Systematics of cross sections for target K-vacancy production in heavy ion collisions

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Title: Systematics of cross sections for target K-vacancy production in heavy ion collisions
Author: Peng, Yong
Abstract: Cross sections for K -shell ionization by heavy ions have been determined from the measurements of target K x -ray yields . The measurements were performed with Ar , Kr , and Xe ions at energies from 2 .5 to 25 MeV /amu and self -supported metallic foil targets of Al , Ti , Cu , Zr , Ag , Sm , and Ta . The x -ray yields were measured with a Si (Li ) detector , while the projectile ions were counted in coincidence with the x -rays using a plastic scintillation detector . In addition , the amount of secondary K -shell ionization and the degree of simultaneous L -shell ionization in primary K -shell ionizing collisions were assessed by performing high -resolution x -ray measurements on targets of Al , Ti , V , Co , and Cu with a curved crystal spectrometer . The results of the high resolution measurements revealed that the apparent average Lshell spectator vacancy fraction at the time of K ? ? ? ? x -ray emission , L p , may be represented by a universal function of the Geometrical Model ? ? ? ? ? ?s parameter X for Z2 = 17 - 32 . Multiple -vacancy K ? ? ? ? fluorescence yields and corrections for K -shell ionization by secondary processes were determined with the aid of the high resolution spectra for the targets Al , Ti , and Cu . Fluorescence yields for the other targets were determined using an extrapolation procedure . The resulting K -vacancy production cross sections for 2 .5 to 6 MeV /amu projectiles were compared with a limited amount of available experimental data and shown to be in relatively good agreement . The ECPSSR predictions for all the targets except Al agreed reasonably well with experimental cross sections for Ar projectiles . The experimental cross sections for Kvacancy production in Al , Ti , Cu , Zr , and Ag were greatly deviated from the ECPSSR predictions . The cross sections for Kr on Sm and Ta were in good agreement with theory . The scaling properties of the K ? ? ? ? x -ray production cross sections were examined and a semiempirical ? ? ? ? ? ?universal ? ? ? ? ? ? curve was deduced that reproduces the measured cross sections to within ? ? ? ?30 % on average . The relationship between the K ? ? ? ? x -ray production cross sections and the geometrical model ? ? ? ? ? ?s universal variable also was examined .
URI: http : / /hdl .handle .net /1969 .1 /4700
Date: 2007-04-25


Systematics of cross sections for target K-vacancy production in heavy ion collisions. Available electronically from http : / /hdl .handle .net /1969 .1 /4700 .

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