Collisional Excitation and Weak Maser Action of Interstellar Methanimine

Abstract

The inelastic cross sections and rate coefficients for the rotational excitation of methanimine (CH${}_2$NH) by cold H${}_2$ have been determined quantum mechanically based on a new highly correlated five-dimensional potential energy surface. This surface was fitted to more than 60 000 ab initio points with a root mean square error of $\sim$ 1-2 cm${}^{-1}$ in the region of the potential well whose depth is -374.0 cm${}^{-1}$. The rotationally inelastic rate coefficients have been combined with spectroscopic data to generate the non-equilibrium spectrum of CH${}_2$NH towards the interstellar molecular cloud Sgr~B2(N). The transition $1_{10}\to 1_{11}$ at 5.29 GHz is found to be inverted and the predicted weak maser emission spectrum is in excellent agreement with new observations performed with the 100-meter Green Bank Telescope.

16 pages, 4 figures

References in corpus (3)

• Survey Observations of a Possible Glycine Precursor, Methanimine (CH${}_2$NH)
• An ATCA Survey of Sagittarius~B2 at 7~mm: Chemical Complexity Meets Broadband Interferometry
• Upper limits to interstellar NH+ and para-NH2- abundances. Herschel-HIFI observations towards Sgr B2 (M) and G10.6-0.4 (W31C)

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