Observation of lithium dimers in laser produced plume by cavity ring-down spectroscopy

Laser ablation of solid lithium with 308 nm excimer laser is performed. Cavity ring-down absorption spectroscopy is used to detect atoms and molecules in the plume. They are observed at given distances from the target depending on different time delay from vaporization and observation window width. Large ratio of dimer to atom densities is observed compared to the thermalized vapor. Fast dimers appear with rovibrational temperatures about 175 K. Slow dimers exhibit non-Boltzmann rovibrational distribution in which large rotational numbers are preferred.