T. K. Rai Dastidar

Dissociative Recombination of H 2 + , HD + and D 2 + Molecular Ions

An ab initio calculation of the cross-sections of dissociative recombination (DR) in H + 2 , HD + and D + 2 has been made using the projection operator technique. A single-configuration molecular orbital wavefunction has been used for the molecular resonance state, although the applicability of such a simple wavefunction has not been fully tested. The decay width has been calculated in the “local” approximation. Comparison with experiment shows that for H + 2 the calculated results can fully account for the total DR cross-section in the low and intermediate energy regions, and that the local approximation is sufficiently accurate to account for the undulatory structure in the energy dependence of the DR cross-section. A similar structure is also obtained for D + 2 , although here the agreement with experiment is less marked. For HD + no particular heteronuclearity effect is observed.

Force Constants of N2O4 and NO2 and the Viscosity of the Dissociating System N2O4⇌2NO2

By analyzing the experimental viscosity of the dissociating system N2O4⇌2NO2, the force constants of N2O4 and NO2 have been obtained for the Lennard‐Jones (12:6) potential. The calculations made with the force constants thus obtained suggest that, in agreement with theory, chemical reaction has no significant effect on the viscosity of a chemically reacting gas mixture.

Use of an approximate diabatic molecular representation in He+ -He charge transfer collision

Abstract A single-configuration “frozen-orbital” molecular basis set has been used as an approximation to the “standard” radial diabatic representation defined by Smith. The usefulness of this approximate representation has been demonstrated in an eight-state close-coupled treatment of the He+ -He resonant transfer collisions in the impact parameter approximation. Apart from the Σ-Σ potential couplings the two Σ-Π rotational couplings at short range have been considered. Generally satisfactory agreement with the experimental data of Nagy ., together with a significant improvement in the estimate of the rotational coupling effects toward the region of large EO (≳ 3-4 keV deg) as compared to the earlier theoretical work of McCarroll and Piacentini is obtained.

LOCAL GAUGE INVARIANCE OF RELATIVISTIC QUANTUM MECHANICS AND CLASSICAL RELATIVISTIC FIELDS

We extend our earlier work1 to demonstrate that all free matter fields (Bose as well as Fermi, massive as well as massless), that transform like Φ→TΦ under a local Abelian gauge transformation T=exp(–iβ) with β an arbitrary function of space and time, are governed by field equations that are invariant under such local gauge transformations.

A POSSIBLE ANISOTROPY IN BLACK BODY RADIATION VIEWED THROUGH NON-UNIFORM GASEOUS MATTER

A nonlocal gauge symmetry of a complex scalar field, which can be trivially extended to spinor fields, was demonstrated in a recent paper (Mod. Phys. Lett.A13, 1265 (1998), hep-th/9902020). The corresponding covariant Lagrangian density yielded a new, nonlocal quantum electrodynamics. In this letter we show that as a consequence of this new QED, a black body radiation viewed through gaseous matter appears to show a slight deviation from the Planck formula, and propose an experimental test to check this effect. We also show that a non-uniformity in this gaseous matter distribution leads to an (apparent) spatial anisotropy of the black body radiation.

Use of a diabatic molecular expansion in studies on electron capture by He2+ ions in helium at keV energies

In this preliminary work, using a 3-state diabatic molecular expansion without any excited channels, we have studied within the semiclassical impact parameter approximation the single charge transfer process He2++He(1s2)→He+(1s)+He+(1s). Our results agree very well with experiment, which demonstrates the usefulness of this type of diabatic molecular basis in doubly charged ion-atom collision systems.

Gauge Invariance in non-relativistic quantum mechanics

SummaryWe show that non-relativistic quantum mechanics is invariant under a local gauge transformation even in the absence of any external electromagnetic field, provided we do not exclude the arbitrary phase factor in the coordinate representation of the wave vector. A generalised, gauge-invariant form of the Schroedinger equation, as well as gauge-invariant canonical momentum and Hamiltonian operators are introduced. In the presence of an electromagnetic field, the new Hamiltonian operator turns out to be identical with the «energy operator» introduced by K. H. Yang. A previously derived result, proving thenon-equivalence of the minimal-coupling and the multipolar forms of matter-radiation interaction, is shown to follow as a corollary.

Angular distribution of product ions in the ion‐molecule reaction H+2(He,H) HeH+ by quantum mechanical impulse approximation

Quantum mechanical impulse approximative is used to obtain the angular distribution of product ions for the reaction H2++He→HeH++H.(AIP)

On the mechanism of the ion-molecule reaction CH3+ + CH4 = C2H5+ + H2

Abstract Experimental evidence supporting the “direct” reaction model and the “intermediate complex” model for the reaction CH 3 + (CH 4 , H 2 )C 2 H 5 + are analysed. It is shown that the evidence for the former can equally well be interpreted in terms of a proposed model of persistent complex formation and decay. The plausibility of a “direct” mechanism is discussed and is found to be poor.

Identification of single charge transfer channels in –N2 collisions by translational energy spectroscopy

Single charge transfer reactions in the collision of ions at a laboratory energy of 2 keV with N2 were observed using translational energy spectroscopy (TES). Within the limitation of the energy analyser resolution (∼ 8/q eV, q being the ionic charge number), the translational energy spectrum shows a single broad charge transfer peak with a rich substructure. The latter looks like a conglomeration of closely spaced channels clumped together, corresponding mainly to charge transfer into excited states, rather than into the ground state. The reaction channel assignments were made using data available in the literature. Our findings are in accord with a recent experimental result, but there are no theoretical calculations to compare our experimental measurements with.