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飞秒瞬态吸收光谱直接观测光化学反应——以激发态分子内质子转移为例

扶鹏雁1, 潘梅2,3   

  1. 1 湖南师范大学化学化工学院, 湖南 长沙 410081;
    2 中山大学化学学院, 广东 广州 510006;
    3 新疆大学化学学院, 新疆 乌鲁木齐 830017
  • 收稿日期:2026-06-02 录用日期:2026-08-05
  • 通讯作者: 潘梅 E-mail:panm@mail.sysu.edu.cn Mei Pan
  • 基金资助:
    湖南省教育厅优秀青年项目(25B0100)，广州市科技计划项目(2025B01J4001)

Femtosecond transient absorption spectroscopy for direct observation of photochemical reactions: a case study of excited-state intramolecular proton transfer

Pengyan Fu1, Mei Pan2,3   

  1. 1 College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, Hunan Province, China;
    2 School of Chemistry, Sun Yat-Sen University, Guangzhou 510006, Guangdong Province, China;
    3 School of Chemistry, Xinjiang University, Urumqi 830017, Xinjiang, China
  • Received:2026-06-02 Accepted:2026-08-05
  • Contact: Mei Pan E-mail:panm@mail.sysu.edu.cn

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摘要： 光化学反应中关键的电子结构重排过程常发生于飞秒至皮秒尺度，传统稳态光谱方法难以探测其动态演变，成为实际教学中的一个抽象难点。飞秒瞬态吸收光谱是一种基于泵浦-探测原理的超快光谱技术，能够在飞秒至纳秒时间尺度上直接观测光化学反应中的瞬态中间体及其演化动力学。本文以激发态分子内质子转移这一典型光化学反应为例，系统介绍该技术的发展历程、原理、三类特征信号及其物理意义。以Cbz-HPNI-COOH分子为模型体系，通过中性与酸性条件下的动力学对比，直观展示了分子内氢键状态对质子转移速率的决定作用。文章旨在帮助化学及相关专业师生建立对超快光化学动态过程的直观认识，理解瞬态吸收光谱作为连接分子结构与反应动力学的桥梁作用。

关键词: 飞秒瞬态吸收光谱, 泵浦-探测, 激发态分子内质子转移, 超快动力学, 光化学

Abstract: The critical electronic rearrangement processes underlying photochemical reactions typically unfold on the femtosecond to picosecond timescale, rendering them inaccessible to conventional steady-state spectroscopic techniques and posing a conceptual challenge in pedagogical settings. Femtosecond transient absorption spectroscopy, an ultrafast technique based on the pump-probe principle, enables direct tracking of transient intermediates and their dynamical evolution over timescales ranging from femtoseconds to nanoseconds. Using excited-state intramolecular proton transfer as a representative photochemical reaction, this article systematically reviews the development, working principles, and three types of characteristic signals of this technique, along with their physical interpretations. Employing the Cbz-HPNI-COOH molecule as a model system, comparative kinetic analyses under neutral and acidic conditions vividly illustrate how the intramolecular hydrogen-bonding environment governs the proton transfer rate. This contribution aims to equip students and educators in chemistry and allied disciplines with an intuitive grasp of ultrafast photochemical dynamics and to underscore the role of transient absorption spectroscopy as a pivotal bridge between molecular structure and reaction kinetics.

Key words: Femtosecond transient absorption spectroscopy, Pump-probe, Excited-state intramolecular proton transfer, Ultrafast dynamics, Photochemistry