Fine Structure and Predissociation in the Spectrum of Calcium Hydride

Abstract

IN 1925 Mulliken¹ reported a band system, emitted by the CaH molecule, and having a very unusual structure. It is composed of singlet P and R branches, which are abruptly cut off at P (11½) and R (9½). It was generally assumed that this band, shortly named the (C-band, corresponds to a ²C² transition, and that the non-appearance of doublet components in the series was caused by some peculiar unstable conditions in the activated ²* state. Later on², we were able to show that ²* suffers from predissociation into the continuous region of an activated ² level, causing the remarkable cut-off in the series at low pressure in the source of light.