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, Lucy M Ziurys, H. S P Müller

Research output: Contribution to journalArticle

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Abstract

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
Volume673
Issue number2
DOIs
StatePublished - Feb 1 2008

Fingerprint

rotational spectra
Fourier transform
torsion
atomic absorption spectroscopy
millimeter waves
antenna
hydrolysis
Stardust Mission
observatory
frequency ranges
perturbation
radio
microwaves
acid
gas
energy
molecules
observatories
amines
absorption spectroscopy

Keywords

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

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

The rotational spectrum of anti-ethylamine (CH3CH 2NH2) from 10 to 270 GHz : A laboratory study and astronomical search in SGR B2(N). / Apponi, A. J.; Sun, M.; Halfen, D. T.; Ziurys, Lucy M; Müller, H. S P.

In: Astrophysical Journal, Vol. 673, No. 2, 01.02.2008, p. 1240-1248.

Research output: Contribution to journalArticle

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abstract = "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.",
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