ASTROCHEMISTRY

Anions in Space

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Science  08 Dec 2006:
Vol. 314, Issue 5805, pp. 1517
DOI: 10.1126/science.314.5805.1517b

Although more than 100 neutral molecules and 14 molecular cations have been identified in space, polyatomic anions have eluded detection. Most detection efforts have focused on small anions for which well-resolved spectra have been measured in the laboratory.

McCarthy et al. report rotational spectra for the comparatively large linear triynyl anion C6H. In the millimeter band, absorption spectra were acquired from samples generated by dc discharge of acetylene at low pressures. In the centimeter band, Fourier-transform microwave spectra were obtained using a molecular-beam source. Spectral shifts for the deuterated isotopomer helped to confirm the assignment. These spectra proved to be an excellent match to a harmonic series observed more than a decade ago in the infrared carbon star IRC +10216 in Leo, as well as to features observed in the Taurus molecular cloud TMC-1. The large size of this anion likely helps it to retain its excess electron despite high fluxes of ionizing ultraviolet radiation in space. — PDS

Astrophys. J. 652, L141 (2006).

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