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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Cycloreversion Dynamics of a Photochromic Molecular Switch via One-Photon and Sequential Two-Photon Excitation
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Cycloreversion Dynamics of a Photochromic Molecular Switch via One-Photon and Sequential Two-Photon Excitation

机译：通过一光子和顺序两光子激发的光致变色分子开关的回旋动力学

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摘要

Ultrafast pump?probe (PP) and pump?repump?probe (PReP) measurements examine the ring-opening reaction of a photochromic molecular switch following excitation to the first and higher excited states. Sequential two-photon excitation is a sensitive probe of the excited-state dynamics, because the secondary excitation maps the progress along the S1 reaction coordinate onto the higher excited states of the molecule. In this contribution, secondary excitation at 800 nm accesses more reactive regions of the excited-state potential energy surfaces than are accessible with direct vertical excitation in the visible or UV. The quantum yield for cycloreversion increases by a factor of 3.5 ± 0.9 compared with one-photon excitation when the delay between the 500 nm pump and 800 nm repump laser pulses increases beyond ~100 fs, in contrast with a slower ~3 ps increase that was previously observed for one-color sequential excitation at 500 nm. The evolution of an excited-state absorption band reveals the dynamics of the higher-lying excited state for both one-photon excitation in the UV and sequential two-photon excitation. The spectroscopy and dynamics of the higher-lying excited state are similar for both excitation pathways, including a lifetime of ~100 fs. The complementary PP and PReP measurements provide a detailed picture of the ultrafast excited-state dynamics, including new insight on the role of excited states above S1 in controlling the photochemical cycloreversion reaction.
机译：超快泵浦探针（PP）和泵浦泵浦探针（PReP）测量可以检测光致变色分子开关在激发到第一和更高激发态后的开环反应。顺序双光子激发是激发态动力学的灵敏探针，因为二次激发将沿着S1反应坐标的进展映射到分子的更高激发态。在这种贡献中，与在可见光或紫外光中直接垂直激发相比，在800 nm处的二次激发可以访问激发态势能表面的更多反应区域。当500 nm泵浦和800 nm泵浦激光脉冲之间的延迟增加超过〜100 fs时，与单光子激发相比，环还原的量子产率提高了3.5±0.9倍，而增加了约3 ps以前在500 nm处观察到一种颜色的连续激发。激发态吸收带的演化揭示了紫外光中单光子激发和连续两光子激发中较高激发态的动力学。两种激发途径的较高激发态的光谱和动力学都相似，包括约100 fs的寿命。互补的PP和PReP测量提供了超快激发态动力学的详细图片，包括关于S1以上激发态在控制光化学环还原反应中的作用的新见解。

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