Gdor Itay, Ghosh Tufan, Lioubashevski Oleg, Ruhman Sanford
Institute of Chemistry, The Hebrew University , Jerusalem 9190401, Israel.
J Phys Chem Lett. 2017 Apr 20;8(8):1920-1924. doi: 10.1021/acs.jpclett.7b00559. Epub 2017 Apr 14.
Impulsive Raman excitation in neat organic liquids far from resonance is followed using chirped broad-band supercontinuum probe pulses. Spectral modulations due to impulsively induced coherent vibrations vary in intensity 10-fold as a function of the probe's linear chirp. Simulations clarify why the vibrational signature is maximized for a group delay dispersion (GDD) in reduced units of ν = 0.5 while a probe GDD of twice that quenches the same spectral modulations. Accordingly, recent claims that chirped white-light probe pulses provide equivalent information on material response to their compressed analogues must be taken with caution. In particular, interactions that induce spectral shifts in the probe depend crucially on the arrival chronology of the continuum colors. On one hand, this presents limitations to application of chirped continuum radiation as-is in pump-probe experiments. It also presents the opportunity for using this dependence to control the relative amplitude of nonresonant interactions in pump-probe signals such as that of solvent vibrations.
利用啁啾宽带超连续谱探测脉冲跟踪远离共振的纯有机液体中的脉冲拉曼激发。由脉冲诱导的相干振动引起的光谱调制强度随探测光的线性啁啾变化10倍。模拟结果阐明了为什么在约化单位ν = 0.5时，群延迟色散（GDD）使振动信号最大化，而两倍于此的探测光GDD会抑制相同的光谱调制。因此，对于最近声称啁啾白光探测脉冲能提供与其压缩类似物相同的材料响应信息这一说法，必须谨慎对待。特别是，在探测光中引起光谱位移的相互作用关键取决于连续谱颜色的到达时间顺序。一方面，这给直接在泵浦 - 探测实验中应用啁啾连续谱辐射带来了限制。它也提供了利用这种依赖性来控制泵浦 - 探测信号中非共振相互作用的相对幅度的机会，比如溶剂振动的信号。
