Spectroscopic investigation of the A and 3 1Σ+ states of 39K85Rb

By using a combination of molecular beam (MB) excitation spectra and two distinct ultracold molecule excitation spectra (UM+ and UM-), we have assigned high vibrational levels of the A and 3 (1)Sigma(+) states from absorption spectra of the mutually strongly perturbed A (1)Sigma(+) - 3 (1)Sigma(+) - 1 (1)Pi - 2 (3)Sigma(+) - b (3)Pi states of ultracold (KRb)-K-39-Rb-85 molecules in the energy region between 15116 and 16 225 cm(-1) above the minimum of the ground X (1)Sigma(+) state. The ultracold molecules (UM+ and UM-) are formed by radiative decay following photoassociation (PA) to a specific level of the 3(0(+)) state (UM+) or to a specific level of the 3(0(-)) state (UM-). We observe that the A and 3 (1)Sigma(+) states are observable in the UM+ spectra, but absent from the UM-spectra. This is explained by considering Hund's case (c) selection rules and transition dipole moments between the upper excited A (1)Sigma(+) (2(0(+))) state and the three Omega components (0(+), 0(-), and 1) at the ground-state dissociation limit. We propose further investigations of the extended potential wells of the A and 3 (1)Sigma(+) states by combining short-range MB excitation spectra in a narrow Franck-Condon (FC) window near R-e of the X (1)Sigma(+) state, and long-range UM (and PA) excitation spectra, which have much larger FC windows. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4771661]