Department of Chemical Physics, Lund University, Box 124, Lund SE-21000, Sweden.
J Chem Phys. 2010 May 7;132(17):174508. doi: 10.1063/1.3404402.
The role of weakly chirped pulses (time bandwidth product, DeltanuDeltatau<0.61) on three-pulse photon echo signals has been systematically studied. Pulses with varying chirp were characterized with frequency resolved optical gating (FROG) and used to measure spectrally resolved three-pulse photon echoes of a dye in solution. The weakly chirped pulses give rise to markedly different echo signals for population times below approximately 100 fs. The chirped pulses can decrease or enhance spectral signatures of an excited state absorption transition in the echo signal. Furthermore, the observed dephasing dynamics depend on the phase of the electric fields. Simulations based on a three-level model and the electric fields retrieved from the FROG traces give a good agreement for photon echo experiments with both transform limited and chirped pulses. The simulations also allow for a numerical investigation of effects of chirp in two-dimensional spectroscopy. For a two-level system, the chirped pulses result in nonelliptical two-dimensional spectra that can erroneously be interpreted as spectral heterogeneity with frequency dependent dephasing dynamics. Furthermore, chirped pulses can give rise to "false" cross peaks when strong vibrational modes are involved in the system-bath interaction.
我们系统地研究了弱啁啾脉冲（时带宽积，ΔνΔτ<0.61）对三脉冲光子回波信号的作用。用频率分辨光门（FROG）对具有不同啁啾的脉冲进行了表征，并用于测量溶液中染料的光谱分辨三脉冲光子回波。对于大约 100fs 以下的群体时间，弱啁啾脉冲会产生明显不同的回波信号。啁啾脉冲可以降低或增强回波信号中激发态吸收跃迁的光谱特征。此外，观察到的退相动力学取决于电场的相位。基于三能级模型和从 FROG 轨迹中获取的电场进行的模拟，对于具有变换限制和啁啾脉冲的光子回波实验，均给出了很好的吻合。模拟还允许对二维光谱中的啁啾效应进行数值研究。对于二能级系统，啁啾脉冲会导致非椭圆二维光谱，当系统-浴相互作用中涉及强振动模式时，这些光谱可能会错误地被解释为具有频率相关退相动力学的光谱异质性。此外，当涉及强振动模式时，啁啾脉冲会产生“虚假”交叉峰。
