Absolute polarization measurements and natural lifetime in the 7 S 1/2 state of Cs

Abstract

We report Hanle effect measurements of the relaxation in the 7 S1/2 state of cesium by collisions with cesium or buffer gas (helium) atoms in an electric field. The results show the relaxation of the spin polarization to remain isotropic in the adopted configuration, and justify the calibration procedure used in our recent measurements of parity violation in the 6 S-7 S transition of cesium. We also obtain the lifetime of the 7 S1/2 state : τ7 S = 48.5 ± 0.5 ns (and the depolarization cross-section σCsHe = (1.10 ± 0.05) x 10-15 cm2). Accordingly the semi-empirical value of the scalar polarizability of the 6 S-7 S transition becomes α = - (265.1 ± 2.5) a30