle Physics
The state of polarization of the recoil nucleus inγ+3He→π°+3He as well as the asymmetry in the differential cross-section when the initial3He is polarized are studied together with the differential cross-section taking into consideration theS, S′ andD-state admixtures in the nuclear wavefunctions. In view of the considerable spin dependence in the photoproduction amplitudes these observables are found to be quite sensitive to the small admixtures ofS′ andD-states in the nuclear wave-functions.
pp 353-360 October 1981 Nuclear And Particle Physics
Existing data on the differential cross-section ratio at high energies for pp,$$\bar p$$p, π±p andK±p scatering have been fitted by the proposed convergent polynomial expansion to determine the unknown coefficients in the scaling function. It is found that the data are very well represented within and somewhat outside the peak regions by only four or five terms in the proposed series in terms of Laguerre polynomials.
pp 361-368 October 1981 Chemical Physics
Ising model formalism developed for order-disorder transition in poly-peptides has been modified for the study of order-order transition in a macromolecular system. A two-state theory is developed and applied to poly-L-proline I and II. Various transition curves for different chain lengths are obtained as a function of solvent composition. Transition curves and crossing point for a solvent system are in excellent agreement with the experimental data on poly-L-proline.
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