Probing ultrafast internal conversion through conical intersection via time-energy map of photoelectron angular anisotropy

The ultrafast photoelectron imaging technique was used to perform ultrafast internal conversion of [S.sub.2] to [S.sub.1] of pyrazine through a conical intersection of the potential energy surfaces. The two-dimensional time-energy map of the photoelectron angular anisotropy revealed a clear signature of the internal conversion (the color change of green-orange-green in the horizontal direction).