Systematics of cross sections for target K-vacancy production in heavy ion collisions
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 KÃ?Â± x-ray emission, L p , may be represented
by a universal function of the Geometrical ModelÃ¢Â?Â?s parameter X for Z2 = 17 - 32.
Multiple-vacancy KÃ?Â± 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
The scaling properties of the KÃ?Â± x-ray production cross sections were examined and a
semiempirical Ã¢Â?Â?universalÃ¢Â?Â? curve was deduced that reproduces the measured cross
sections to within Ã?Â±30% on average.
The relationship between the KÃ?Â± x-ray production cross sections and the geometrical
modelÃ¢Â?Â?s universal variable also was examined.
Advisor:Watson, Rand L.; Hardy, John C.; Natowitz, Joseph B.; Yennello, Sherry J.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:heavy ion k shell ionization cross section
Date of Publication:12/01/2006