The rotational spectrum of anti-ethylamine (CH3CH 2NH2) from 10 to 270 GHz: A laboratory study and astronomical search in SGR B2(N)

A. J. Apponi, M. Sun, D. T. Halfen, L. M. Ziurys, H. S.P. Müller

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11 Scopus citations


The pure rotational spectrum of the lowest energy (anti-) conformer of ethylamine (CH3CH2NH3) has been measured in the frequency range of 10-270 GHz. The spectrum was recorded using both millimeter-wave absorption spectroscopy and Fourier transform microwave (FTMW) techniques. Ten rotational transitions of this molecule were recorded in the frequency range of 10-40 GHz using FTMW methods, resulting in the assignment of 53 quadrupoleresolved hyperfine lines; in the millimeter-wave region (48-270 GHz), nearly 600 transitions were assigned to the ground (anti-) state. The amine group in CH3CH2NH2 undergoes inversion, resulting in a doubling that is frequently small and most apparent in the low-frequency K-doubling transitions. In addition, seemingly random rotational levels of this molecule were found to be significantly perturbed. The cause of these perturbations is presently uncertain, but torsion-rotation interactions with the higher lying gauche conformers seem to be a likely explanation. An astronomical search was conducted for ethylamine toward Sgr B2(N) using the Kitt Peak 12 m antenna and the Sub-Millimeter Telescope (SMT) of the Arizona Radio Observatory. Frequencies of 70 favorable rotational transitions were observed in this search, which covered the range 68-263 GHz. Ethylamine was not conclusively detected in Sgr B2(N), with an upper limit to the column density of (1-8) × 1013 cm with/(CH3CH2NH 2/H2) ∼ (0.3-3) × 1011, assuming a rotational temperature of 50-220 K. These observations indicate a gas-phase CH3 CH2NH2/CH3NH2 ratio of <0.0010.01, in contrast to the nearly equal ratio suggested by the acid hydrolysis of cometary solids from the Stardust mission.

Original languageEnglish (US)
Pages (from-to)1240-1248
Number of pages9
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 1 2008


  • Astrobiology
  • Astrochemistry
  • ISM: abundances
  • ISM: individual (Sagittarius B2)
  • ISM: molecules
  • Line: identification
  • Methods: laboratory

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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