Far Infrared Spectroscopy of Molecular Ions and Short-lived Molecules using frequency tunable CW sources

点击翻译按钮获取中文摘要

We installed a microwave power source, a MW frequency standard system, and a dc discharge power supply, and constructed a frequency stabilized <CO_2> laser. The <CO_2> laser and microwave power source combined with another <CO_2> laser which will be home-made in the coming years will be used to generate frequency tunable CW far infrared radiation by using a non-linear element, MIM diode.We constructed a high-sensitivity millimeter and submillimeter spectrometer, using the microwave power source, the frequency standard, the dc discharge power supply, a home made discharge cell, an InSb detector, and a frequency multiplier. The sensitivity of the spectrometer is high enough to study molecular ions, free radicals, and interstellar molecules. The results obtained are summarized below. 1). The microwave spectrum of the NF radical in the electronically excited state <a^1> <DELTA> ( <T_e> = 12000 <cm^(-1)> ) was observed for the first time and its detailed molecular constants were precisely determined. 2).The pure rotational spectra of <HBF^+> , <H_3> <S^+> , and <H_2> <Cl^+> were detected for the first time. <H_3> <S^+> is a key molecualr ion in the chemistry of sulfur-containing interstellar molecules and <H_2> <Cl^+> is also expected to exist in interstellar space. 3). Two members of a new sulfur-containing carbon-chain molecules, CCS and <C_3> S, were detected by laboratory microwave spectroscopy. The detailed molecular constants obtained made us to assign fourteen unidentified interstellar lines observed by 45m radio telescope of Nobeyama Radio Observatory and by 7m telescope of Bell Telephone Laboratory. Particularly four of seven strongest unidentified lines including U45379 were assigned to the transitions of the CCS radical and three to the <C_3> S molecule.