Construction of a High-Resolution Terahertz Cavity Ringdown Spectrometer

Three new far-IR observatories, the Herschel Space Observatory, the Atacama Large Millimeter Array, and the SOFIA observatory, 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-infrared, or terahertz (THz), spectral window. However, the corresponding laboratory spectra needed to interpret these observations remain largely unavailable. Acquisition of these spectra is hindered by the limitations of current-generation laboratory spectrometers. Spectral data for transient species that are thought to play important roles in interstellar chemistry, such as ions and radicals, 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 (CRDS) 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-CRDS system for the study of transient astrochemical molecules.