The electronic spectra of HCl and HF

The absorption spectra of HCl and HF have been photographed at high dispersion in the vacuum ultraviolet region. In the HCl spectrum, many new band systems have been identified and 18 vibrational levels of the ionic B1Σ state have been observed. The B1Σ state is found to interact strongly with the Rydberg states. Although many bands have been analysed, much of the HCl spectrum remains unassigned. Analyses of bands associated with the lowest discrete 1Π and 3Π states of HF are presented together with the analyses of two 1Π–X1Σ band systems which lie between the first and second ionization limit. The spectrum of HF is very complex and little of it has been analysed even though the spectral lines are sharp and well resolved. The theoretical problems in understanding the spectra of HCl and HF are discussed.