FTIR Spectroscopy and Density Functional Theory of the 1474 cm$^{-1}$ Absorption in C$_{n}$ Carbon Cluster Spectra

The identification of the infrared frequencies of carbon clusters is significant for astrophysical and material science research. By using FTIR spectroscopy, density functional theory, and argon matrix trapping numerous C$_{n}$ carbon clusters have been observed in the Nd:YAG laser ablation products trapped in solid argon. An unidentified absorption at 1474 cm$^{-1}$ has been observed in our experiments, and $^{13}$C isotopic shift measurements and DFT calculations have been performed to test potential C$_{n}$ candidates for the carrier of the band. The number and relative intensities of the isotopic shifts suggest a molecule consisting of 4 or 6 atoms. Simulated $^{13}$C shift spectra have been calculated for a variety of 4- and 6-member C$_{n}$ structure$_{ }$using the B3LYP functional and ccPVDZ basis set. Potential sources of the 1473 cm$^{-1}$ band will be discussed.