Isotopic dependence of Born-Oppenheimer breakdown effects in diatomic hydrides: The B1Σ+ and X1Σ+ states of HCl and DCl

A numerical procedure for obtaining isotopically self-consistent radial Hamiltonian operators from spectroscopic line positions is applied to the X1Σ+ and B1Σ+ electronic states of H35Cl, H37Cl, D35Cl, and D37Cl. A simultaneous four-isotopomer, two-state least-squares fit of 8497 line positions yields Born-Oppenheimer potentials for both states and radial functions which describe adiabatic and nonadiabatic effects. Rotationally dependent energy shifts in the ground states of the four isotopomers are described by a single mass-reduced purely nonadiabatic radial function, qX(R). The assignments for the B-X system of D35Cl are extended and the first set of rotational assignments for D37Cl is presented. Synthetic calculations of the microwave line positions for TCl reproduce satisfactorily the experimental spectra.