Theoretical vertical excitation energies and simulated UV spectrum are reported for the canonical (amino-oxo) form of cytosine. The calculations were performed by the EOM-CCSD and EOM-CC3 methods with basis sets up to triple-zeta quality. Beyond vertical excitations, the complete vibronic spectrum has been determined the first time, using the linear vibronic coupling (LVC) method. On the basis of the computed data, a critical review of the available experimental information (UV spectra, linear dichroism, Resonance Raman and REMPI measurements) has led to the surprising conclusion that cytosine has only two, rather than four, observable electronic transitions in the UV range up to 60000 cm-1. The result may be of crucial importance for future photochemical studies.
- Ab initio calculations
- DNA damage
- Excited states
- UV/Vis spectroscopy
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry