Coherent control of the cooperative branching ratio for nuclear x-ray pumping

TL;DR

This paper explores how to coherently control nuclear x-ray pumping in ensembles of nuclei by manipulating cooperative decay, aiming to enhance nuclear state population control with potential applications in nuclear physics.

Contribution

It introduces a method to control the cooperative decay in nuclear ensembles using x-ray light and magnetic fields, advancing nuclear pumping techniques.

Findings

Cooperative excitation significantly modifies nuclear dynamics.

Coherent control of decay enhances pumping efficiency.

Feasible implementations with M"ossbauer systems like $^{57} ext{Fe}$ are proposed.

Abstract

Coherent control of nuclear pumping in a three level system driven by x-ray light is investigated. In single nuclei, the pumping performance is determined by the branching ratio of the excited state populated by the x-ray pulse. Our results are based on the observation that in ensembles of nuclei, cooperative excitation and decay leads to a greatly modified nuclear dynamics, which we characterize by a time-dependent cooperative branching ratio. We discuss prospects of steering the x-ray pumping by coherently controlling the cooperative decay. First, we study an ideal case with purely superradiant decay and perfect control of the cooperative emission. A numerical analysis of x-ray pumping in nuclear forward scattering with coherent control of the cooperative decay via externally applied magnetic fields is presented. Next, we provide an extended survey of nuclei suitable for our scheme, and propose proof-of-principle implementations already possible with typical M\"ossbauer nuclear systems such as $^{57}\mathrm{Fe}$. Finally, we discuss the application of such control techniques to the population or depletion of long-lived nuclear states.