Enhancement and de-enhancement effects in vibrational resonance Raman optical activity

In this study, we investigate interference between several excited electronic states in resonance enhanced vibrational Raman optical activity (RROA) spectra. A gradient Franck-Condon model for the excited-state potential energy surface is applied in order to include vibronic effects in the description of the RROA intensities. Both sum-over-states and time-dependent expressions for the RROA intensities in case of close-lying excited states are given. As an example, we compare the calculated RROA and resonance Raman spectra of (S)-(+)-naproxen-OCD3 to the experimental ones. Subsequently, we examine the excitation profiles of (S)-(+)-naproxen and study the vibration at 1611 cm(-1) in more detail in order to demonstrate how the consideration of a second excited electronic state can lead to significant changes in the RROA intensities.