Polarization and hyperfine transitions of metastableXe129in discharge cells

Abstract

The polarization and relaxation rates of metastable 129 Xe atoms are measured with magnetic resonance spectroscopy, at both microwave frequencies, where F = 1 transitions are induced between the sublevels, and at radiofrequencies, corresponding to F = 0 transitions. The nuclear spin polarization of the resonant velocity group is measured to be 22 ± 2%. The relaxation of metastable xenon atoms is dominated by depolarizing collisions with ground-state atoms, with lesser contributions from metastability exchange collisions.

Fundamentals of metastability exchange optical pumping in helium

“…For any transition addressing a single Zeeman sublevel of the 2 3 S state, the PE does not depend on nuclear polarisation nor on OP intensity. This occurs for the C 8 line of 3 He and the D 0 line of 4 He at low field, and also for several high-field transitions. For the D 0 line, the PE additionally does not depend on pressure.…”

“…Equations similar to Eqs. 11 and 12 are given in [24] for the populations of 4 He atoms involved in MEOP of isotopic mixtures.…”

“…However both the nuclear polarisation I m and the density n m of atoms in the metastable state can strongly vary over the volume of the cell, hence Eq. 17 involves a spatial average over the cell 4 where the field-dependent parameters L ± =cos 2 θ ± − sin 2 θ ± can be evaluated from the 2 3 S state mixing parameters θ − and θ + [24], the nuclear polarisation I m in the metastable state is directly derived from the computed populations. For B=0, the coefficients are L ± =±1/3.…”

“…Metastability exchange optical pumping (MEOP), discovered in 1963 [1], exclusively applies to 3 He as demonstrated by various attempts for other gases [2,3,4], while spin-exchange OP (that involves an alkali vapour [5,6,7]) can be used to efficiently polarise 129 Xe as well. MEOP is actually performed between two excited states of helium (Fig.…”

“…This model has been also used to discuss OP experiments with a broadband laser [20,21]. Extensions to specific situations have been proposed, but not fully developed, for OP in 3 He- 4 He isotopic mixtures 1 [23] and for OP in high magnetic fields [12,13,24]. Recently, we have developed a more comprehensive model of MEOP.…”