Systematics of $K\alpha$ x-ray satellite structure

Spectra of $K$ x rays emitted from a variety of solid targets (atomic number $Z_2=17–32$) under bombardment by fast heavy ions (atomic number $Z_1=6–83$) at $2.5–25\mathrm{MeV}∕\mathrm{amu}$ were measured in high resolution using a curved crystal spectrometer. The spectra were analyzed in order to examine the dependence of $K\alpha$ x-ray satellite structure on the Geometrical Model’s universal variable $X_n$. Scaling rules were established for the apparent average $L$-shell spectator vacancy fraction at the time of $K\alpha$ x-ray emission, the satellite peak centroids, and the satellite peak widths.

Figure 1

Spectra of $K$ x rays emitted from a thick metallic Co target under bombardment by $6\mathrm{MeV}∕\mathrm{amu}$ beams of (a) C, (b) Ne, (c) Ar, and (d) Kr. The vertical dashed lines indicate the energy positions of the $K{\alpha }_1$ and $K{\alpha }_2$ diagram lines.

Figure 2

Spectra of $K$ x rays emitted from a thick metallic Ti target under bombardment by Ar projectiles at (a) $2.5\mathrm{MeV}∕\mathrm{amu}$, (b) $6\mathrm{MeV}∕\mathrm{amu}$, (c) $15\mathrm{MeV}∕\mathrm{amu}$, and (d) $25\mathrm{MeV}∕\mathrm{amu}$. The vertical dashed lines indicate the energy positions of the $K{\alpha }_1$ and $K{\alpha }_2$ diagram lines.

Figure 3

(Color online) Spectrum of chlorine $K$ x rays emitted from a thick KCl target bombarded by $6\mathrm{MeV}∕\mathrm{amu}$ Kr ions. The circles represent the measured data points, while the solid lines represent the overall fit (red), the contributions from $K{\alpha }_1$ and $K{\alpha }_2$ satellites (blue and brown, respectively), and the combined contribution from the $K{\alpha }_1$ and $K{\alpha }_2$ diagram lines (purple). The dashed line (gray) represents the background.

Figure 4

(Color online) Apparent average $L$-vacancy fractions at the time of $K\alpha$ x-ray emission $\left(p_L^x\right)$, plotted as a function of the universal variable $\left(X_n\right)$ determined using Eq. (4) for $n=2$. The data points represent the results of measurements involving a variety of solid targets (atomic number $Z_2=17–32$) under bombardment by fast heavy ions (atomic number $Z_1=6–83$) at $2.5–25\mathrm{MeV}∕\mathrm{amu}$, while the solid line represents the best-fit logistic curve. The dashed curve represents the $L$-vacancy fractions at the time of collision, predicted by the Geometrical Model [6].

Figure 5

Spectra of chlorine $K\alpha$ x rays excited by $6\mathrm{MeV}∕\mathrm{u}$ Xe ions, measured using (a) a solid KCl target and (b) ${\mathrm{Cl}}_2$ gas. The latter spectrum shows a significantly higher degree of both $L$-shell and outer-shell ionization of the target atoms.

Figure 6

(Color online) Dependence on the apparent average $L$-vacancy fraction at the time of $K\alpha$ x-ray emission $\left(p_L^x\right)$ of the energy shifts of copper $K\alpha L^i$ satellite peaks $(i=1,2,3,4,5,6,7)$ relative to the corresponding $K\alpha L^0$ satellite peaks. Symbols represent the measured data points (weighted averages of $K{\alpha }_1$ and $K{\alpha }_2$ shifts), while the solid curves are the corresponding best-fit straight lines intersecting the ordinate at the values predicted by multiconfigurational Dirac-Fock calculations for zero outer-shell vacancies [13]. The crosses represent the predictions of Ref. 19.

Figure 7

(Color online) Energy shift of $K\alpha$ satellite peaks due to outer-shell vacancies divided by the apparent average $L$-vacancy fraction at the time of $K\alpha$ x-ray emission $\left(p_L^x\right)$ as a function of the associated number of spectator $L$ vacancies $\left(i\right)$ and the target atomic number $\left(Z_2\right)$. (See text for details.)

Figure 8

(Color online) Dependence of the satellite peak widths in excess of the instrumental resolution $\left(\Delta \sigma \right)$ on the associated number of spectator $L$ vacancies $\left(i\right)$ and the target atomic number $\left(Z_2\right)$. The error bars represent sample standard deviations. (See text for details.)