Raman and fluorescence spectra of size-selected, matrix-isolated C₁₄ and C₁₈ neutral carbon clusters

The surface plasmon polariton-enhanced Raman spectra of size-selected, matrix-isolated C₁₄ neutral clusters are presented along with the calculated vibrational frequencies for the ring and linear chain isomers. The Raman spectra show resonance enhancement over a range of excitation wavelengths from 457.9 to 514.5 nm. The measured vibrational spectra are most consistent with the linear chain isomer. In addition, fluorescence spectra of neutral, mass-selected C_n (n = 14 and 18) clusters are presented. The isolated C₁₄ clusters display strong fluorescence with vibrational structure between 520 and 700 nm. The origins of the observed fluorescence for both C₁₄ and C₁₈ are investigated using the ZINDO/S, CIS, and TD-B3LYP methods.