Observation of an electric quadrupole transition in a negative ion: Experiment and Theory

TL;DR

This paper reports the first direct experimental observation of an electric quadrupole transition in a negative ion, specifically bismuth, supported by theoretical calculations that agree closely with the experiment.

Contribution

It presents the first experimental detection of an electric quadrupole transition in a negative ion and provides a hybrid theoretical approach for accurate predictions.

Findings

Successful observation of the E2 transition in Bi$^-$

Excellent agreement between experiment and theory

Enhanced understanding of forbidden transitions in negative ions

Abstract

The first direct experimental observation of an electric quadrupole ($\textit{E}$2) transition between bound states of an atomic negative ion has been made. The transition was observed in the negative ion of bismuth by resonant (1+1) photodetachment from Bi$^-$ $^3\textit{P}_2$ via excitation of the Bi$^-$ $^3\textit{P}_0$ fine structure state. The $\textit{E}$2 transition properties were independently calculated using a hybrid theoretical approach to account for the strong multi-level electron interactions and relativistic effects. The experimental and theoretical results are in excellent agreement, providing valuable new insights into this complex system and forbidden transitions in negative ions.