Electron-impact detachment from S<Superscript>-</Superscript>

Absolute cross sections for single and double electron-impact detachment of the S^- ion have been investigated over collision energy ranges of 0-60 eV and 0-30 eV, respectively. The experiment was performed at the ion storage ring, CRYRING. The threshold energies were measured to be 6.6 eV for single detachment and 19.8 eV in the case of double detachment. The single detachment cross section has a maximum of 6.7 x 10^-16 cm² at 30 eV. The double detachment cross section was studied only in the threshold region. No sharp structures were observed in either of the cross sections.Received: 24 April 2003, Published online: 29 July 2003PACS: 34.80.Dp Atomic excitation and ionization by electron impact - 34.80.Kw Electron-ion scattering; excitation and ionization     

Electron impact single detachment on the F - ions using the heavy ion storage ring CRYRING: Cross-section determination

Electron Impact Single Detachment (EISD) of F^- has been studied using the heavy ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm, Sweden. F^- ions stored in the ring were merged with an electron beam in one of the ring sections. Neutral F atoms produced in the EISD process were detected in the zero-degree direction using a surface barrier detector. The threshold for the detachment process was found to be around 7.6 eV, thus more than twice the binding energy of F^-. The cross-sections increased smoothly up to 55 eV where it reached a maximum of 1.9×10 ^-16 cm ² . At higher energies a slow decrease of the cross-section was observed, which follows the energy dependence predicted by the Bethe-Born approximation. The experiment showed that CRYRING can be used favourably for studies of anions, and several experiments are forthcoming. Received 14 June 2000 and Received in final form 11 September 2000     

Fine structure of As−

The energies of the As^? fine structure components 4p^{4 3} P ₁ and 4p^{4 3} P ₀ have been determined relative to the 4p^{4 3}P₂ ground state by using photodetachment electron spectroscopy. Fine structure splittings of ΔE(³ P ₁ ? ³ P ₂) = 125(3) meV and ΔE(³ P ₀ ? ³ P ₂) = 166(5) meV have been obtained. It is the first experimental determination of the energy of the J = 1 level and an improvement of the accuracy for the J = 0 level. Previous isoelectronic extrapolations are consistent with the experimental values.     

Threshold photodetachment in a repulsive potential

We report on the first experimental observation of a new threshold behavior observed in the 5(2)G partial channel in photodetachment of K(-). It arises from the repulsive polarization interaction between the detached electron and the residual K(5(2)G) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5(2)G) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.