Hydrogen-bonded mixtures with varying concentration are a complicated networked system that demands a detection technique with both time and frequency resolutions. Hydrogen-bonded pyridine–water mixtures are studied by a time-frequency resolved coherent Raman spectroscopic technique. Femtosecond broadband dual-pulse excitation and delayed picosecond probing provide sub-picosecond time resolution in the mixtures temporal evolution. For different pyridine concentrations in water, asymmetric blue versus red shifts (relative to pure pyridine spectral peaks) were observed by simultaneously recording both the coherent anti-Stokes and Stokes Raman spectra. Macroscopic coherence dephasing times for the perturbed pyridine ring modes were observed in ranges of 0.9–2.6 ps for both 18 and 10 cm − 1 10\hspace{0.33em}{{\rm{cm}}}^{-1} broad probe pulses. For high pyridine concentrations in water, an additional spectral broadening (or escalated dephasing) for a triangular ring vibrational mode was observed. This can be understood as a result of ultrafast collective emissions from coherently excited ensemble of pairs of pyridine molecules bound to water molecules.

中文翻译：

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氢键合吡啶-水混合物中的超快相移

浓度不同的氢键混合物是一个复杂的网络系统，需要具有时间和频率分辨率的检测技术。通过时频分辨相干拉曼光谱技术研究了氢键合吡啶-水混合物。飞秒宽带双脉冲激励和延迟的皮秒探测可在混合物的时间演化过程中提供亚皮秒的时间分辨率。对于水中不同的吡啶浓度，通过同时记录相干的反斯托克斯光谱和斯托克斯拉曼光谱，观察到不对称的蓝移与红移（相对于纯吡啶光谱峰）。对于18和10 cm-1 10 \ hspace {0.33em} {{\ rm {cm}}} ^ {-1}宽探针，观察到扰动的吡啶环模式的宏观相干移相时间在0.9-2.6 ps的范围内脉冲。对于水中较高的吡啶浓度，观察到三角环振动模式的附加光谱展宽（或逐步移相）。这可以理解为来自与水分子结合的成对吡啶分子的相干激发的集合的超快集体发射的结果。