Subshell contributions to electron capture into the continuum in MeV/u collisions of deuterons with multielectron targets

The process of the capture of a target electron into the projectile continuum (ECC) is investigated both experimentally and theoretically for collisions of 1.25–6.00 MeV deuterons with multielectron gas targets. Double-differential cross sections (DDCS), $d^2\sigma /d\mathrm{\Omega }dE$, of the ECC cusp-shaped electron peak involving He, Ne, and Ar gas targets were measured at the emission angle of zero degrees with respect to the ion-beam velocity. Corresponding DDCS calculations, obtained using continuum distorted-wave (CDW) and continuum distorted-wave eikonal initial-state (CDW-EIS) theories, were critically compared to the measurements. The role of each atomic subshell of the multielectron Ne and Ar targets is examined employing the CDW-EIS theory with numerical target wave functions, which is found to best agree with the measurements.

Figure 1

DDCS electron spectra measured at zero degrees with respect to the projectile velocity for collisions of 1.50 MeV deuterons with He gas targets. Symbols: experimental data. Lines: DW theories' calculations (see text). The spectral locations of the cusp and BEe peaks are depicted.

Figure 2

DDCS electron spectra measured at zero degrees with respect to the projectile velocity for collisions of 1.50 MeV protons with He gas targets. Triangles: experimental data obtained in this work. Diamonds: experimental data retrieved from [23]. Multicolored circles: the four overlapping energy windows covering the ECC cusp peak, the weighted average of which corresponds to the triangles.

Figure 3

Electron DDCS measured at zero degrees with respect to the projectile velocity for collisions of [top] 1.50 MeV, [middle] 3.00 MeV, and [bottom] 6.00 MeV deuterons with [right] Ne and [left] Ar gas targets. The symbols correspond to the experimental data and the lines to the calculations of (blue dash-dot-dotted line) CDW-post, (green dash-dotted line) CDW-EIS-prior, (black dashed line) CDW-post-hybrid, and (red line) CDW-EIS-numerical.

Figure 4

Electron DDCS measured at zero degrees with respect to the projectile velocity for collisions of 1.25–2.00 MeV deuterons with Ar (red) and Ne (blue) gas targets. The symbols correspond to the measurements and the lines to the calculations of the CDW-EIS-numerical theory. The small peak around 800 eV in the Ne spectrum of 2.00 MeV collision energy corresponds to the Ne-KLL Auger lines.

Figure 5

Contributions of the Ne [top] and Ar [bottom] atomic subshells to the formation of the ECC cusp peak in collisions with (from left to right) 1.25, 1.50, 1.75, 2.00, 3.00, and 6.00 MeV deuterons, corresponding to the CDW-EIS-numerical calculations. The break in the electron energy axes around the region of the pole of the cusp peak is to facilitate visibility. Note that the $1s$ contribution for Ar is multiplied by the factor of 100 for the collision energies of 1.25 and 1.50 MeV and by the factor of 10 for the collision energies of of 1.75, 2.00, and 3.00 MeV, respectively.