HIGHLY UNSATURATED-HYDROCARBONS AS POTENTIAL CARRIERS OF SOME DIFFUSE INTERSTELLAR BANDS

Absorption spectra of highly unsaturated hydrocarbons were obtained in 5 K neon matrices by means of an approach which combines mass-selection and matrix isolation techniques. Mass-selected carbon species, C(n)H(m)-, with n = 14 or 16 and m < 3, were condensed with neon to form a matrix at 5 K using concomitant mercury lamp irradiation. In the 600-860 nm region, many of the observed electronic absorption bands lie close to known diffuse interstellar bands (DIBs); the matches are especially striking above 700 nm. For the hitherto studied species, comprised of 6 to 16 carbons, 17 bands above 600 nm ''coincide'' with DIBs within +/- 36 cm-1, the criterion chosen to accommodate a possible neon matrix-gas phase shift. The observation of the first members of vibrational progressions for some of the bands with corresponding DIBs allows predictions for astrophysical studies to test this proposal.