Ro-vibrational levels of the ground state of ICl have been measured in the range vx = 35-73 and Jx < 55 using three-stage polarization-labeling spectroscopy. When merged with established microwave and fluorescence data for the lower levels, these results lead to a self-consistent set of spectroscopic constants Gv, Bv, Dv and Hv for all levels vx ≤ 73. The highest Gv and Gv + FJ term values recorded are, respectively, 52.7 and 1.37 cm-1 below the dissociation limit. Coefficients of the long-range interaction I + Cl are determined by analysis of the outer wings of the RKR potentials for the X(0+) and A′(2) states. Electronic rotational interaction between X and the well-known A(1) state of ICl is shown to account for at least a major part of the Ω-doubling splitting observed in A: the electronic matrix element characterizing this interaction is shown to be strongly r-dependent, and reasons for this are reviewed. © 1985.
Brand, J. C. D., & Hoy, A. R. (1985). High vibrational levels of the X state of ICl, and the electronic-coriolis coupling of the X and A states. Journal of Molecular Spectroscopy, 114(1), 197–209. https://doi.org/10.1016/0022-2852(85)90348-0