Characterization of the Quasi-Stationary State of an Impurity Driven by Monochromatic Light II - Microscopic Foundations

TL;DR

This paper rigorously derives the microscopic dynamics of an impurity atom driven by monochromatic light interacting with a thermal electron reservoir, establishing a fundamental basis for optical pumping in laser physics.

Contribution

It provides a rigorous quantum mechanical derivation of the effective dynamics of an atom interacting with light and electrons, connecting full and reduced models from first principles.

Findings

Established the relation between full and effective atom dynamics.

Developed a microscopic theory of optical pumping.

Generalized the model to include gauge-invariant interactions.

Abstract

From quantum mechanical first principles only, we rigorously study the time-evolution of a $N$-level atom (impurity) interacting with an external monochromatic light source within an infinite system of free electrons at thermal equilibrium (reservoir). In particular, we establish the relation between the full dynamics of the compound system and the effective dynamics for the $N$-level atom, which is studied in detail in [Bru-de Siqueira Pedra-Westrich, Annales Henri Poincar\'e, 13(6):1305-1370, 2012]. Together with [Bru-de Siqueira Pedra-Westrich, Annales Henri Poincar\'e, 13(6):1305-1370, 2012] the present paper yields a purely microscopic theory of optical pumping in laser physics. The model we consider is general enough to describe gauge invariant atom-reservoir interactions.