SUB-DOPPLER LASER SPECTROSCOPY OF THE NAK MOLECULE

Excitation of NaK molecules in a collimated molecular beam by a single mode tunable argon laser with sub-Doppler resolution allows selective population of definite vibrational rotational levels (ν′, J′) in the D 1Π-state. The resultant fluorescence consists of a singlet spectrum in the 470-570 nm range and a triplet spectrum in the 625-715 nm range. The analysis of the triplet fluorescence, which consists of discrete lines and of a modulated continuum, allows the determination of the a 3∑ + potential and yields very precise values for the dissociation energies in the a 3∑+ and X 1∑ + states, which are measured as De(3∑ +) = 204±4 cm-1 and De( 1∑+) = 5269±6 cm-1. For some excitation wavelengths a fluorescence spectrum with discrete lines and with a double-modulated continuum is observed which is assigned to Condon internal diffraction" bands terminating close below and above the dissociation limit of the X 1∑+ state. Its relevance for the determination of the upper and lower potential curves is discussed. © 1979 American Institute of Physics."