Flick Johannes, Appel Heiko, Rubio Angel
Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6, D-14195 Berlin-Dahlem, Germany.
Nano-Bio Spectroscopy group, Dpto. Física de Materiales, Universidad del País Vasco , Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Av. Tolosa 72, E-20018 San Sebastián, Spain.
J Chem Theory Comput. 2014 Apr 8;10(4):1665-76. doi: 10.1021/ct4010933. Epub 2014 Mar 24.
We quantify the nonadiabatic contributions to the vibronic sidebands of equilibrium and explicitly time-resolved nonequilibrium photoelectron spectra for a vibronic model system of trans-polyacetylene. Using exact diagonalization, we directly evaluate the sum-over-states expressions for the linear-response photocurrent. We show that spurious peaks appear in the Born-Oppenheimer approximation for the vibronic spectral function, which are not present in the exact spectral function of the system. The effect can be traced back to the factorized nature of the Born-Oppenheimer initial and final photoemission states and also persists when either only initial or final states are replaced by correlated vibronic states. Only when correlated initial and final vibronic states are taken into account are the spurious spectral weights of the Born-Oppenheimer approximation suppressed. In the nonequilibrium case, we illustrate for an initial Franck-Condon excitation and an explicit pump-pulse excitation how the vibronic wavepacket motion of the system can be traced in the time-resolved photoelectron spectra as a function of the pump-probe delay.
我们对反式聚乙炔振动电子模型系统的平衡态和明确的时间分辨非平衡光电子能谱的振动电子边带的非绝热贡献进行了量化。使用精确对角化，我们直接评估了线性响应光电流的态求和表达式。我们表明，在振动电子光谱函数的玻恩-奥本海默近似中会出现虚假峰，而这些峰在系统的精确光谱函数中并不存在。这种效应可以追溯到玻恩-奥本海默初始和最终光发射态的因式分解性质，并且当仅初始态或最终态被相关振动电子态取代时也依然存在。只有当考虑相关的初始和最终振动电子态时，玻恩-奥本海默近似的虚假光谱权重才会被抑制。在非平衡情况下，我们针对初始弗兰克-康登激发和明确的泵浦脉冲激发，说明了如何在时间分辨光电子能谱中追踪系统的振动电子波包运动，该运动是泵浦-探测延迟的函数。
