Rovibrational states of ClHCl- isotopologues up to high J: a joint theoretical and spectroscopic investigation

Abstract

Explicitly correlated coupled cluster theory at the CCSD(T )-F12b level (T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys., 2007, 127, 221106) and two precise spectroscopic parameters (K. Kawaguchi, J. Chem. Phys., 1988, 88, 4186) were used to construct an accurate near-equilibrium analytical potential energy function (PEF) for the highly anharmonic centrosymmetric hydrogen-bonded complex ClHCl- (R-e = 3.1153 angstrom). From variational calculations with that PEF, a large number of rovibrational energies of different isotopologues up to high values of the rotational quantum number J was obtained. Theory helped with the assignment of lines observed by IR diode laser spectroscopy in the nu(1) + nu(3) combination band of (ClHCl-)-Cl-35-Cl-35 and (ClHCl-)-Cl-37-Cl-35 and enabled us to elucidate rather subtle patterns of rovibrational interactions. Furthermore, transition dipole moments were predicted and analysed as well as unusual isotopic effects.