Ultrafast internal conversion in 4-aminobenzonitrile occurs sequentially along the seam

Abstract

Upon UV light absorption, 4-aminobenzonitrile undergoes an ultrafast radiationless decay process from a charge-transfer state to a locally-excited state. This pathway proceeds through an extended seam of conical intersections between the second- and first-excited singlet electronic states. Quantum dynamics simulations show that planar geometries dominate the earlier times (<20 fs), after which the whole seam becomes explored, as the wavepacket spreads and breathes along both sides of the unstable ridge with respect to the amino-bending coordinate.