Rotational and rovibrational spectroscopy of CD${}_3$OH with an account of CD${}_3$OH toward IRAS 16293$-$2422

Abstract

Solar-type protostars harbor highly deuterated complex organics. While this degree of deuteration may provide important clues in studying the formation of these species, spectroscopic information on multiply deuterated isotopologs is often insufficient. In particular, searches for triply deuterated methanol, CD${}_3$OH, are hampered by the lack of intensity information from a spectroscopic model. The aim of the present study is to develop such a model of CD${}_3$OH in low-lying torsional states that is sufficiently accurate to facilitate further searches for CD${}_3$OH in space. We performed a new measurement campaign for CD${}_3$OH involving three spectroscopic laboratories that covers the 34 GHz-1.1 THz and the 20-900 cm${}^{-1}$ ranges. The analysis was performed using the torsion-rotation Hamiltonian model based on the rho-axis method. We determined a model that describes the ground and first excited torsional states of CD${}_3$OH, up to quantum numbers $J⩽55$ and $K_a⩽23$, and we derived a line list for radio-astronomical observations. This list is accurate up to at least 1.1 THz and should be sufficient for all types of radio-astronomical searches for this methanol isotopolog. It was used to search for CD${}_3$OH in data from the Protostellar Interferometric Line Survey of IRAS 16293-2422 using ALMA. CD${}_3$OH is securely detected in the data, with a large number of clearly separated and well-reproduced lines. We detected lines belonging to the ground and the first excited torsional states. The derived abundance of CD${}_3$OH relative to non-deuterated isotopolog confirm the significant enhancement of this multiply deuterated variant. This finding is in line with other observations of multiply deuterated complex organic molecules and may serve as an important constraint on their formation models.

Astronomy and Astrophysics, in press. 21 pages, including figures, tables, and appendices; abstract shortened

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Cited by in corpus (9)

• Methanol deuteration in high-mass protostars
• Rotational spectroscopy of mono-deuterated oxirane ($c$-C${}_2$H${}_3$DO) and its detection towards IRAS 16293$-$2422 B
• Implementation of Rare Isotopologues into Machine Learning of the Chemical Inventory of the Solar-Type Protostellar Source IRAS 16293-2422
• A deep search for large complex organic species toward IRAS16293-2422 B at 3 mm with ALMA
• Millimetre and sub-millimetre spectroscopy of doubly deuterated acetaldehyde (CHD2CHO) and first detection towards IRAS 16293-2422
• Rotational spectroscopy of oxirane-\textit{2,2}-$d_2$, $c$-CD${}_2$CH${}_2$O, and its tentative detection toward IRAS 16293$-$2422~B
• Rotational spectroscopy of CH${}_3$OD with a reanalysis of CH${}_3$OD toward IRAS 16293$-$2422
• Investigation of the rotational spectrum of CD${}_3$OD and an astronomical search toward IRAS 16293$-$2422
• Investigation of the rotational spectrum of CH${}_3$${}^{17}$OH and its tentative detection toward Sagittarius B2(N)