Spectroscopy of 39K85Rb triplet excited states using ultracold a 3Σ+ state molecules formed by photoassociation

Convenient state-selective detection methods are proposed for exploring triplet Rydberg states from the metastable a (3)Sigma(+) state of ultracold KRb molecules by resonance-enhanced two-photon ionization and time-of-flight (TOF) mass spectroscopy. This would allow the first accurate determination of the ionization potential. Particularly suitable resonant intermediate states include the 2 (3)Pi(Omega), 3 (3)Sigma(+) and 4 (3)Sigma(+) states, and we report spectroscopic studies of these states. For the 2 (3)Pi(Omega) state, the spin-orbit components (Omega = 0(+), 0(-), 1 and 2) have been investigated and a shallow long-range state (5(0(+))) at similar to 9.3 angstrom has been observed. We compare our observations of these three states with predictions based on ab initio potential energy curves. Such studies may also permit the direct observation of autoionizing resonances leading to efficient formation of low-lying rovibrational levels of the (2)Sigma(+) ground state of KRb+, ideally in the upsilon(+) = 0, N+ = 0 level.