On the interaction of a single-photon wave packet with an excited atom

TL;DR

This paper investigates how a single-photon wave packet interacts with an excited atom, revealing effects on atomic transition dynamics and the emitted radiation spectrum using semiclassical and quantum models.

Contribution

It provides a detailed analysis of the interaction dynamics and spectrum modifications, highlighting the influence of incoming photons on atomic state transitions.

Findings

The final field state lacks doubly occupied modes.

Photon interaction can accelerate, decelerate, or reverse atomic transitions.

Emission spectrum is close to the sum of incoming photon spectrum and natural line shape.

Abstract

The interaction of a single-photon wave packet with an initially excited two-level atom in free space is studied in semiclassical and quantum approaches. It is shown that the final state of the field does not contain doubly occupied modes. The process of the atom's transition to the ground state may be accelerated, decelerated or even reversed by the incoming photon, depending on parameters. The spectrum of emitted radiation is close to the sum of the spectrum of the incoming single-photon wave packet and the natural line shape, with small and complicated deviations.