Correlation between nuclear spin ratio of cyclic C3H2 and chemical evolution in TMC-1 cores

Yusuke Morisawa, Mizuho Fushitani, Yoshiyasu Kato, Hiromichi Hoshina, Zenzo Slmizu, Shiori Watanabe, Yuki Miyamoto, Yasuko Kasai, Kentarou Kawaguchi, Takamasa Momose

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12 Citations (Scopus)


The ortho-to-para nuclear spin ratio of cyclopropenylidene (cyclic C 3H2) in TMC-1 cores was investigated using the 45 m radio telescope at Nobeyama Radio Observatory. We have observed four ortho lines (JK,KC = 212-101,312303, 321-312, and 3 30-321) and four para lines (JKaKc = 2 02-111, 211-202,2 20-211, and 322-313) of cyclic C3H2 in six cores in TMC-1. A statistical equilibrium analysis of the observed intensities revealed apparent correlation between the ortho-to-para ratio of cyclic C3H2 and chemical evolution of the molecular cloud; the ortho-to-para ratio in younger cores is less than 2, while that in older cores is close to the statistical ratio of 3. A simple chemical model calculation indicates that the correlation is ascribed to the conservation of nuclear spin angular momenta in chemical reactions relevant to the production, destruction, and reproduction of cyclic C3H 2. Since cyclic C3H2 has been observed in a variety of sources, the ortho-to-para ratio of cyclic C3H2 may be a useful probe of chemical evolution of molecular clouds.

Original languageEnglish
Pages (from-to)954-965
Number of pages12
JournalAstrophysical Journal
Issue number2 I
Publication statusPublished - May 10 2006
Externally publishedYes


  • ISM: abundances
  • ISM: individual (TMC-1)
  • ISM: molecules

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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