On the role of Penning ionization in photoassociation spectroscopy

We study the role of Penning ionization on the photoassociation spectra of He(23S1)–He(23S1). The experimental set-up is discussed and experimental results for different intensities of the probe laser are shown. For modelling the experimental results we consider coupled-channel calculations of the crossing of the ground state with the excited state at the Condon point. The coupled-channel calculations are first applied to model systems, where we consider two coupled channels without ionization, two coupled channels with ionization, and three coupled channels, for which only one of the excited states is ionizing. Finally, coupled-channel calculations are applied to photoassociation of He(23S1)–He(23S1) and good agreement is obtained between the model and the experimental results.