Determination of theCs20g−(P3/2)potential curve and ofCs6P1/2,3/2atomic radiative lifetimes from photoassociation spectroscopy

An analytical expression for the external well of the ${\mathrm{Cs}}_2{0}_g^{-}{(6s+6P}_{3/2})$ double-well potential curve is derived, involving asymptotic parameters fitted on the spectrum obtained from photoassociation of ultracold cesium atoms and ultracold molecule formation [Fioretti et al., Europhys. J. D 5, 389 (1999)]. The results are compared to a previous Rydberg-Klein-Rees determination from our group, and may have consequences on the determination of cesium triplet scattering length. Values for radiative lifetimes ${\tau }_{3/2}=30.462\mathrm{}\left(3\right)\mathrm{}$ ns and ${\tau }_{1/2}=34.88\mathrm{}\left(2\right)\mathrm{}$ ns of the ${6P}_{3/2}$ and ${6P}_{1/2}$ atomic levels, respectively, are extracted with an accuracy better than previous determinations. The method of Derevianko and Porsev [Phys. Rev. A 65, 053403 (2002)], allows the derivation of an improved value for the van der Waals coefficient of ground-state cesium molecule, $C_6^{6s}=6828\mathrm{}\left(19\right)\mathrm{}$ a.u.