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Physical Review A

Disalignment transitions in cold collisions of 3P atoms with structureless targets in a magnetic field

Roman V. Krems, A. Dalgarno

Published Jul 11, 2003• 36 citations
Publisher

Abstract

A method for quantum-mechanical calculations of cross sections for the Zeeman transitions in collisions of ${}^{3}P$ atoms with structureless targets in a magnetic field is presented and applied to the study of magnetic and electronic relaxation in oxygen-helium and carbon-helium collisions at cold and ultracold temperatures. The rate constants for collisionally induced transitions between Zeeman levels in ground-state oxygen have large magnitudes in a 1 T field. It is shown that magnetic fields induce the forbidden ${}^{3}{P}_{1}$ $\ensuremath{\rightarrow}$ ${}^{3}{P}_{0}$ transition in ultracold collisions of carbon with helium. The cross section vanishes at zero energy for field-free collisions, but becomes infinitely large in a finite magnetic field, varying with velocity $v$ and magnetic field B as ${B}^{2}/v.$

DOI
10.1103/physreva.68.013406

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Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: An ab initio study of He + CH2(X~){\rm CH}_2(\tilde{X})CH2​(X~) CH 2(X) collisions
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The dynamics of the elastic and inelastic scattering of helium atoms in collisions with oxygen atoms in different fine-structure levels O(3Pj)\mathrm{O}{(}^{3}{P}_{j})O(3Pj​) at cold and ultracold temperatures is investigated using two sets of interaction potentials of the molecule HeO in the ground \ensuremath{\Sigma} and \ensuremath{\Pi} states. Scattering resonances occur in the collisions at low energies. The positions and shapes of the resonance peaks in the inelastic channels do not always mirror those in the elastic channels. The real parts of the scattering lengths are all positive with values in the range 2.5--4.2 \AA{}. The rate coefficients for the quenching of the 3P0{}^{3}{P}_{0}3P0​ and 3P1{}^{3}{P}_{1}3P1​ fine-structure levels decrease almost by one order of magnitude as the temperature decreases from 1 to 0 K and their zero temperature values are, respectively, $3.09\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ and $3.27\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{3}{\mathrm{sec}}^{\ensuremath{-}1}.$
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