Experimental and theoretical L-shell ionization cross sections of heavy atoms by impact of Si ions

OSWAL, M.; KUMAR, SUNIL; SINGH, UDAI; SINGH, G.; SINGH, K.P.; MEHTA, D.; MÉNDEZ, A.; MITNIK, D.M.; MONTANARI, C.C.; MITRA, D.; NANDI, T.

RADIATION PHYSICS AND CHEMISTRY (OXFORD)

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020

0969-806X

We present a theoretical and experimental study of the subshell resolved L-shell ionization of relativistic targetssuch as 73Ta, 78 Pt, 90Th, and 92U. The measurements of x-ray production cross sections by (84-140 MeV) Si+q ions(q=8; 12), were held at the Inter-University Accelerator Centre of New Delhi. Multiple-hole fluorescence andCoster-Kronig yields were used to obtain the Li(i = 1-3)ionization cross sections from the measured x-rayproduction cross sections of Ll, Lα, and Lβ, Lη, and Lγ lines. The experimental results are compared with abinitio theoretical calculations by means of the shell-wise local plasma approximation (SLPA). This model uses thequantum dielectric formalism to obtain the total ionization cross sections from an initial ground state. The wavefunctions and binding energies of the different targets were obtained by solving the fully-relativistic Dirac equationusing the HULLAC code package. These calculations are based on first-order perturbation theory with a centralfield, including Breit interaction and quantum electrodynamics corrections. The present SLPA ionizationcross sections of the L-shell are found to be independent of the charge state of the Si ions. The experimentalobservations display also quite similar character if the correct mean projectile charge state inside the targetis used for including the multiple ionization effect during ion-solid collisions. A general good agreementbetween the experimental measurements and full theoretical calculations supports the reliability of presentresults. The comparison also includes the well-known ECPSSR and ECUSAR semi empiricalapproximations. We noted that the ECUSAR results agree well with the SLPA, while the ECPSSR crosssections are rather low.