Nuclear dealignment in multiply ionized fast fluorine atoms recoiling in gases

The dealignment of the 5/2₁⁺ excited nuclear state of¹⁹F (E_x=197keV) has been determined for foil-excited fluorine ions of energies 3 and 6 MeV recoiling in He, N₂ and Ar gases using backscatter-coincidence excitation with He⁺⁺ and the recoil-distance technique. The observed decay of nuclear alignment with increasing gas pressure was interpreted in a microscopic collision model using theories of statistically perturbed angular correlations. The strong velocity dependence of the dealignment cross section indicates the dominance of charge exchange, e.g. capture, processes in producing the ionic states of strong hyperfine interaction.Work supported in part by Bundesministerium für Forschung und Technologie.