An investigation of dissociative resonant photoionization in HCl and DO using two-dimensional photoelectron spectroscopy

Photoelectron spectra in the vicinity of the 2p(3/2,1/2) -> sigma* dissociative resonances in HCl and DCl have been recorded using two-dimensional photoelectron spectroscopy. The comprehensive data suggest that the explanation for the negative spectral contribution observed in an atomic line, which arises from autoionization following dissociation, might be more complex than the one proposed by Feifel et al (2000 Phys. Rev. Lett. 85 3133). These authors attributed this feature solely to continuum-continuum interference between resonant atomic and molecular Auger contributions, the latter occurring prior to complete dissociation, but resulting in an electron with the same kinetic energy as one produced in the atomic decay. The new data reveal a similar spectral feature in a region of the spectrum where this type of interference cannot occur. Consequently, an interference mechanism that does not require the energy of the resonant Auger electron be the same whether it is emitted before or after the molecule dissociates is indicated, such as the one discussed by Pahl et al (1998 Phys. Rev, Lett. 80 1865). Alternatively, the two-dimensional resonant enhancements, observed in the region of the negative spectral contribution, could be attributed to Auger decay to multiple final ion states, before the dissociating molecule has fragmented completely.