Use of a diode laser to measure the spin polarization of an optically-pumped ensemble of He(2{sup 3}S) atoms

A polarized He{sup +} ion source based on spin conservation in Penning ionization reactions involving polarized He(2{sup 3}S) atoms contained in an optically-pumped, rf-excited helium discharge is being developed for surface studies. To optimize source performance, the He(2{sup 3}S) polarization must be determined. The authors have devised a technique for doing this that involves measuring the attenuation of a circularly-polarized probe beam provided by a 1.083 {mu}m DBR diode laser whose output frequency is scanned by varying the drive current to allow separate measurements on the 2{sup 3}S{sub 1}-2{sup 3}P{sub 0}, 2{sup 3}P{sub 1} and 2{sup 3}P{sub 2} transitions. As will be discussed, several independent expressions for the polarization (and alignment) can be derived from the experimental data thus providing valuable internal consistency checks. The technique is simple to implement and reliable in operation.