Electron capture and transfer ionization in collisions of H⁺and He²⁺ions with Fe atoms

Abstract

A crossed beam technique incorporating time-of-flight spectroscopy and coincidence counting of fast ion (atom)-slow ion collision products has been used to obtain for the first time separate cross sections for simple electron capture (charge transfer) and for transfer ionization in collisions involving Fe atoms. We have studied processes involving Fen+ formation in one-electron capture by 70-500 keV amu-1 H+ ions for n between 1 and 4 and both one and two electron capture by 37.5-360 keV amu-1 He2+ ions for n between 1 and 6. It is shown that, for the most part, total electron capture cross sections are dominated by contributions from transfer ionization processes rather than from simple charge transfer. The energy dependence of some of the measured cross sections exhibits interesting structure and the formation of the observed multicharged Fen+ ions is considered in terms of a model involving electron capture of either 4s, 3d or 3p target electrons together with electron removal through binary collisions at high velocities.

Ionization in collisions of fast H+and He2+ions with Fe and Cu atoms

“…(5) It was then possible to determine u9(i) in (4) using values of k(X9*)/1 from ( 5) where values of uq(e) are known from our previous measurements (Shah et al 1993, Bolorizadeh et al 1994 which in turn were normalized to absolute values measured by Freund et ad (1990).…”

Electron capture and multiple ionization in collisions of fast and ions with gallium atoms

“…In our previous measurements of electron capture in collisions with Fe and Cu (Patton et al 1994, Shah et al 1995b it should be noted that, in the case of H + impact, while for the relatively rapid decrease in 20 σ 11 for Ga compared with the corresponding cross sections in Fe and Cu (Patton et al 1994, Shah et al 1995b. For two-electron capture, the fast decrease in 20 σ 02 in Ga compared with the corresponding results for Fe and Cu (Patton et al 1994, Shah et al 1995b may also be related to the relative likelihood of 3p or 3d electron captures followed by Auger ionization.…”

“…The general role of such processes in impurity control and plasma diagnostics which are relevant to the design of next-step fusion devices has been summarized by Janev (1993). In previous work in this laboratory (Patton et al 1994, 1995, 1996, Shah et al 1995a, b, 1996a we have used a crossed-beam technique incorporating time-of-flight analysis and coincidence counting of the collision products to study electron capture and ionization in collisions of H + and He 2+ ions with Fe and Cu atoms within the energy range 38-1440 keV amu −1 . In these measurements, a specially developed oven source (Shah et al 1996b) was used to provide thermal energy beams of ground state 3p 6 3d 6 4s 2 5 D 4 Fe and 3p 6 3d 10 4s 2 S 1/2 Cu atoms.…”

Blocking Metal Accretion onto Population III Stars by Stellar Wind

“…The right scale of Figure 6 is β cx ,i ≡ σ cx,i wn sw for reference, and the values are comparable to β ph ,i on the right panel of Figure 3. Note that the charge exchange cross section for the neutral iron is not studied in the relative velocity of our interest (c.f., Patton et al 1994).…”