L- and M-shell X-ray production cross section measurements in ~(73)Ta and ~(78)Pt using B~(3+,4+)-ions of energies below and above the potential barrier

摘要

In this paper, we report the L- and M-shell X-ray production cross sections in Ta-73 and Pt-78 caused by the bombardment of 35 to 60 MeV B3+4+-ions. The energies of B-ions, below and above the potential barrier, were selected to study the effect on inner- and outer-shell ionization i.e. absolute X-ray production cross sections for various L- and M X-ray lines/group of lines (namely Ll, L alpha(2), L alpha(1), L beta(4,6), L beta(1), L beta(3), L beta(2,15), L beta(5,7,9,10), L gamma(5), L gamma(1), L gamma(2,3,8), L gamma(4,4), M xi(2,1), M delta + M3N1, M alpha(1,2) + M2N1, M beta + M eta, M gamma, Mm(11) (M3O1 + M3O4,5), Mm(12) (M2N4 + M1N3), Mm(21) (M2O1), Mm(22) (M2O4 + M1O2,3) and the change in the intensity ratios due to multiple ionization of M- and higher-shells. The present measurements were carried out at 16UD Pelletron Accelerator at Inter-University Accelerator Centre (IUAC) Delhi. The ion beams were bombarded on thin targets evaporated on an ultrapure carbon backing of 10 mu g/cm(2). The targets fixed on a steel ladder were placed in an evacuated ( 10(-6) Torr) scattering chamber at 45 degrees each to the beam direction and to the Si(Li) detector. The recorded L and M X-ray spectra were separately deconvoluted into various components of the L and M X-ray lines using the computer code after subtracting suitable background. The experimental results have been compared with the theoretical values by converting the L and M-subshell ionization cross sections based on the PWBA and ECPSSR direct-ionization theories taking into effect the sub-shell fluorescence yields, Coster-Kronig transition probabilities and transition rates based on Dirac-Fock and Dirac-Hartree-Slater models. In the present measurements (0.0641 = Z(1)/Z(2) = 0.0685), the velocity ratios v(1)/v(2pi) and the reduced ion velocity xi(pi) = 2v(1)/(theta(pi).v(2)p(i)) for p = L- or M-shell are in the range of 0.309 = v(1)/v2(Li) = 0.435 and 0.913 = xi(Li) = 1.316 and the ratios v(1)/v(2MI) and xi(Mi), for M-shell are in the range of 0.555 = v(1)/v(2Mi) = 0.790 and 2.575 = xi(Mi) = 3.779 respectively. To the best of our information, this study of B-ion impact on Ta-73 and Pt-78, near the potential barrier of the system which falls in the fast (xi(Li).= 1, xi(Mi) 1) collision regime, is being reported for the first time.