Photodissociation of doubly excited states of molecular hydrogen studied by polarization measurement of Lyman-α fluorescence

Abstract

The polarization anisotropy of Lyman-α fluorescence in the photodissociation of the doubly excited states of H2 has been measured in the 27–38 eV energy range. It has been calculated taking into account the dissociation probabilities of the various molecular states involved in the process and the depolarization due to collisional effects. The agreement between experiment and theory is very good; it shows the importance of interferences and gives confidence in the analysis of the process. The fluorescence polarization anisotropy has been calculated classically in the case of a dissociation leading to H(2pπ) + H(2pσ) excited fragments.

Dissociation dynamics of doubly excited states of molecular hydrogen

“…[23]. As the polarization is sensitive to the symmetry of the dissociative states, this agreement can be considered as an additional proof of the above analysis [24].…”

Two-colour experiments in the gas phase

“…The dissociation mechanisms of this prototypical molecule have been largely investigated at lower excitation energies, and dissociation into excited neutral atoms was studied up to hν = 60 eV by fluorescence spectroscopy in order to probe the excited states (e.g. [38,39]). In contrast to these studies, the photoionization of the excited atoms by the optical laser and the analysis of the photoelectron spectrum were used in the experiment at FLASH in order to characterize the production of excited states.…”

Atomic polarization in the photodissociation of diatomic molecules

“…As a result, it has been possible to undertake detailed theoretical calculations in order to predict many dynamical observables, including the photofragment angular momentum polarization, as a function of dissociation wavelength. 56,139,[144][145][146][147][148][149][150] The concurrent development of synchrotron radiation and VUV lasers has allowed many of these quantities to be probed experimentally. 65,87,88,147,[150][151][152][153] While certain recent studies have probed multi-photon dissociation of H 2 via high-lying Rydberg states, the discussion below focusses on single photon dissociation of H 2 just above its second dissociation limit (to form H(1s) + H(2s/2p) products).…”

“…56,139,[144][145][146][147][148][149][150] The concurrent development of synchrotron radiation and VUV lasers has allowed many of these quantities to be probed experimentally. 65,87,88,147,[150][151][152][153] While certain recent studies have probed multi-photon dissociation of H 2 via high-lying Rydberg states, the discussion below focusses on single photon dissociation of H 2 just above its second dissociation limit (to form H(1s) + H(2s/2p) products).…”