Experimental Study of the B¹Π state of NaK Dimers and Lifetime Measurements Using High-Resolution Time-Resolved Laser Induced Fluorescence Spectroscopy

We present an experimental study of the B¹Π(Na(3s)+K(4p)) state of NaK heteronuclear molecules and the radiative lifetime masurements using a time-resolved laser-induced fluorescence (LIF) spectroscopy. Selective excitation from the thermally populated levels in the ground X¹Σ state to the excited B¹Π (v'=6, J'=35) state was achieved using a tunable dye laser, pumped by the 5-ns pulsed Nd:YAG laser. More than 26 rovibrational structures of molecular fluorescence from the excited state were collected within the 11000-20000 cm^-1 range by using a high-resolution imaging spectrometer. The spectrum was then analyzed and compared with the Franck–Condon factors, calculated using the Fortran LEVEL 8.0 program. The excited-state lifetime was then measured using a photon-counting technique at various pressures. Radiative lifetimes were determined using Stern-Volmer analysis and the results were compared with the theoretical calculations performed by the Seth Ashman group at Providence College.