Photoionization of the francium [7P.sub.3/2] state

We have measured the non-resonant photoionization cross section of the [7P.sub.3/2] state of francium for 442 nm light to be 20.8 [+ or -] 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. Key words: photoionization, alkali atoms, magneto-optical trap. Nous mesurons que la section efficace de photo-ionisation hors resonance de l'etat [7P.sub.3/2]] du francium pour une lumiere de 442 nm est de 20.8 [+ or -] 7.11 Mb. Les atomes sont irradies dans un piege magneto-optique et nous deduisons le taux de photo-ionisation a partir du changement du temps de vie du piege. Le resultat est coherent avec la simple extrapolation de sections efficaces connues pour d'autres atomes alcalins. [Traduit par la Redaction] Mots-cles: photo-ionisation, atome alcalin, piege magneto-optique, francium, etat excite.
1. Introduction The near-threshold photoionization of atoms is an important process to consider as a loss mechanism in two-species magnetooptical traps (MOTs) [1]. It is also of indirect importance in [...]