Physical Review A
Two-dimensional optical spectroscopy by periodic excitation of sublevel coherence with sub-Doppler resolution
Gerhard Wäckerle, Stephan Appelt, M. Mehring
Abstract
The response of ground-state spin coherence to narrow-band periodic optical excitation is studied theoretically and experimentally. The dependence of the induced oscillating magnetization on the transverse magnetic field and on the frequency of the laser radiation is calculated for a four-level model system from a Bloch-type equation, yielding a two-dimensional resonance line. The application of this two-dimensional high-resolution Zeeman and optical spectroscopy is demonstrated experimentally in the case of the ${\mathit{D}}_{1}$ line of atomic rubidium vapor. Resolution in the kilohertz range is achieved, which allows clear spectral separation of the two isotopes $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$, showing overlapping lines in the conventional optical absorption spectrum.