$K\alpha$ satellite and hypersatellite distributions of Ar excited in heavy-ion collisions

Spectra of $K\alpha$ x rays emitted from Ar gas at atmospheric pressure under bombardment by $10\mathrm{MeV}∕\mathrm{amu}$ heavy ions (atomic number 6–79) were measured in high resolution using a curved crystal spectrometer. Values of the apparent average fraction of $L$ vacancies at the time of $K\alpha$ x-ray emission $\left(p_L^x\right)$ were determined from the observed $K\alpha$ satellite and hypersatellite intensity distributions. A systematic comparison of the $p_L^x$ values for the monatomic gas Ar with those obtained previously for a variety of solid targets provided a quantitative assessment of the role interatomic transitions play in the $L$-vacancy transfer process that occurs prior to $K$ x-ray decay.

Figure 1

(Color online) Measured spectra of x rays emitted from Ar gas at a pressure of $1\mathrm{atm}$ under bombardment by $10\mathrm{MeV}∕\mathrm{amu}$ ions (as labeled). Positions of the $K{\alpha }_1$ and $K{\beta }_1$ diagram transitions are indicated by the vertical dashed lines. The solid circles show the raw spectra, while the solid lines simply connect the data points. One exception is the spectrum obtained with sulfur projectiles, where the line shows the corrected spectrum after subtraction of estimated contributions of sulfur x rays due to $M\to K$ transitions.

Figure 2

(Color online) Measured spectrum of $\mathrm{Ar}K$ x rays induced by $10\mathrm{MeV}∕\mathrm{amu}$ Ta projectiles. For x-ray energies from $3165\text{to}3347\mathrm{eV}$ and from $3348\text{to}4384\mathrm{eV}$, the number of counts per channel has been multiplied by factors of 2 and 4, respectively.

Figure 3

(Color online) Fitted $K\alpha$ satellite spectra of Ar induced by (a) Au and (b) Fe projectiles at $10\mathrm{MeV}∕\mathrm{amu}$. The measured data points are shown as solid black circles, while the thick solid (red) line represents the overall fit. The background is shown as a thick dashed (gray) line, while the thin solid (green) line outlines the contributions from the diagram x rays. The thin dashed (blue) lines represent the individual satellites or their major components (as labeled).

Figure 4

(Color online) The apparent average fraction of $L$ vacancies at the time of $K\alpha$ x-ray emission $\left(p_L^x\right)$ as a function of the universal variable $X_2$. The hollow (red) and solid (green) circles represent $p_L^x\left(K{\alpha }^s\right)$ and $p_L^x\left(K{\alpha }^h\right)$] from Table . The thin solid (red) line and the thin dashed (green) line show the corresponding best-fit logistic curves. The thick dashed line shows the geometrical model’s prediction of $p_L$ [Eq. (4)], the average fraction of $L$ vacancies produced in the collisions, while the thick solid (blue) line represents the best-fit logistic curve for $p_L^x$ values from $K\alpha$ satellites in measurements with solid targets (from Ref. 7).