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Title:Spectrometer Using Superconductor Mixer Receiver (sumire) For Microwave Spectroscopy Of Molecules In Astronomical Interests
Author(s):Sakai, Nami
Contributor(s):Tamanai, Akemi; Watanabe, Yoshimasa
Abstract:In radio astronomy, accurate rest frequencies of molecular transitions are indispensable for secure identification of molecular species and accurate analyses of Doppler shifts caused by motions of target sources. In observations, we have seriously realized the importance of the accurate rest frequencies of molecular transitions. For rare isotopic species lines and weak vibrational satellite lines, the situation is more serious. To overcome such a situation, an emission-type millimeter-wave spectrometer utilizing state-of-the-art radio-astronomical technologies is developed. The spectrometer is equipped with a 200 cm glass cylinder cell, a two sideband (2SB) Superconductor-Insulator-Superconductor (SIS) receiver in the 215-265 GHz band, and wide-band auto-correlation digital spectrometers. By using the four 2.5 GHz digital spectrometers, a total instantaneous bandwidth of the 2SB SIS receiver of 8 GHz can be covered with a frequency resolution of 88.5 kHz. This wide bandwidth allows us to measure relative intensities of lines which fall into the 8 GHz range. Spectroscopic measurements of HDO, CH$_3$CN, and CH$_3$OH are carried out in the 230 GHz band so as to examine frequency accuracy, stability, and sensitivity, as well as intensity calibration accuracy of our system. We confirm that the frequency accuracy for lines detected with a sufficient signal-to-noise ratio is better than 1 kHz, when the high-resolution spectrometer having a channel resolution of 17.7 kHz is used. Following this successive development of the spectrometer, we are measuring spectral lines of various isotopic species of molecules in astronomical interests.
Issue Date:2021-06-24
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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