Absolute doubly differential cross section measurements for 180° resonant elastic scattering of quasi-free electrons on B³⁺ ions

E.P. Benis^*
(James R. Macdonald Laboratory, Kansas State University, Manhattan, KS 66506-2601)

The resonant elastic scattering of quasi-free electrons on two-electron ions is investigated in collisions of 3--8 MeV B³⁺ ions with H₂ targets. High resolution spectra of the electron emission yield at 0° with respect to the beam direction were recorded utilizing a single stage hemispherical spectrograph with a focusing lens and a large position sensitive detector. Absolute doubly differential cross section measurements were obtained after calibrating the spectrograph overall efficiency, based on the bare B⁵⁺ ion induced binary encounter electron yield. Contributions from both metastable 1s2s³S and 1s²¹S ground states were accounted for using a new technique that allows for the precise determination of the 1s2s³S metastable component. Resonances superimposed on the binary encounter peak, were attributed to the formation of doubly-excited three-electron 1s2lnl' states. In addition, the 2s2p²²D triply-excited state populated from the B³⁺(1s2s³S) metastable part of the beam was also observed. R-matrix calculations were utilized within the impulse approximation and compared to the measurements. Overall fairly good quantitative agreement was found between the two.

^* In collaboration with T.J.M. Zouros, A. Gonzalez, T.W. Gorczyca and P. Richard

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Submitted to DAMOP 2002, May 2002 in Williamsburg, VA.

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