HIGHLY UNSATURATED-HYDROCARBONS AS POTENTIAL CARRIERS OF SOME DIFFUSEINTERSTELLAR BANDS

Absorption spectra of highly unsaturated hydrocarbons were obtained in 5 K neon matrices by means of an approach which combines mass-selecti on 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 cl ose to known diffuse interstellar bands (DIBs); the matches are especi ally striking above 700 nm. For the hitherto studied species, comprise d of 6 to 16 carbons, 17 bands above 600 nm ''coincide'' with DIBs wit hin +/- 36 cm-1, the criterion chosen to accommodate a possible neon m atrix-gas phase shift. The observation of the first members of vibrati onal progressions for some of the bands with corresponding DIBs allows predictions for astrophysical studies to test this proposal.