THE INFRARED AND NEAR-INFRARED SPECTRA OF HCC AND DCC TRAPPED IN SOLID NEON

Spectra have been recorded from 700 to 12 000 cm(-1) for HCC and DCC t rapped in solid neon. In this region, which includes not only the grou ndstate absorptions but also all of the absorptions of appreciable int ensity in the highly perturbed A (II)-I-2 state, all of the matrix shi fts are to lower frequencies, and none of them exceeds 30 cm(-1). The ($) over tilde X(OnO) and ($) over tilde X(Onl) progressions of HCC, r ecently reported in the photoelectron spectrum of HCC-, also appear in the infrared spectrum. The spectra of the singly and doubly carbon-13 substituted species of HCC and of doubly carbon-13 substituted DCC ar e presented. Except in a few regions of very strong mixing of energy l evels of the ($) over tilde X and ($) over tilde A states, correlation s of the HCC and DCC bands with their carbon-13 substitution counterpa rts are possible, and the resulting isotopic shift data are useful in assigning the vibronic spectra. Assignments are proposed for a conside rable number of HCC and DCC bands. These assignments are aided by the carbon-13 shift data, by the results of recent ab initio calculations. and, where they are available, by the upper-state symmetries of bands observed in the gas phase. Absorptions of C-2, C-2(-), C-4, HC4, HCCO , and C2H3 isolated in a neon matrix are also identified. (C) 1995 Aca demic Press, Inc.