Correlation of Infrared and UV-Visible Bands of Matrix-Isolated Carbon Clusters

Article abstract of DOI:10.1021/j100160a030

Carbon clusters, formed by Nd:YAG laser ablation of graphite, have been trapped in solid argon at 12K.Using Fourier transform infrared and UV-visible spectrometers in a crossed beam configuration we have recorded the IR and UV-visible absorption spectra of the same carbon/Ar matrix and followed the growth and decay of bands in both regions as a function of matrix annealing temperature and initial preparation conditions.For the IR bands at 2164 and 1998 cm^-1, previously attributed to linear C5 and nearly linear C8 clusters, respectively, good correlations have been found with the 223- and 308-nm bands, respectively.The 2164-cm^-1/223-nm correlation represents the first positive assignment for an electronic band due to C5.The similarity of the 223-nm band system with the so-called 217.5-nm interstellar hump has been noted and it is suggested that linear C5 clusters may be responsible for this much-discussed feature.Good correlations were also found for the 2039-cm^-1/283-nm, 2039-cm^-1/410-nm, and 1695-cm^-1/586-nm pairs.The 2039-cm^-1/410-nm bands are known to originate from C3, while the species responsible for the 1695-cm^-1/586 nm pair is suggested to be a cyclic cluster of six or more carbons.A prominent UV band system at 247.1 nm has been correlated with an IR band at 2004 cm^-1 and tentatively assigned to linear C9.