STUDIES OF THE ELECTRONIC STATES OF THE BAF MOLECULE .1. EFFECTIVE CONSTANTS FOR 7 STATES BELOW 30000 CM-1

Laser-excited fluorescence and thermal emission spectra, recorded at high resolution by Fourier-transform spectrometry, have been analysed to yield new information about the ground-state, X2Σ+, and six of the lowest-lying electronic states of BaF. In the present paper we give values of the effective constants for X2Σ+, A’2, A2Π, B2Σ+, C2Π D2Σ+ and F2Π derived from an overall simultaneous fit to some 6470 lines assigned to rotational structure of 24 bands of 10 systems. Existing analyses are confirmed and extended, and a rotational analysis of levels of the state C2Π is given for the first time: the spin-orbit coupling constant in this state is found to increase unexpectedly rapidly with increasing v. The states A’2, A2Π and B2Σ+ interact strongly, and their mutual deperturbation, and the determination of their interaction constants form the subject of the following paper (Part II). © 1990 Taylor & Francis Ltd.