Suppression of Penning ionization by orbital angular momentum conservation

TL;DR

This paper demonstrates that conservation of orbital angular momentum projection, in addition to electron spin, can suppress Penning ionization in metastable helium and lithium collisions, aiding quantum degeneracy efforts.

Contribution

It reveals that orbital angular momentum projection is conserved during Penning ionization, providing a new method to control reaction processes in cold atomic collisions.

Findings

Suppression of Penning ionization in He-Li collisions.

Orbital angular momentum projection is conserved during ionization.

Potential for improved laser cooling and trapping schemes.

Abstract

The efficient suppression of Penning-ionizing collisions is a stringent requirement to achieve quantum degeneracy in metastable rare gases. Thus far, such loss processes have been avoided by electron-spin polarizing the collision partners. Here, we report on the efficient suppression of Penning ionization in collisions between metastable He and laser-excited Li atoms. The results illustrate that not only the electron spin, but also $\Lambda$ - the projection of the total molecular orbital angular momentum along the internuclear axis - is conserved during the ionization process. Our findings suggest that $\Lambda$ conservation can be used as a more general means of reaction control, for example, to improve schemes for the simultaneous laser cooling and trapping of metastable He and alkali atoms.