Selective Laser-Induced Oxidation of Carbon Chain Molecules in Cryogenic Matrices

We have tested and applied a laser-induced oxidation method for identifying IR-absorptions of those carbon molecules which have known UV/VIS absorptions. For this purpose we trapped the molecules of carbon vapor in non-inert matrices(O2, Ar-O2). Upon matrix annealing, molecular growth took place leading to a mixture of linear carbon species up to C17. The output of an excimer-dye laser was employed to photo-bleach selectively the strong UV/VIS absorptions of these trapped carbon molecules. Correlations of the changes in IR and UV/VIS spectra were observed. After successful tests performed on C9, C11, C13 for which the UV/VIS as well as the IR absorptions are known we applied the method to the C15 molecule for which the UV/VIS absorption is at around 450 nm but the IR absorptions are unknown. In the course of this research we found that the 1819, 1816 cm^-1 pattern of absorptions in an O2-matrix (1818 cm^-1 in an Ar-matrix) can be assigned to the most intense IR-active C13 stretching mode. The pattern of absorption lines at 1721, 1714, 1707 cm^-1 and 1695 cm^-1 can be assigned as site peaks of C15 in an O2-matrix (1713, 1700, 1695 cm^-1 in an Ar-O2-matrix). To obtain information about infrared absorptions of carbon chain oxides of the type CnO and OCnO, oxygen matrices with replaced ^16O -> ^18O isotopes were applied. There we found that two absorptions at 1803 and 1844 cm^-1 in an Ar-matrix (1800 and 1840 cm^-1 in O2) belong to oxides of a carbon chain rather than to a pure carbon species. The absorption at 2180 cm^-1 in an O2-matrix was assigned to the C6O2 molecule. Our data revise some of the assignments existing in the literature.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2004

Author dc:creator

• Strelnikov, Dmitry

Contributors dc:contributor

• Wolfgang (Prof. Dr.), Krätschmer

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/5230

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:5230