New electronic transitions in the CH⁺ molecule

Abstract

The identification of new electronic transitions in the CH⁺ molecule is described. Laser photofragment spectra previously recorded near 540 nm arise from electronic transitions between triplet energy levels which lie just below the C⁺(² P) + H(² S) dissociation limit and a weakly-bound long-range triplet state which correlates to the C(³ P) + H⁺ dissociation asymptote. In addition, it is proposed that at least part of the reported CH⁺ photofragment spectrum near 350 nm is due to transitions between analogous near-threshold singlet levels and weakly-bound long-range singlet states which correlate to C(¹ D) + H⁺. A bound-bound-free mechanism is invoked to explain the observations in which laser excitation is followed by radiative decay to the continua just above the lowest dissociation asymptote. This results in the formation of C⁺ ions which are detected