Knowledge Bank

A Zeeman modulated microwave spectrometer, designed specifically for K-band rotational studies of gaseous free radicals and transient molecular species, and using a Fabry-Perot type resonator as the absorption cell, will be described. The sensitivity of the system is found to be comparable to that of the most sensitive waveguide-cell spectrometers. The location of previously assigned spectra of OH and $NO2$ radicals has been successfully made with the system. The utility of the system as a search spectrometer for free radicals has been substantiated by locating previously unreported spectra for the $NO2$ molecule and for the $NF2$ (difluoroamino) free radical.