Electron Capture and Loss Cross Sections of Fast Bromine Ions in Gases

Abstract

Br ions with energies of 13.9 and 25 MeV from the Oak Ridge tandem accelerator have been used to measure ionic charge-state distributions in dilute gas targets of H2, He, and Ar. A least-squares technique has been developed to obtain complete sets of electron charge-exchange cross sections from any number and range of measured nonequilibrium charge distributions. Characteristic irregularities, which originate in the atomic shell structure of the Br ions, have been found in the cross sections for capture of a sing]. e electron. Multiple electron capture and loss, as well as equilibrium charge distributions, are discussed,

Charge States and Charge-Changing Cross Sections of Fast Heavy Ions Penetrating Through Gaseous and Solid Media

“…Lo and Fite (1970) (q) is sometimes interrupted at the particular charge q = 7, and a (7,6) may lie considerably below a (6,5). Clear evidence for that effect has been found by Datz et al (1970) for bromine ions and Betz et al (1971a) for iodine ions. Since charge state 7+ corresponds in both ion species to an electron configuration of a closed principal shell, the M and N shell, respectively, the anomaleous behaviour of a (7) has been interpreted as a shell effect.…”

“…We will briefly describe some of the aspects which are important for such an analysis. Datz et al (1970). It turned out that this method or a variation of it is often unsatisfactory.…”

“…Systematic measurements have been performed by the groups at Heidelberg (Betz et al, 1966;Moller et al, 1968), Oak Ridge (Moak et al, 1968;Datz et al, 1970), and Burlington-Cambridge Betz and Wittkower, 1972a) with energetic beams of arsenic, bromine, and iodine. These and other results are listed in Table IV (Dmitriev et al, 1962b) .…”

“…A complete analysis comprises application of the wellknown leastsquares technique as discussed by Datz et al (1970) and Betz et al (1971a). The values of a(q,q') are determined from that technique in such a way that an exact integration of Eq.…”

Atomic collisions with relativistic heavy ions. III. Electron capture

“…In essence two methods, called he~e "thin t~get'"" and "thick t~get", 15 exist for" ext~acting cha~ge-changing cr"oss sections fr"om a measurement of cha~ge state yields as a function of tar"get thickness. In the thin-tar"get method, tar"gets ~e chosen that ~e thin enough so that the yield for" oneelectr"on attachment Or" loss is pr"opor"tional to the t~get thickness.…”