Rydberg structure within a broad resonance

Abstract

The interaction between a Rydberg series of weakly autoionising states and a very broad interloping resonance gives rise to characteristic effects in experimental spectra, namely the enhancement of upper series members, distortions (involving the possible appearance of minima) of the course of intensity in a series, fluctuations of width and the 'q-reversal' phenomenon. New experimental data at high resolution are reported. New theoretical formulae are proposed. Computations of line profiles based on these formulae reproduce many features of the data, in particular 'q-reversals' which may be detuned from the resonance energy of the broad level, fluctuations in the amplitude and width of the fine structure, etc. The 'q-reversal' effect is shown to play a central role in the interpretation of the interchannel coupling.