Advanced Ultrafast Laser Research Center, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan.
Phys Chem Chem Phys. 2012 May 14;14(18):6200-10. doi: 10.1039/c2cp23649d. Epub 2012 Feb 21.
Time-resolved transient absorption spectroscopy with sub-9 fs ultrashort laser pulses in the deep-ultraviolet (DUV) region is reported for the first time. Single 8.7 fs DUV pulses with a spectral range of 255-290 nm are generated by a chirped-pulse four-wave mixing technique for use as pump and probe pulses. Electronic excited state and vibrational dynamics are simultaneously observed for an aqueous solution of thymine over the full spectral range using a 128-channel lock-in detector. Vibrational modes of the electronic ground state and excited states can be observed as well as the decay dynamics of the electronic excited state. Information on the initial phase of the vibrational modes is extracted from the measured difference absorbance trace, which contains oscillatory structures arising from the vibrational modes of the molecule. Along with other techniques such as time-resolved infrared spectroscopy, spectroscopy with sub-9 fs DUV pulses is expected to contribute to a detailed understanding of the photochemical dynamics of biologically significant molecules that absorb in the DUV region such as DNA and amino acids.
首次报道了在深紫外（DUV）区域使用亚 9 fs 超短激光脉冲的时间分辨瞬态吸收光谱。通过啁啾脉冲四波混频技术产生了单个 8.7 fs 的 DUV 脉冲，光谱范围为 255-290nm，用作泵浦和探测脉冲。使用 128 通道锁相探测器，在整个光谱范围内同时观察到胸腺嘧啶水溶液的电子激发态和振动动力学。可以观察到电子基态和激发态的振动模式以及电子激发态的衰减动力学。从测量的差分吸收迹线中提取出振动模式的初始相位信息，该迹线包含源自分子振动模式的振荡结构。与其他技术（如时间分辨红外光谱）一样，亚 9 fs DUV 脉冲光谱有望有助于深入了解在 DUV 区域吸收的具有生物学意义的分子（如 DNA 和氨基酸）的光化学反应动力学。
