Laboratory Measurement of CH₃ ¹⁷OH Transitions in the Frequency Range from 216 to 264 GHz for Astronomical Application

Abstract Methanol is one of the most abundant complex organic molecules in interstellar environments. Molecular lines of its rare isotopologues 12 CH 3 17 OH and 12 CH 3 18 OH therefore play a crucial role in examining the column density of 12 CH 3 16 OH, which serves as a reference for organic molecular chemistry in interstellar clouds. In this study, we have recorded the spectroscopic emission spectrum of 12 CH 3 17 OH in the frequency range between 216 and 264 GHz by making use of an emission-type millimeter and submillimeter spectrometer. We have specifically paid attention to the Q -branch transitions, which are the strongest line series in this frequency region. Among the stable oxygen isotopes, 16 O, 17 O, and 18 O of methanol, only 12 CH 3 17 OH obviously shows line profiles having double and/or triple peaks in low- J transitions, due to the nuclear quadrupole interaction. The newly obtained 12 CH 3 17 OH data will play an important role in facilitating a deeper understanding of the organic chemistry related to star and planet formation. The 12 CH 3 17 OH line data allow us to trace and constrain the isotopic ratio 17 O/ 18 O in methanol, which is efficient to investigate the galactic-scale evolution of elements. In addition, we also assigned some transitions of 13 CH 3 17 OH in the recorded spectrum.