Theory of nuclear spin conversion in ethylene

First theoretical analysis of the nuclear spin conversion in ethylene molecules (13^CCH4) has been performed. The conversion rate was found equal approx. 3x10^{-4} 1/s*Torr, which is in qualitative agreement with the recently obtained experimental value. It was shown that the ortho-para mixing in 13^CCH4 is dominated by the spin-rotation coupling. Mixing of only two pairs of ortho-para levels were found to contribute significantly to the spin conversion.Comment: 20 pages, 5 eps figure

Consistent Treatment of Relativistic Effects in Electrodisintegration of the Deuteron

The influence of relativistic contributions to deuteron electrodisintegration is systematically studied in various kinematic regions of energy and momentum transfer. As theoretical framework the equation-of-motion and the unitarily equivalent S-matrix approaches are used. In a (p/M)-expansion, all leading order relativistic $\pi$-exchange contributions consistent with the Bonn OBEPQ model are included. In addition, static heavy meson exchange currents including boost terms, $\gamma\pi\rho/\omega$-currents, and $\Delta$-isobar contributions are considered. Sizeable effects from the various relativistic two-body contributions, mainly from $\pi$-exchange, have been found in inclusive form factors and exclusive structure functions for a variety of kinematic regions.Comment: 41 pages revtex including 15 postscript figure

Covariant description of inelastic electron--deuteron scattering:predictions of the relativistic impulse approximation

Using the covariant spectator theory and the transversity formalism, the unpolarized, coincidence cross section for deuteron electrodisintegration, $d(e,e'p)n$, is studied. The relativistic kinematics are reviewed, and simple theoretical formulae for the relativistic impulse approximation (RIA) are derived and discussed. Numerical predictions for the scattering in the high $Q^2$ region obtained from the RIA and five other approximations are presented and compared. We conclude that measurements of the unpolarized coincidence cross section and the asymmetry $A_\phi$, to an accuracy that will distinguish between different theoretical models, is feasible over most of the wide kinematic range accessible at Jefferson Lab.Comment: 54 pages and 24 figure

Excimer emission in Indium Vapour

An excimer band extending between 271 and 284 nm in indium vapor is reported which is the result of a two-photon resonant ionization of indium vapor excited by a dye laser tuned to the 6 2S1/2-5 2P1/2 atomic transition. The observations were made both in quartz cells and in a heat pipe oven at temperatures between 943 and 1223 K in the presence of He, Ne and Ar buffer gases. The excimer state giving rise to the emission occurs at an energy which can be correlated with the In(7 2S1/2) and In(5 2P1/2) separated atom states. No structure other than a degradation to the blue is apparent in the spectrum

HgIn photoassociation, bound-bound transitions, and excimer emission.

Laser excitation of In atoms at the 6 2S1/2–5 2P1/2 atomic resonance transition wavelength of 410.3 nm in the presence of Hg vapor produces several types of emission features: HgIn excimer satellites on the red wings of the In resonance fluorescence transitions at 410.3 and 451.1 nm, bound-bound HgIn molecular fluorescence at 499 and 522 nm resulting from photoassociation of In(6 2S1/2) with Hg(6 1S0), and UV atomic fluorescence from the In(5 2D) states that lie at energies above the In(6 2S1/2–5 2P1/2) excitation. These various spectral features are interpreted in terms of a proposed HgIn potential-energy level diagram with additional information from measured excited-state lifetimes and the power dependence of the laser excitation at 410.3 and 522 nm. Direct excitation of the 499 and 522 nm HgIn bound-bound transitions also produces emission at 410.3 and 451.1 nm resulting from collisional dissociation of the excited HgIn states