Effects of multiple ionization on the spectra of $L$ x rays excited in heavy-ion collisions

Spectra of $L$ x rays emitted from thick solid targets containing elements with atomic numbers ranging from 49 (In) to 67 (Ho) were measured in high resolution using a curved crystal spectrometer. The projectiles included heavy ions (Ne, Ar, Kr, and Xe) ranging in energy from 6 to $15\mathrm{MeV}∕\mathrm{amu}$. A scaling rule was established for the apparent average fraction of $M$ vacancies at the time of $L$ x-ray emission and the result was compared to one obtained previously for the apparent average fraction of $L$ vacancies at the time of $K$ x-ray emission. The apparent degree of $L$-shell ionization at the time of $L$ x-ray emission was examined as a function of target atomic number (for $6\mathrm{MeV}∕\mathrm{amu}$ Kr projectiles), projectile atomic number (for an ${}_{51}\mathrm{Sb}$ target), and projectile energy.

Figure 1

(Color online) Spectra of $L$ x rays emitted from thick solid targets (as indicated) under bombardment by $6\mathrm{MeV}∕\mathrm{amu}$ Kr ions.

Figure 2

(Color online) Spectra of $L$ x rays emitted from a thick solid target of Sb under bombardment by fast heavy ions. The projectile species is indicated along with its energy in MeV/amu enclosed in parenthesis. The vertical dashed lines indicate, in order of increasing energy, the centroids of the $L{\alpha }_1$, $L{\beta }_1$, and $L{\beta }_2$ diagram peaks and the $L_3$ absorption edge.

Figure 3

(Color online) Solid circles: Measured spectra of Sb $L$ x rays obtained under bombardment of a thick solid Sb target by $10\mathrm{MeV}∕\mathrm{amu}$ Ne (top) and $6\mathrm{MeV}∕\mathrm{amu}$ Kr ions (bottom). Lines: Overall fitting function (thick solid red) and its components (thin dashed blue (brown), thin solid green (pink), and thick dashed gray—see text).

Figure 4

(Color online) The apparent average fraction of $M$ vacancies at the time of $L$ x-ray emission $\left(p_M^x\right)$ as a function of the universal variable (Table ) for various targets employed in the measurements. (Both quantities are dimensionless.) The solid line represents the best fit of a logistic curve to the data points, while the dashed line represents $p_L^x$ as a function of $X_2$ [Eq. (1)]. The inset shows the residuals (i.e., the deviations of the data points from the fitted curve).

Figure 5

(Color online) Relative intensities of the $L^h$ x-ray components as a function of target atomic number for $6\mathrm{MeV}∕\mathrm{au}$ Kr projectiles. The lines are drawn to guide the eye.

Figure 6

(Color online) The apparent average number of $L$ vacancies at the time of $L$ x-ray emission as a function of target atomic number for $6\mathrm{MeV}∕\mathrm{amu}$ Kr projectiles.

Figure 7

(Color online) Projectile atomic number dependence of the apparent average number of spectator $L$ vacancies at the time of $L$ x-ray emission.