Direct observation of the femtosecond nonradiative dynamics of azulene in a molecular beam: The anomalous behavior in the isolated molecule

Using femtosecond-resolved mass spectrometry in a molecular beam, we report real-time observation of the nonradiative, anomalous dynamics of azulene. We studied both S-2 and S-1 state dynamics. The motion of the wave packet in S-1 involves two time scales, a dephasing time of less than 100 fs and a 900+/-100 fs internal conversion. We discuss the dynamical picture in relation to the molecular structures and the conical intersection, and we compare with theory. (C) 1999 American Institute of Physics. [S0021-9606(99)02720-8].