ANALYSIS OF PERTURBATIONS OBSERVED IN THE FT SPECTRA OF $CuCl_{2}$

Author Institution: Laboratoire de Spectrom\'etrie Ionique et Mol\'eculaire, CNRS et Universit\'e Lyott-I (UMR 5579), Campus la Doua; Physical and Theoretical Chemistry Laboratory, Oxford UniversityAbnormally large e-f separations have been observed in the $(v_{1},0,v_{3})$ levels of the ground $X^{2}\Pi_{g(3/2)}$, state of $CuCl_{2}$ about $2500\;cm^{-1}$ above the lowest vibrational level (0,0,0). The largest splitting are accompanied by extra lines in the dispersed fluorescence spectra. Some of the extra lines have resolvable Cu hyperfine structure; they are assigned as transitions to levels winch result from mixing essentially between $^{2}\Pi_{g(1/2)}$ and a nearby $^{2}\Sigma_{g}$ state. We have used an effective Hamiltonian to model the $^{2}\Pi \sim ^{2}\Sigma$ interaction and derived molecular constants for the unknown $^{2}\Sigma$ state using a non-linear least-squares fitting routine. Taking an arbitrary value of the spin-orbit parameter $A_{\Pi}$ of-$300\;cm^{-1}$, we estimate the $^{2}\Sigma$ state to lie around $3000\;cm^{-1}$ above the (0,0,0) level of the $X^{2}\Pi_{g(3/2)}$ ground state