FAR-INFRARED SPECTROSCOPY OF SHORT-LIVED SPECIES

Detection and characterization of short-lived species, or radicals, have been one of the main targets of high-resolution molecular spectroscopy. These kinetically unstable substances can be produced only in a very small amount under ordinary laboratory measurement conditions, it is essential to increase the sensitivity of the spectrometer and/or to improve the production efficiency of the molecules to be studied. Conventional microwave spectroscopy has taken an approach to raise the operating frequency to far-infrared region, expecting that effective absorption coefficient will increase. Sensitivity of the spectrometer in far-infrared region, or THz frequency region, has greatly improved thanks to succesful development of frequency multiplication techinques. Along with searching for an efficient production method of the short-lived species, many kinds of short-lived species can be possible to observe. Based on this situation, I would like to show several examples of far-infrared spectrosocpy of reactive species such as CH$_{2}$, NH$_{2}$, and CHF$_{2}$