The laser-induced fluorescence spectroscopy of yttrium monosulfide

We have investigated the laser-induced fluorescence (LIF) excitation spectra and dispersed fluorescence (DF) spectra of yttrium monosulfide (YS) in the energy range of 17860-20700 cm(-1). Rotational analyses indicated that almost all of the intense vibronic bands can be attributed to the new [19.38](2)Sigma(+) (upsilon') - X2 Sigma+ (upsilon '') transition system. The missing (1, 2), (2, 1) and (3,3) bands are caused by their very small Franck-Condon factors, as confirmed by our calculations. The new (2)Sigma(+) state has been suggested to arise from the electronic configuration of (core)1 sigma(2)2 sigma(2)1 pi(3)3 sigma 2 pi, featuring a charge-transfer nature. Moreover, the spin-rotation parameter gamma for the newly observed (2)Sigma(+) state has been determined to be 0.0206 cm(-1), the magnitude of which is larger than the known gamma(X-2 Sigma(+)) (0.001427 cm(-1)) but smaller than gamma(B-2 Sigma(+)) (-0.1515 cm(-1)). Crown Copyright (C) 2015 Published by Elsevier Inc. All rights reserved.