Observation of resonance electronic and non-resonance-enhanced vibrationalnatural Raman optical activity

Natural resonance electronic Raman optical activity (ROA) is observed forthe first time. Coincidently, the first example of vibrational ROA enhanced bylow-lying electronic transition is reported. These new phenomena were measuredusing the rare-earth complex Eu(tfc)3 (+)-tris[3- trifluoroacetyl-D-camphorato]europium(III), where electronic resonance occurs between the 532-nmlaser excitation and the 7F1 5D1 transition of the Eu3+ metal center. Electronic Ramanspectra involve the Raman transitions terminating on the low-lying electronicstates of Eu(tfc)3. The observed vibrational ROA spectra are enhancedrelative to typical ROA spectra by the proximity of vibrational states ofEu(tfc)3 to its low-lying electronic states with significantmagnetic-dipole character, whereas the parent vibrational Raman spectra do notappear to be resonance-enhanced since the 532-nm vibrational Raman spectrum hassimilar relative intensities to the corresponding Raman spectrum measured with1064-nm laser excitation.