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Abstract

The long linear carbon molecules C17, C19, C21 and C23 were trapped in cryogenic matrices and investigated by means of absorption spectroscopy. The electronic absorptions of these species in the visible range are known. These molecules were selectively photolysed in oxygen enriched matrices using the laser-induced oxidation method. The selected molecules react with the surrounding oxygen forming oxides thus leading to a decrease of the IR-absorptions of the carbon chains. By this method, several unknown lines in the IR-spectrum could be assigned. The line at 1443 cm-1 was assigned to the IR-absorption of C19 and the line at 1283 cm-1 was assigned to the IR-absorption of C21. The absorptions of oxides of long carbon chains trapped in cryogenic matrices are not known at present. Some of the IR-lines were assigned to the oxides of certain carbon chains using the method of isotopic substitution of matrix material (16O/18O and 12CO/13CO). For the first time it was possible to distinguish monoxides from dioxides. Our data, along with quantum chemical calculations suggest that the positions of the UV/vis- and the IR-absorptions of oxides CnO and CnO2 are located near the absorptions of the parent carbon chains Cn.