We simulate the two-dimensional electronic spectra (2DES) of the light-harvesting complex II (LHCII) at room temperature by combining the hierarchical equations of motion method and the equation-of-motion phase-matching approach. The laser-excited population dynamics of LHCII is also calculated to help understanding the 2DES. Three different excitation schemes are studied, including (1) only the chlorophyll (Chl) b Q states of LHCII are excited, (2) only the Chl a Q states are excited, and (3) both the Chl b and Chl a states are excited. The energy transfer pathways and time scales revealed from the 2DES in schemes (1) and (2) agree with the recent experimental studies for the Chl b to Chl a energy transfer and the excitation energy relaxation process within the Chl a manifold. We also propose a different way to better present the signals of bottleneck states by investigating the diagonal peaks of the 2DES in scheme (3).

No abstract

The difference between the excited-and ground-state vibrational wavepackets remains to be fully explored when multiple vibrational modes are coherently excited simultaneously by femtosecond pulses. In this work, we present a series of one-and two-dimensional electronic spectroscopy for studying multimode wavepackets of oxazine 720 in solution. Fourier transform (FT) maps combined with time− frequency transform (TFT) are employed to unambiguously distinguish the origin of low-frequency vibrational wavepackets, that is, an excitedstate vibrational wavepacket of 586 cm −1 with a dephasing time of 0.7 ps and a ground-state vibrational wavepacket of 595 cm −1 with a dephasing time of 1.3−1.7 ps. We also found the additional low-frequency vibrational wavepackets resulting from the coupling of the 595 cm −1 mode to a series of high-frequency modes centered at 1150 cm −1 via electronic transitions. The combined use of FT maps and TFT analysis allows us to reveal the potential vibrational coupling of wavepackets and offers the possibility of disentangling the coupling between the electronic and vibrational degrees of freedom in condensed-phase systems.