ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The structure and excited state dynamics of jet-cooled 9,9′-bianthryl (BA) and its 1:1 van der Waals (vdW) complexes with Ne, Ar, and H2O were studied using rotational coherence spectroscopy (RCS). For a free BA molecule, the magnitude and persistence of the recurrent transient appearing in the time-correlated single photon counting (TCSPC) measurement was found to be dependent on the torsional level of BA, indicating the rotational constant changes with the torsional energy level. The RCS–TCSPC measurement of the BA–Ar and BA–H2O complexes in the S1 state showed no coherent transients. However, the pump–probe time-resolved fluorescence depletion (TRFD) detected the weak J-type transient. Those facts imply the loss of coherence in the BA vdW complexes due to the excited-state dynamics, which coincides with the analysis of the laser-induced fluorescence excitation and dispersed fluorescence spectra. The structure of the ground-state 1:1 BA complex with Ne, Ar, and H2O was determined based on the RCS transients observed in the TRFD measurement with the help of a minimum energy structure calculation using atom–atom pairwise potentials. The rapid dephasing in the excited state was demonstrated by the magic angle TRFD detection near t=0. The dominant dephasing process for the rare-gas complexes is ascribed to intramolecular vibrational energy redistribution (IVR) which is accelerated by significant coupling between the torsional vibration and the low-lying vdW vibrations. IVR process for the H2O complex accompanies the rapid conversion to the charge-transfer state, which is also responsible for the loss of excited-state coherence. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1288518
