Analytical theory of charge-exchange-caused dips in spectral lines of He-like ions from laser-produced plasmas

Abstract

Previously we discovered a way for producing not-yet-available fundamental data on charge exchange between multicharged ions, virtually inaccessible by other experimental methods. It was based on the formation of dips (called x-dips) in spectral lines of hydrogen-like ions from laser-produced plasmas. At that time the x-dip phenomenon was considered to be possible only in spectral lines of hydrogenic systems: due to the existence of exact algebraic (higher than geometrical) symmetries relevant only to hydrogenic systems and to the corresponding two-Coulomb-centre systems (dicentres) having one electron. In the present paper, by engaging the concept of an approximate algebraic symmetry of two-electron dicentres (and of helium-like ions), we opened up the way to significantly broaden the scope of experimental studies of the x-dip phenomenon—to studies of possible x-dips in spectral line profiles emitted by He-like ions in laser-produced plasmas. We identified three prospective two-electron dicentres and calculated analytically theoretical positions of the x-dips in the corresponding He-like spectral lines (though future experimental and theoretical studies should not be limited to these three two-electron dicentres). Since future experimental and theoretical studies should not be limited to these three two-electron dicentres, we presented also a table containing 15 prospective He-like spectral lines and 10 corresponding solid targets for observing x-dips in laser-produced plasmas. For completeness we presented also a similar table for H-like lines. It presented 16 prospective H-like spectral lines and 11 corresponding solid targets for observing x-dips in laser-produced plasmas. From the shape of experimental x-dips it is possible to determine the rate coefficient of charge exchange in the corresponding dicentre, as demonstrated previously. Therefore the results of the present paper should very significantly extend the range of fundamental data on charge exchange between multicharged ions that can be obtained via the x-dip phenomenon, but not by any other method.