Canonical interstellar spacing

Any hydrogenated candidate for the unknown IR emission must exhibit sufficient stability to the harsh conditions of the interstellar medium, including bombardment by particles and ultraviolet and gamma radiation. Equally important, for a species to be considered a viable candidate, its spectra must reproduce two important characteristics found in most diffuse medium spectra. These are (a) that the 1,300 cm-1 band be more intense than the 880 cm-1 band (Williams 1996), and (b) that the spacing between it and the next main emission feature match the canonical interstellar spacing of 300 cm-1 (Hudgins and Allamandola 1999). 

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