Lissajous-like wavepacket motion on the two-dimensional adiabatic potential surface in localized excitons

We report the wavepacket motion on the adiabatic potential surface of a self-trapped exciton (STE) in a halogen-bridged mixed-valence Pt complex at 4 K measured by using femtosecond time-resolved luminescence spectroscopy. The observed waveform is complex and differs from the behavior at room temperature. A low-frequency mode, 0.7 THz, was found in addition to the main mode of STE, 3.4 THz. The time evolution of the luminescence intensity was reproduced in terms of a model assuming a Lissajous-figure-like motion of the wavepacket on a two-dimensional adiabatic potential surface.