Observations on the B1Π state of the NaK molecule

Abstract

The lowest 1Π state of the NaK molecule, B(1) 1Π, which dissociates to Na (2S1/2) + K (2P3/2), has been studied in three ways: (i) by laser-induced fluorescence recorded at high resolution by Fourier-transform spectrometry, (ii) by dye-laser excitation spectroscopy, and (iii) by observations of the effect of an electric field, which mixes the e and f parity levels of the B1Π state. The B state is subject to numerous small perturbations, many of which arise from interactions with a triplet state, c3Σ+, and these interactions modify the extent of e–f mixing and thus the relative intensities of R and P lines on one hand and the Q lines on the other. These observations of the Stark effect enable perturbation maxima to be located and thus allow relatively unperturbed energy levels to be identified. Constants from these levels of B1Π have been determined from a weighted least squares fit to 1776 lines of the B1Π – X1Σ+ transition as follows:[Formula: see text]