High Resolution Laser Spectroscopy of Small Molecules and Clusters

The combination of high resolution laser spectroscopy in collimated cold molecular beams with massselective detection allows investigations of rotationally resolved molecular spectra of selected molecularspecies in the presence of molecules with overlapping absorption spectra. This is illustrated by someexamples, such as the isotope selective spectroscopy of Ag 2 –dimers or the sub-Doppler spectroscopy ofNa 3 in supersonic beam with a broad mass distribution of different clusters. Time resolved laserspectroscopy of excited states of alkali molecules, perturbed by bound dark states or by repulsive states,yields information about singlet–triplet mixing and predissociation rates.