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Project Progress

We have made substantial progress in our study of phosphorus chemistry in interstellar space. Following our discovery of PO in the circumstellar ejecta of the Supergiant star VY Canis Majoris by Tenenbaum, Woolf, and Ziurys (2007), we have subsequently found four new phosphorus-bearing compounds in the
outflows from carbon-rich evolved stars: PN, HCP, PH₃, and CCP (Tenenbaum and Ziurys 2008: Halfen, Clouthier and Ziurys 2008; Milam et al. 2008). These discoveries were made using the telescopes of the Arizona Radio Observatory: the Submillimeter Telescope (SMT) and the 12 m. In approximately one year’s time, the inventory of known interstellar phosphorus compounds has therefore increased by 300%.
Particularly intriguing is the detection of the CCP radical, which has phosphorus attached to a C-C bond.
Discovery of this molecule was made possible by spectroscopic measurements conducted in the Ziurys laboratory, in collaboration with Dennis Clouthier (University of Kentucky). A new phosphorus source has been developed for one of the spectrometer systems that has not only enabled the measurements for CCP, but several other possible new interstellar phosphorus-bearing compounds, including PCN, HPS,
and CH₃PH₂. A picture of this new source is shown in Figure 1, and the laboratory spectrum of CCP in Figure 2. In Figure 3, the interstellar spectra from the carbon-rich star IRC+10216 are presented. The interstellar detections indicate that at least 20-40% of the available phosphorus is in the gas-phase in circumstellar material. Phosphorus is thus taking on forms other than the mineral schreibersite, [Fe,Ni]3P. Astronomical searches are currently being conducted for possible new gas-phase phosphorus molecules.
We have also been investigating carbon chemistry in oxygen-rich circumstellar gas. We are finding that carbon chemistry is far more active than previously thought, as evidenced by the detection of HCO⁺ in several of these objects by Pulliam and Ziurys.

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