The influence of solute-solvent interactions on the vibrational energy relaxation dynamics of perylene and substituted perylenes in the first singlet excited-state upon excitation with moderate (<0.4 eV) excess energy has been investigated by monitoring the early narrowing of their fluorescence spectrum. This narrowing was found to occur on timescales ranging from a few hundreds of femtoseconds...

The matrix elements of the XH, rotation-tunneling Hamiltonian are given for basis states with all of the vibrational excitation in a single bond. A basis set of symmetrized rovibrational wave functions is given that are eigenfunctions in the limit in which the local mode tunneling rate is much smaller than the rotational precession rate. Using this basis, it is demonstrated that, in this limit,...