We demonstrate a coherent vibrational spectroscopy based on molecular infrared (IR)-active resonance. We apply two femtosecond pulses (one in near-IR and the other in mid-IR) to generate the femtosecond time-resolved IR-resonant third-order sum-frequency signal. The mid-IR pulse is tuned to be resonant with molecular vibrations. This experimental configuration converts the IR light into a visible signal and exhibits high sensitivity to the vibrational mode of the molecule. The technique can be applied to acquire chemical information on various biological samples, including living tissues in their natural water-rich state. This approach can also be used to study the dynamics of IR-active vibrational modes, that is, measure the decoherence time.

中文翻译：

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飞秒时间分辨红外共振三阶和频光谱

我们展示了基于分子红外（IR）主动共振的相干振动光谱。我们应用两个飞秒脉冲（一个在近红外，另一个在中红外）以生成飞秒时间分辨的红外谐振三阶和频信号。调节中红外脉冲使其与分子振动共振。该实验配置将红外光转换为可见信号，并对分子的振动模式表现出很高的敏感性。该技术可用于获取各种生物样品的化学信息，包括处于天然富水状态的生物组织。这种方法还可以用于研究红外主动振动模式的动力学，即测量退相干时间。