Electron spin exchange with O2: Effects on the muon spin rotation, the electron spin resonance, and the positronium lifetime.

Abstract

Electron spin exchange with spin one paramagnetic species has been investigated with particular emphasis on the cases of hydrogen (H={ital p}{sup +}{ital e}{sup {minus}}), Mu (Mu={mu}{sup +}{ital e}{sup {minus}}), positronium (Ps={ital e}{sup +}{ital e}{sup {minus}}) colliding with O{sub 2}. The effects of spin exchange on electron spin relaxation (ESR), muon spin relaxation ({mu}SR), and positronium lifetime measurements are described in terms of the difference in phase shifts between quartet and doublet encounters ({Delta}), which will allow one to interpret ESR, {mu}SR, and positron data in a unified way and help one to understand isotope mass effects not only in spin exchange but also in chemical reactions, which often compete with spin exchange. For instance, the ESR and {mu}SR relaxation rates in high transverse fields are expressed, in terms of the rate of collisions {lambda}, as {lambda}{sup {ital e}}{sub {ital T}}=(32/27){lambda} sin{sup 2}({Delta}/2) and {lambda}{sub {ital T}}{sup {mu}}=(16/27){lambda} sin{sup 2}({Delta}/2), respectively, and the so-called statistical factors, such as (32/27) and (16/27), are strong functions of the magnitude and direction of the applied field.