Photoionization microscopy in terms of local frame transformation theory

TL;DR

This paper develops a theoretical framework combining local frame transformation and quantum defect theory to analyze photoionization microscopy in alkali-metal atoms under electric fields, providing a new way to interpret experimental observables.

Contribution

It introduces a generalized approach for calculating quantum defect parameters in combined Coulombic and Stark potentials using eigenchannel R-matrix theory, enabling more accurate microscopy predictions.

Findings

Validated the local frame transformation approach against Harmin-Fano theory.

Provided detailed calculations of quantum defect parameters in Stark fields.

Enhanced understanding of photoionization processes in alkali-metal atoms.

Abstract

Two-photon ionization of an alkali-metal atom in the presence of a uniform electric field is investigated using a standardized form of local frame transformation and generalized quantum defect theory. The relevant long-range quantum defect parameters in the combined Coulombic plus Stark potential is calculated with eigenchannel R-matrix theory applied in the downstream parabolic coordinate $\eta$. The present formulation permits us to express the corresponding microscopy observables in terms of the local frame transformation, and it gives a critical test of the accuracy of the Harmin-Fano theory permitting a scholastic investigation of the claims presented in Zhao {\it et al.} [Phys. Rev. A 86, 053413 (2012)].