ULTRAVIOLET PRERESONANCE RAMAN-SCATTERING OF BENZENE-DERIVATIVES .2. INTERFERENCE EFFECTS IN THE EXCITATION PROFILES OF THE VIBRONICALLY ACTIVE FUNDAMENTALS

Raman resonance and antiresonance behavior is observed in the ultraviolet preresonance excitation region for the scattering of those vibrations known to be vibronically active in the 1La and 1L b electronic transitions of toluene, m -xylene, and fluorobenzene. These effects are found to be due to the constructive and destructive interferences between scattering contributions derived from the vibronic coupling of the low lying ππ* transitions and transitions in the far-UV region. This behavior is seen to reflect the varying sign of the allowed 1Lb and 1La transition moment among these derivatives. Calculations are performed which show how the allowed transition moment in m-xylene is of opposite sign to that of these two monosubstituted benzenes. © 1979 American Institute of Physics.