Near-infrared diode laser spectroscopy of free radicals

Spectroscopic results on the radicals HCSi, CCO, and FeC obtained by studying in detail energy level structures using 0.8 microm diode laser system are reported. Of these radicals, the CCO radical was investigated mainly using Fabry-Perot type diode lasers with inconvenient mode gaps in the early stage of our near-infrared diode laser spectroscopic study of free radicals, and on the other hand, the FeC and HCSi radicals were studied using an external cavity diode laser. For the FeC radical, which is an interesting radical composed of an iron atom having 3d electrons, information on spin-orbit interaction between the triplet electronic ground state and a low-lying singlet electronic excited state is reported somewhat in detail. For the HCSi and CCO radicals, spectral particularities produced by a Renner-Teller interaction and a spin-orbit interaction are described for their high-resolution spectroscopic interest.