Hyperfine structure of Cs$_2$ and RbCs excited molecules

Unlike ground state alkali-metal diatomics, very little is known about the hyperfine structure of excited electronic states. We present a preliminary analysis of the expected structure of the rovibrational levels of the Cs$_2$ and RbCs excited electronic states correlated to the lowest $^2$S+$^2$P limit based on an asymptotic model for the hyperfine Hamiltonian [1]. We set up potential curves built on long-range atom-atom interaction connected to short-range ab-initio results obtained in our group. The hyperfine structure strongly depends on the projection of the total angular momentum of the molecule, and on the sum of projections of the total angular momentum of the separated atoms. The comparison with the experimental data recorded in Innsbruck [2] will be presented. The possible interaction of electronic states at short distances due to hyperfine coupling is discussed.\\[4pt] [1] D. Comparat, et al, Eur. Phys. J. D 11, 59 (2000)\\[0pt] [2] J. G. Danzl et al Faraday Disc. 142, 283 (2009)