The 530 nm system of KRb observed in a pulsed molecular beam: New electricquadrupole transitions (1 (1)Delta-X (1)Sigma(+))

New electronic transitions of KRb are identified near 530 nm by resonance e nhanced two photon ionization study in a supersonic molecular beam. The rot ational structure shows O, P, Q, R, and S branches. From the high resolutio n rotational analysis and comparison with the spectra of other alkali diato mic molecules we assign the observed bands to the 1 (1)Delta -X (1)Sigma () transitions of KRb, which are allowed by electric quadrupole radiation. W e obtain molecular constants for the upper electronic state of (KRb)-K-39-R b-85 as omega (e)=64.624 1(35)cm(-1), T-e=18 991.011 0(14)cm(-1), B-e(')=0. 035 703 9(10)cm(-1), and R-e=4.204 55(6) A. Another new electronic transiti on observed in the same wavelength region is assigned to the 3 (3)Sigma (+) -X (1)Sigma (+) transition from the comparison with ab initio calculations. (C) 2001 American Institute of Physics.