Photoionization of the francium 7P_3/2 state

Abstract

We have measured the non-resonant photoionization cross section of the 7P3/2 state of francium for 442 nm light to be 20.8 ± 7.1 Mb. Atoms were irradiated in a magneto-optical trap, and we deduce the photoionization rate from the change in trap lifetime. The result is consistent with a simple extrapolation of known cross sections for other alkali atoms.

Studies of the weak interaction in atomic systems: towards measurements of atomic parity non-conservation in francium

“…In addition, as an atom excited to 8s cascades down via the 7p 3/2 state, it can get photo-ionized by 506 nm light (the equivalent process cannot occur in Cs). We have measured the cross section for this process [59]. As pointed out by Vieira and Wieman [60], lowering the applied electric field (leading to a reduced 7s-8s excitation rate, but increasing the parity flip asymmetry, with a practical lower limit of 120 V cm −1 in Fr, where the Stark-induced and M1 amplitudes become equal), and reducing the intensity of the 506 nm light can address this problem.…”