Electron-Impact Ionization of Neon at Low Projectile Energy: An Internormalized Experiment and Theory for a Complex Target

As a fundamental test for state-of-the-art theoretical approaches, we have studied the single ionization ($2p$) of neon at a projectile energy of 100 eV. The experimental data were acquired using an advanced reaction microscope that benefits from high efficiency and a large solid-angle acceptance of almost $4\pi$. We put special emphasis on the ability to measure internormalized triple-differential cross sections over a large part of the phase space. The data are compared to predictions from a second-order hybrid distorted-wave plus $R$-matrix model and a fully nonperturbative $B$-spline $R$-matrix (BSR) with pseudostates approach. For a target of this complexity and the low-energy regime, unprecedented agreement between experiment and the BSR model is found. This represents a significant step forward in the investigation of complex targets.

Figure 1

Three-dimensional triple-differential cross section for $2p$ ionization of neon. The experimental pattern on the left is compared with the BSR predictions on the right. The scattering angle is ${\theta }_{e1}=-10°\pm 1.5°$, and the ejection energy is $E_{e2}=8\mathrm{eV}\pm 2.0\mathrm{eV}$.

Figure 2

3DCS Ne($2p$) for ejection energies (columns) $E_{e2}=2\mathrm{eV}\pm 0.5\mathrm{eV}$ [(a)–(d)], $E_{e2}=5\mathrm{eV}\pm 1.5\mathrm{eV}$ [(e)–(h)], $E_{e2}=8\mathrm{eV}\pm 2.0\mathrm{eV}$ [(i)–(l)] and $E_{e2}=16.5\mathrm{eV}\pm 2.0\mathrm{eV}$ [(m)–(p)] for scattering angles of ${\theta }_{e1}=-5°\pm 0.5°$, $-10°\pm 1.5°$, $-15°\pm 1.5°$ and $-20°\pm 1.5°$ (top to bottom). The left panels are for the coplanar geometry, the center panels for the perpendicular plane, and the right panels for the full-perpendicular plane. Continuous line: BSR model, dashed line: DWB2-RM. Error bars denote the statistical error of the data.