Target $K$-vacancy production by $2.5\text{to}25\mathrm{MeV}∕\mathrm{amu}$ Ar, Kr, and Xe ions

Cross sections have been measured for $K\alpha$ x-ray production in targets of Al, Ti, Cu, Zr, Ag, Sm, and Ta by Ar, Kr, and Xe ions ranging in energy from $2.5\text{to}25\mathrm{MeV}∕\mathrm{amu}$. In addition, the degree of simultaneous $L$-shell ionization and the enhancement of the $K\alpha$ diagram lines due to secondary ionization processes were assessed by performing high-resolution spectral measurements on Al, Ti, V, Co, and Cu targets. This information was used to correct for the $K\alpha$ x-ray yield produced by electron bombardment and photoionization, and to calculate the fluorescence yields needed to convert the $K\alpha$ x-ray production cross sections into $K$-vacancy production cross sections. The resulting cross sections were compared with the predictions of the perturbed stationary state approximation with corrections for projectile energy loss, Coulomb deflection, and relativistic effects (ECPSSR theory). Also, the scaling properties of the $K\alpha$ x-ray production cross sections were examined and a semiempirical (universal) curve was deduced that reproduces the measured cross sections to within $\pm 30\%$ on average.

Figure 1

(Color online) Comparison of Ti $K\alpha$ x-ray spectra, excited by $25\mathrm{MeV}∕\mathrm{amu}$ Kr ions, obtained with the low-resolution Si(Li) detector and the high-resolution curved crystal spectrometer. The various components that contribute to the spectra are indicated.

Figure 2

(Color online) Spectra, obtained with the Si(Li) detector, of the $K\beta$ region of Ag excited by $25\mathrm{MeV}∕\mathrm{amu}$ (a) Ar, (b) Kr, and (c) Xe ions. The two vertical lines delineate the average energy positions of the $K{\beta }_1$ and $K{\beta }_2$ diagram lines.

Figure 3

(Color online) Comparison of the experimental results for Al and Ti with the predictions of the ECPSSR theory. The theoretical curves are for Ar (blue dashed), Kr (red dotted), and Xe (green dot-dashed) projectiles. The solid curve shows the ECPSSR predictions for protons.

Figure 4

(Color online) Comparison of the experimental results for Cu, Zr, and Ag with the predictions of the ECPSSR theory. The theoretical curves are for Ar (blue dashed), Kr (red dotted), and Xe (green dot-dashed) projectiles. The solid curve shows the ECPSSR predictions for protons. (The experimental error bars are smaller than the size of the data points.)

Figure 5

(Color online) Comparison of the experimental results for Sm and Ta with the predictions of the ECPSSR theory. The theoretical curves are for Ar (blue dashed), Kr (red dotted), and Xe (green dot-dashed) projectiles. The solid curve shows the ECPSSR predictions for protons. (The experimental error bars are smaller than the size of the data points.)

Figure 6

(Color online) The sets of $K\alpha$ x-ray production cross sections divided by the single-vacancy fluorescence yields, as a function of speed ratio (shown separately for each projectile).

Figure 7

(Color online) The data in Fig. 6 multiplied by the scaling factor $B_K^2$ for each target, as a function of speed ratio (shown separately for each projectile).

Figure 8

(Color online) The fully scaled $K\alpha$ x-ray production cross sections as a function of speed ratio. A semiempirical “universal” curve has been fit to the data points.

Figure 9

(Color online) A graph showing the dependence of the projectile effective charge on the projectile atomic number. The solid curve has been fit to the data points.