X-ray production in heavy-ion—atom collisions:3dσand4fσelectron promotion

In this paper, a systematic study of x-ray production in ion-atom collisions is presented for electron promotion by both $3d\sigma$ and $4f\sigma$ molecular orbitals. $L$ x-ray production cross sections and high-resolution $L$ x-ray spectral measurements are presented for ${\mathrm{P}}^{+}$, ${\mathrm{S}}^{+}$, ${\mathrm{Cl}}^{+}$, ${\mathrm{Ar}}^{+}$, and ${\mathrm{K}}^{+}$ projectiles incident on Ar and C${\mathrm{H}}_4$ gas targets for projectile energies between 15 and 200 keV. Average values of the fluorescence yield and total $L$-shell ionization cross sections are determined. A dramatic $Z$ dependence observed in the x-ray production cross section is attributed to changes in fluorescence yield. Theoretical calculations of fluorescence yield are found not to agree with experimentally determined values. Finally, inner-shell vacancy production by $3d\sigma$ electron promotion is found to be much less efficient than $4f\sigma$ electron promotion for the collision systems studied in this paper.