Quantum over-barrier reflection effects manifested in the photodetachment cross sections

TL;DR

This paper introduces a new formula for photodetachment cross sections near potential barriers, capturing quantum over-barrier reflection and tunneling effects, and demonstrates how these effects vary with barrier parameters.

Contribution

A novel formula that accurately describes quantum effects in photodetachment near barriers, extending standard theories to include over-barrier reflection and tunneling phenomena.

Findings

Quantum over-barrier reflection causes oscillations above barrier tops.

Quantum tunneling weakens oscillations below barrier tops.

Barrier parameters can be tuned via electric field and ion-surface distance.

Abstract

Photodetachment of H$^-$ near a potential barrier is studied. A new formula is presented for the cross sections induced by a barrier. The new formula describes two quantum effects near barrier tops. For energies near and above barrier tops, the quantum over-barrier reflection effects are included and the induced oscillations in the cross sections are still prominent; for energies near and below barrier tops, the quantum tunneling across barriers is taken into account and consequently the oscillations are weakened. For energies far away from the barrier tops, the new formula agrees with the standard closed-orbit theory. We demonstrate that a potential barrier of various width and location can be realized by placing a negative ion near a metal surface and applying an electric field pointing to the surface. The width and location of the barrier can be systematically changed by varying the electric field strength and the distance between the negative ion and the surface. Results are also presented for estimating the sizes and locations of aforementioned quantum effects in the cross sections.