Millimeter/submillimeter spectroscopy of PH2CN (X̃1A′) and CH3PH2 (X̃1A′): Probing the complexity of interstellar phosphorus chemistry

D. T. Halfen, D. J. Clouthier, Lucy M Ziurys

Research output: Contribution to journalArticle

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Abstract

Millimeter/submillimeter spectra of PH2CN (X̃1A′) and CH3PH2 (X̃1A′) have been recorded for the first time using direct absorption techniques. This work extends previous measurements of both molecules beyond the 10-50 GHz range. Both species were created in the presence of an AC discharge by the reaction of phosphorus vapor and either cyanogen and hydrogen (PH2CN) or methane (CH3PH2). Twelve rotational transitions of PH2CN were recorded over the region 305-422 GHz for asymmetry components Ka = 0 through 8. For CH3PH2, eight rotational transitions were measured from 210-470 GHz with Ka = 0 through 16; these spectra exhibited greater complexity due to the presence of internal rotation, which splits the Ka = 1, 2, and 3 asymmetry components into A and E states. Combined analyses of the millimeter/submillimeter and previous microwave data were performed for both molecules. For PH2CN, the spectra were fit with a Watson S-reduced asymmetric top Hamiltonian, resulting in more accurate rotational and centrifugal distortion constants. In the case of CH3PH2, an asymmetric top internal-rotation Hamiltonian was employed in the analysis, significantly improving the rotational and torsional parameters over previous microwave estimates. Searches for both molecules were subsequently conducted toward Sgr B2(N), using the 12 m telescope of the Arizona Radio Observatory (ARO). Neither species was identified, with abundance upper limits, relative to H2, of f (PH2CN/H2) < 7.0 × 10-12 and f (CH3PH2/H2) < 8.4 × 10-12. The nitrogen analogs NH2CN and CH3NH2 are therefore more abundant in Sgr B2(N) by factors of >2 and >200, respectively.

Original languageEnglish (US)
Article number36
JournalAstrophysical Journal
Volume796
Issue number1
DOIs
StatePublished - Nov 20 2014

Fingerprint

phosphorus
spectroscopy
chemistry
asymmetry
cyanogen
microwaves
molecules
alternating current
observatories
methane
observatory
telescopes
hydrogen
vapors
radio
estimates
microwave
parameter
analysis

Keywords

  • astrochemistry
  • ISM: molecules
  • line: identification
  • methods: laboratory: molecular
  • molecular data

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Millimeter/submillimeter spectroscopy of PH2CN (X̃1A′) and CH3PH2 (X̃1A′) : Probing the complexity of interstellar phosphorus chemistry. / Halfen, D. T.; Clouthier, D. J.; Ziurys, Lucy M.

In: Astrophysical Journal, Vol. 796, No. 1, 36, 20.11.2014.

Research output: Contribution to journalArticle

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abstract = "Millimeter/submillimeter spectra of PH2CN (X̃1A′) and CH3PH2 (X̃1A′) have been recorded for the first time using direct absorption techniques. This work extends previous measurements of both molecules beyond the 10-50 GHz range. Both species were created in the presence of an AC discharge by the reaction of phosphorus vapor and either cyanogen and hydrogen (PH2CN) or methane (CH3PH2). Twelve rotational transitions of PH2CN were recorded over the region 305-422 GHz for asymmetry components Ka = 0 through 8. For CH3PH2, eight rotational transitions were measured from 210-470 GHz with Ka = 0 through 16; these spectra exhibited greater complexity due to the presence of internal rotation, which splits the Ka = 1, 2, and 3 asymmetry components into A and E states. Combined analyses of the millimeter/submillimeter and previous microwave data were performed for both molecules. For PH2CN, the spectra were fit with a Watson S-reduced asymmetric top Hamiltonian, resulting in more accurate rotational and centrifugal distortion constants. In the case of CH3PH2, an asymmetric top internal-rotation Hamiltonian was employed in the analysis, significantly improving the rotational and torsional parameters over previous microwave estimates. Searches for both molecules were subsequently conducted toward Sgr B2(N), using the 12 m telescope of the Arizona Radio Observatory (ARO). Neither species was identified, with abundance upper limits, relative to H2, of f (PH2CN/H2) < 7.0 × 10-12 and f (CH3PH2/H2) < 8.4 × 10-12. The nitrogen analogs NH2CN and CH3NH2 are therefore more abundant in Sgr B2(N) by factors of >2 and >200, respectively.",
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