Rotational band contour analysis in the B←X system of chlorobenzene cation prepared by resonance enhanced multiphoton ionization

Abstract The rotational structure of some vibronic bands of the B←X system of the chlorobenzene cation (φCl + ) has been studied by computation of rotational band contours. For the first time contours for ions prepared by resonance enhanced multiphoton ionization (REMPI), with a restricted (or non-equilibrium) rotational excitation have been analysed. Using the mass selectivity of the REMPI method, the relative contributions from the two principal isotopes 35 Clφ and 37 Clφ have been taken into account. For this purpose the excited state rotational constants of 37 Clφ have been determined. The ionic bands are shown to be A type which agrees with our vibrational assignments.