Recent experiments using polarized electron beams have shown that spin exchange effects for elastic collisions with ${\mathrm{O}}_{2}$ and NO are much smaller than for Na atoms. We report calculated spin-flip differential cross sections for elastic collisions of polarized electrons with ${\mathrm{O}}_{2}$ in agreement with experiment. In general, we can attribute the large variation of the spin-flip differential cross sections to resonances and interference effects. Such features arising from interference, however, may be washed out in the molecular case due to the average over orientations. Calculations with oriented ${\mathrm{O}}_{2}$ molecules show strong exchange effects as for Na.Recent experiments using polarized electron beams have shown that spin exchange effects for elastic collisions with ${\mathrm{O}}_{2}$ and NO are much smaller than for Na atoms. We report calculated spin-flip differential cross sections for elastic collisions of polarized electrons with ${\mathrm{O}}_{2}$ in agreement with experiment. In general, we can attribute the large variation of the spin-flip differential cross sections to resonances and interference effects. Such features arising from interference, however, may be washed out in the molecular case due to the average over orientations. Calculations with oriented ${\mathrm{O}}_{2}$ molecules show strong exchange effects as for Na.

Physical Review LettersMar 16, 199231 citations

Hyperfine and Zeeman interactions in ultracold collisions of molecular hydrogen with atomic lithium

Hubert Jóźwiak, Timur V. Tscherbul, Piotr Wcisło

We present a rigorous quantum scattering study of the effects of hyperfine and Zeeman interactions on cold Li-H2 collisions in the presence of an external magnetic field using a recent ab initio potential energy surface. We find that the low-field-seeking states of H2 predominantly undergo elastic collisions: the ratio of elastic-to-inelastic cross sections exceeds 100 for collision energies below 100 mK. Furthermore, we demonstrate that most inelastic collisions conserve the space-fixed projection of the nuclear spin. We show that the anisotropic hyperfine interaction between the nuclear spin of H2 and the electron spin of Li can have a significant effect on inelastic scattering in the ultracold regime, as it mediates two processes: the electron spin relaxation in lithium and the nuclear spin-electron spin exchange. Given the predominance of elastic collisions and the propensity of inelastic collisions to retain H2 in its low-field-seeking states, our results open up the possibility of sympathetic cooling of molecular hydrogen by atomic lithium, paving the way for future exploration of ultracold collisions and high-precision spectroscopy of H2 molecules.We present a rigorous quantum scattering study of the effects of hyperfine and Zeeman interactions on cold Li-H2 collisions in the presence of an external magnetic field using a recent ab initio potential energy surface. We find that the low-field-seeking states of H2 predominantly undergo elastic collisions: the ratio of elastic-to-inelastic cross sections exceeds 100 for collision energies below 100 mK. Furthermore, we demonstrate that most inelastic collisions conserve the space-fixed projection of the nuclear spin. We show that the anisotropic hyperfine interaction between the nuclear spin of H2 and the electron spin of Li can have a significant effect on inelastic scattering in the ultracold regime, as it mediates two processes: the electron spin relaxation in lithium and the nuclear spin-electron spin exchange. Given the predominance of elastic collisions and the propensity of inelastic collisions to retain H2 in its low-field-seeking states, our results open up the possibility of sympathetic cooling of molecular hydrogen by atomic lithium, paving the way for future exploration of ultracold collisions and high-precision spectroscopy of H2 molecules.

arXiv:2312.13652The Journal of Chemical PhysicsMar 5, 20242 citations

The Role of Electron Spin in Atomic Collisions

Wolfgang Jitschin

NATO ASI series. Series B : PhysicsJan 1, 19850 citations

Recent experiments using polarized electron beams have shown that spin exchange effects for elastic collisions with

{\mathrm{O}}_{2}

and NO are much smaller than for Na atoms. We report calculated spin-flip differential cross sections for elastic collisions of polarized electrons with

{\mathrm{O}}_{2}

in agreement with experiment. In general, we can attribute the large variation of the spin-flip differential cross sections to resonances and interference effects. Such features arising from interference, however, may be washed out in the molecular case due to the average over orientations. Calculations with oriented

{\mathrm{O}}_{2}

molecules show strong exchange effects as for Na.