This figure shows the interstellar "XCN" infrared absorption feature seen in the direction of the protostar W33A and compares it to the spectra of an irradiated interstellar ice analog residue. Click on the figure for a larger image. Our work has shown that the interstellar band can be reproduced extremely well by the UV irradiation on mixed-molecular ices that contain photolytic C and N. This, and the positon of the band, suggest that the carrier of the "XCN" band is a nitrile or isonitrile, i.e., it contains a N atom triply bonded to a C atom. This feature is also seen in our interstellar/cometary ice analogs from which HMT was extracted at room temperature.

The figure also compares the interstellar "XCN" feature to that of an irradiated sample of hexamethyenetetramine (HMT; C₆H₁₂N₄), which also reproduces the feature. This is one of several observations that suggest that HMT and the carrier of the "XCN" band may be related.

For more detailed information on our laboratory work on our work concerning the "XCN" band, see:

Bernstein, M. P., Sandford, S. A., & Allamandola, L. J. (1997). The Infrared Spectra of Nitriles and Related Compounds Frozen in Ar and H₂O. Astrophys. J. 476, 932-942.

Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Chang, S., & Scharberg, M. A. (1995). Organic Compounds Produced by Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol. Astrophys. J. 454, 327-344.

Bernstein, M. P., Sandford, S. A., Allamandola, L. J., & Chang, S. (1994). Infrared Spectrum of Matrix-Isolated Hexamethylenetetramine in Ar and H₂O at Cryogenic Temperatures. J. Phys. Chem. 98, 12206-12210.

Tegler, S. C., Weintraub, D. A., Allamandola, L. J., Sandford, S. A., Rettig, T. W., & Campins, H. (1993). Detection of the 2165 cm^-1 (4.619 µm) XCN Band in the Spectrum of L1551 IRS 5. Astrophys. J. 411, 260-265.