Construction of a High-Resolution Terahertz Cavity Ringdown Spectrometer

Two NASA far-infrared observatories, the Herschel Space Observatory and the Stratospheric Observatory for Infrared Astronomy (SOFIA), have undertaken their science missions in the past year. These observatories are set to provide an unprecedented amount of astronomical data in the relatively unexplored far- IR, or terahertz (THz), spectral window. However, the corresponding laboratory spectra needed to interpret these observations remain largely unavailable. Acquisition of such spectra is hindered by the limitations of current-generation laboratory spectrometers at these frequencies. Spectral data for transient species that are thought to play important roles in interstellar chemistry are particularly difficult to acquire without a high-sensitivity, high-resolution spectroscopic technique that goes beyond the standard direct absorption spectrometer. We are developing a THz cavity ringdown spectrometer coupled with a supersonic expansion to aid in the laboratory characterization of unstable molecules that are of astronomical importance. We will report on the performance of our benchtop prototype instrument, as well as our progress toward development of a full THz cavity ringdown spectroscopy (Thz-CRDS) system for the study of transient astrochemical molecules.