Relativistic and radiative corrections to the Mollow spectrum

The incoherent inelastic part of the resonance fluorescence spectrum of a laser-driven atom is known as the Mollow spectrum [B. R. Mollow, Phys. Rev. 188, 1969 (1969)]. Starting from this level of description, we discuss theoretical foundations of high-precision spectroscopy using the resonance fluorescence light of strongly laser-driven atoms. Specifically, we evaluate the leading relativistic and radiative corrections to the Mollow spectrum, up to the relative orders of ${\left(Z\alpha \right)}^2$ and $\alpha {\left(Z\alpha \right)}^2$, respectively, and Bloch-Siegert shifts as well as stimulated radiative corrections involving off-resonant virtual states. Complete results are provided for the hydrogen $1S\text{−}2P_{1∕2}$ and $1S\text{−}2P_{3∕2}$ transitions; these include all relevant correction terms up to the specified order of approximation and could directly be compared to experimental data. As an application, the outcome of such experiments would allow for a sensitive test of the validity of the dressed-state basis as the natural description of the combined atom-laser system.

Figure 1

Diagrammatic representation of a radiative self-energy correction to the laser-dressed atomic state. The double line corresponds to the electron bound by the nuclear Coulomb field. The jagged line denotes the additional dressing of the bound electron by the (strong) laser field. The self-energy of a laser-dressed Coulomb-bound electron is a quantum-field theoretic problem in the presence of two classical background fields.