Projectile-charge dependence of quasi-free-electron bremsstrahlung

Abstract

Continuum x rays induced by bombardments of a Be target with 20.14-MeV/amu protons and /sup 3/He/sup 2 +/ ions have been measured with a Si(Li) detector in the direction of 90/sup 0/ with respect to the incident beam. Difference in the x-ray--production cross sections multiplied by the x-ray energy h..omega.. )h..omega.. x (sigma/sub h/(h..omega..)/4-sigma/sub p/(h..omega..))) and ratio of the cross sections R(h..omega..) (equivalentsigma/sub h/(h..omega..)/4sigma/sub p/(h..omega..)) for the proton and /sup 3/He/sup 2 +/-ion impact, where sigma/sub h/(h..omega..) and sigma/sub p/(h..omega..) are the x-ray--production cross sections for proton and /sup 3/He/sup 2 +/-ion impact, respectively, were obtained as a function of the x-ray energy. Both the difference and the ratio show peaks in the region where the x-ray energy is equal to the relative kinetic energy between the projectile and the inner-shell electron to be scattered by the projectile. From the comparison with a theory of quasi-free-electron bremsstrahlung based on the impulse approximation, it is found that this peak corresponds to the maximum of the velocity-distribution function of the inner-shell electron. Furthermore, the contribution of radiative electron-capture process in the case of proton and /sup 3/He/sup 2 +/ impact is clearly found.