Hyperfine structure in theXΣ2state of CaCl measured with microwave-optical polarization spectroscopy

Abstract

Microwave-optical polarization spectroscopy allowed the study of transitions between low-lying rotational states in the ${}_{}{}^2{}_{}{}^{}\Sigma$ ground state of CaCl which conventional microwave absorption and microwave-optical double-resonance (MODR) techniques would have failed to detect. In the $N=1\mathrm{}\leftarrow 0$ transition the hyperfine structure could be completely resolved. Linewidths obtained with the new method were between 1 and 2 MHz, an improvement of an order of magnitude compared to MODR.