MOLECULAR-BEAM STARK SPECTROSCOPY OF THE C1-SIGMA+-X1-SIGMA+ (0,0) BAND OF YTTRIUM MONOCHLORIDE

The yttrium monochloride molecular (YC1) has been produced in a free yet molecular beam apparatus by chemical reaction in a laser-produced plasma. The origin band of the C (1)SIGMA+-X(1)SIGMA+ system of YCl was probed at the sub-Doppler resolution of 120 MHz using a ring dye laser to excite fluorescence. Spectra due to the two isotopomers (YCl)-Y-89-Cl-35 and (YCl)-Y-89-Cl-37 were obtained, and molecular constants determined. The following bond lengths were derived (YCl)-Y-89-Cl-35):r0 (X) = 2.384 78(36) angstrom, r0 (C) = 2.460 50(40) angstrom (2-sigma-error bound). Results for the ground state are in good agreement with those recently reported by Xin et al. [J. Mol. Spectrosc. 148, 59 (1991)]. The permanent electric dipole moments for both the X and C states were determined by performing molecular beam Stark spectroscopy on the lines P(1) and R(0), respectively. Values of 2.587 (29) D (X state) and 3.258 (36) D (C state) were obtained. Results are compared with ab initio predictions of the molecular parameters, and a molecular orbital interpretation of the bonding is presented.