Radiative transitions in quasi-molecules

Abstract

Radiative transitions occurring at atomic collisions are considered. Attention is focused on the transitions that are either impossible in individual atoms or ions or forbidden by the selection rules. The excitation of continuous-spectrum electron states is considered for the first time by an example of photodetachment at collisions of negative ions with neutral atoms.

Asymptotically spin forbidden quasimolecular radiative transitions (review)

“…Pay attention to the fact that the dipole moment of the optical transition changes sign, i. e., changes orientation to the opposite, approximately at the boundary of the region of dominance of long-range or exchange forces. Here the situation also resembles the vanishing of the dipole moment known in the physics of the atomic photoelectric effect [60,61], but at a certain absorption frequency. The presence of zeros of the dipole moment depending on the distance between nuclei with charges Z 1,2 was also established in the exact calculation of the moments in the one-electron problem [62].…”

“…Using the semiclassical approximation for the trajectory of atoms allows us to write a simple formula for the shape of the spectrum. It turns out [73] that, as in the case of an isolated atom, it is sufficient to calculate the Fourier component of the matrix element of the dipole moment D, but which is now calculated on the time-dependent wave functions of the quasimolecule. For example, the amplitude of photon emission has the form b…”

Bound-free transitions in H + H – collisions

“…Although the quasimolecular matrix elements increase with increasing R it does not lead to difficulties at large R. In this case quasimolecular potential energies of both states involved U u = U g , and it is obligatory to use the sum of amplitudes of two different ways of detachment [4]. Thus, the quasimolecular oscillator strength reduces to the oscillator strength for a single atomic ion at large distances.…”