Observation of restricted IVR in large molecules: Quasi-periodic behavior, phase-shifted and non-phase-shifted quantum beats

The concept of phase-shifted quantum beats in large molecules is developed. Measurements are reported for jet-cooled anthracene excited by a 15 ps pulse to S_1 + 1420 cm^(−1). The results represent the direct observation, in the time domain, of vibrational energy flow within specific sets of modes in the molecule. The importance of the results to intramolecular vibrational-energy redistribution (IVR) and quasi-periodic behavior is discussed