State filtering by a bath: up to 24 mode numerically exact wavepacket propagations

Numerically exact wavepacket calculations have been performed on a subsystem coupled to an explicitly treated finite bath, using recently developed techniques within the framework of the multiconfiguration time-dependent Hartree (MCTDH) method. The subsystem of 4 nuclear modes and 2 interacting electronic states was coupled to a bath of up to 20 harmonic oscillators. The results show that the presence of the bath leads to a clear, long-lived structure in the autocorrelation function. Surprisingly, this regular structure becomes more dominant as the number of bath modes is increased, and is due to excited states above the conical intersection. Furthermore, it lasts for times much longer than that of the inter-state population relaxation process.