The millimeter-wave spectrum of CaH (X2Σ+)

W. L. Barclay, M. A. Anderson, L. M. Ziurys

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23 Scopus citations


The millimeter-wave spectrum of the CaH and CaD radicals (X2Σ+) has been observed in the laboratory via direct absorption spectroscopy. The species were generated by the reaction of calcium vapor, produced in a Broida-type oven, with hydrogen atoms created in a microwave discharge. The six hyperfine components of the N = 0 → 1 rotational transition of CaH near 254 GHz were resolved and their frequencies determined to an accuracy of ± 100 kHz. The main hyperfine lines originating in the N = 0 → 1, 1 → 2, and 2 → 3 rotational transitions of CaD were also detected. Spectroscopic constants were determined for both radicals from a nonlinear least squares fit to the data, using a 2Σ Hamiltonian. These measurements constitute the first laboratory observation of CaH at high spectral resolution, and are essential to the detection of this radical in interstellar space.

Original languageEnglish (US)
Pages (from-to)L65-L67
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - 1993


  • ISM: Molecules
  • Line: Identification
  • Molecular data

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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