Millimeter-wave Spectrum of 2-propanimine

By Keith Cowing
Status Report
February 1, 2023
Filed under , , ,
Millimeter-wave Spectrum of 2-propanimine
2-propanimine ((CH3)2C=NH)

Up to date, only 6 imines have been detected in the interstellar medium. The 3-carbon imine, 2-propanimine ((CH3)2C=NH), is predicted to be the structural isomer with the lowest energy in the C3H7N group, and appears to be a good candidate for astronomical searches.

Unexpectedly, no microwave or millimeter wave spectrum is available for 2-propanimine. In this work, we provide the first high resolution millimeter wave spectrum of 2-propanimine and its analysis. With the guide of this laboratory measurement, we aim to search for 2-propanimine in two molecule-rich sources Sgr B2(N) and IRAS 16293-2422 using observations from the Atacama Large Millimeter/submillimeter Array (ALMA).

Starting from a synthesized sample, we measured the spectrum of 2-propanimine from 50 to 500 GHz, and the ground state lines are successfully assigned and fitted using XIAM and ERHAM programs with the aid of theoretical calculations. The barriers to internal rotation of the two CH3 tops are determined to be 531.956(64) cm−1 and 465.013(26) cm−1.

These data are able to provide reliable prediction of transition frequencies for astronomical search. Although a few line matches exist, no confirmed detection of 2-propanimine has been found in the hot molecular core Sgr B2(N1S) and the Class 0 protostar IRAS 16293B. Upper-limits of its column density have been derived, and indicate that 2-propanimine is at least 18 times less abundant than methanimine in Sgr B2(N1S), and is at most 50-83 % of methanimine in IRAS 16293B.

Luyao Zou, Jean-Claude Guillemin, Arnaud Belloche, Jes K. Jørgensen, Laurent Margulès, Roman A. Motiyenko, Peter Groner

Comments: 14 pages, 10 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2302.00372 [astro-ph.GA] (or arXiv:2302.00372v1 [astro-ph.GA] for this version)
Submission history
From: Luyao Zou
[v1] Wed, 1 Feb 2023 11:01:40 UTC (2,466 KB)
Astrobiology, Astrochemistry

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻