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Cross sections for L x-ray production and L -subshell ionization by MeV electrons

1975; American Institute of Physics; Volume: 12; Issue: 4 Linguagem: Inglês

10.1103/physreva.12.1358

0556-2791

Y. K. Park, Mary T. Smith, W. Scholz,

Nuclear Physics and Applications

A systematic study of $L$ x-ray production and $L$-subshell ionization by MeV electron impact has been made. Cross sections were measured for 14 elements from Ba ($Z=56$) to ($Z=83$) at electron bombarding energies of 1.04, 1.39, and 1.76 MeV. Within the error limits there is no dependence on the electron energy. At all energies, measured $L$ x-ray production cross sections exhibit a gradual increase with atomic number. For the heavier elements, typical average values for the $L\ensuremath{\alpha}$, $L\ensuremath{\beta}$, and $L\ensuremath{\gamma}$ group are 70, 55, and 9 b, respectively. $L$-subshell ionization cross sections were derived from the $L\ensuremath{\alpha}$, $L\ensuremath{\beta}$, and $L\ensuremath{\gamma}$ x-ray production cross sections with the use of theoretical $L$-subshell fluorescence yields, Coster-Kronig yields, and radiative branching ratios. The total $L$-shell ionization cross section drops from 1200 b at Ba ($Z=56$) to 380 b at Bi ($Z=83$) with individual $L$-subshells contributing roughly in proportion to their electron number. The measured cross sections are in good agreement with the predictions of the binary-encounter collision model of Gryzi\ifmmode \acute{n}\else \'{n}\fi{}ski.