Electron-impact ionization ofMo+

Abstract

The electron-impact direct ionization cross section for ${\mathrm{Mo}}^{+}$ is calculated using both nonperturbative close-coupling and perturbative distorted-wave methods. When distorted-wave calculations for $4{d}^{5}\ensuremath{\rightarrow}4{d}^{4}$ direct ionization are added to distorted-wave calculations for $4p\ensuremath{\rightarrow}nl$ excitation-autoionization, the experimental measurements are found to be 60% lower than the theoretical predictions. Inclusion of nonperturbative three-body Coulomb effects, present in time-dependent close-coupling calculations, are found to reduce the distorted-wave $4{d}^{5}\ensuremath{\rightarrow}4{d}^{4}$ direct ionization cross section by 25%. This is by far the largest reduction yet seen when comparing the two methods for direct subshell ionization of an atomic positive ion in the ground state. However, when the close-coupling calculations for $4{d}^{5}\ensuremath{\rightarrow}4{d}^{4}$ direct ionization are added to distorted-wave calculations for $4p\ensuremath{\rightarrow}nl$ excitation-autoionization, the experimental measurements are still 45% lower than the theoretical predictions. Although we further investigate correlation effects in the initial target state and term-dependent potential effects in the ejected electron state in an attempt to understand the small magnitude of the experimental measurements, the discrepancy between theory and experiment remains unexplained.