Vibrational and Electronic Spectroscopy of the Fluorene Cation

Abstract

The fluorene cations, C13H10+ and C13D10+, have been formed by both electron impact ionization and vacuum ultraviolet photoionization, deposited in an argon matrix at 12K and studied via Fourier transform infrared and ultraviolet/visible absorption spectroscopy. Harmonic vibrational frequencies have been calculated using density functional theory (B3LYP/6-31G(d,p)) and vibrational band assignments made. Good agreement is found. Dramatic differences have been observed in the infrared band intensities of the cations compared to their neutral parents. Two excited electronic band systems have been observed and compared with previous photoelectron spectroscopic results. New calculations of the fluorene cation excited states have been performed using configuration interaction singles (CIS), CIS with a doubles correlation correction (CIS(D)), time-dependent Hartree−Fock (TDHF), and time-dependent density functional theory (TDDFT) with SVWN, BLYP, and B3LYP functionals. Theoretically, 12 low-lying excited states ...