Spin-dipole-induced lifetime of the least-bound 5Σ+g state of He(23S1)+He(23S1)

Abstract

The properties of the least-bound vibrational level (v=14) of the Σg+5 state formed during the ultracold collision of two spin-polarized metastable 2S13 helium atoms are crucial to studies of photoassociation spectroscopy of metastable helium. We report a calculation of the autoionization lifetime τg of this state induced by spin-dipole coupling of the Σg+5 state to the Σg+1 state from which Penning and associative ionization processes are highly probable. We find τg≈150μs , significantly larger than the recent experimental estimates of (0.5‑3)μs.