Absolute cross-section measurements for K-shell photoionization of Be-like C2+ ions have been performed in the photon energy range 292–325 eV. These measurements have been made using the photon–ion merged-beam endstation at the Advanced Light Source, Lawrence Berkeley National Laboratory. Absolute measurements compared with theoretical results from the R-matrix method indicate that the primary C2+ ion beam consisted of 62% ground-state (1s22s2 1S) and 38% metastable state (1s22s2p 3Po) ions. Reasonable agreement is seen between theory and experiment for absolute photoionization cross sections, resonance energies and autoionization linewidths of K-shell-vacancy Auger states.
We report the first experimental measurements of the effect of an applied field on the photoexcitation and autoionization of doubly excited states of helium. Ground-state photoionization spectra have been measured in the region below the He+(N=2) threshold with static electric fields of up to 84.4 kV/cm across the interaction region. The results are compared to the theoretical calculations of Chung et al. [J. Phys. B 34, 165 (2001)]], which are the only calculations available in this regime. Transitions to several states in the N=2, n=6 manifold are assigned, and a wealth of new structure is observed. Our data show that many more series are mixed in by the field than those predicted by theory.
We have measured the total cross section for
photodetachment of the Na- ion over the photon energy
range 30-51 eV. Electron detachment leads predominantly
to the production of Na+ ions in this energy range.
The structures in the measured cross section are
associated with correlated processes involving the
detachment or excitation of a 2p core electron, processes
which are often accompanied by the excitation of one or
more valence electrons. The most prominent feature in the
cross section is a strong resonance associated with the
excitation of a 2p electron from the core and a 3s
valence electron. As in previous experiments on double
excitation of valence electrons, electron correlation is
seen to play an important role in the dynamics of
negative ions.
Two resonances in the photodetachment spectrum of H, one just below the n = 3 threshold and the other just below the n =4 threshold, were observed decaying into H {n'=2)+e. The n =3 resonance shows a preference for the n'=2 channel when compared with total-detachment measurements. Fanoline-shape fits give central energies of 12.652+0.003 eV for H * (3) and 13.338+0.004 eV for H **(4). These values are in good agreement with current theoretical calculations. PACS number(s): 32.80.Fb, 31.50.+w, 32.80.Cy
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