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首页> 外文期刊>The Journal of Chemical Physics >Broadband transient absorption spectroscopy with 1-and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution
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Broadband transient absorption spectroscopy with 1-and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution

机译：具有1和2光子激发的宽带瞬态吸收光谱：溶液中三苯胺染料的弛豫路径和截面

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摘要

1-photon (382 nm) and 2-photon (752 nm) excitations to the S-1 state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S-1 -> S-n due to resonant absorption of a third pump photon. Subsequent S-n -> S-1 internal conversion (with tau(1) = 1 ps) prepares a very hot S-1 state which cools down with tau(2) = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections sigma((2)) = 32 . 10(-50) cm(4) s at 752 nm are evaluated from the bleach signal. (C) 2015 AIP Publishing LLC.
机译：施加至S-1状态的1光子（382 nm）和2光子（752 nm）激发来记录和比较溶液中推挽式三苯胺（TrP）染料的瞬态吸收光谱。在1光子激发后，在非极性己烷中以0.1 ps的时间尺度检测到超快的振动和结构分子弛豫，而在极性乙腈中，光谱演化以偶极溶剂化为主。在2光子激发后，己烷中的瞬态光谱显示出受激发射（SE）和激发态吸收（ESA）谱带的意外增长。该行为由第三泵浦光子的共振吸收引起的强种群转移S-1-> S-n解释。随后的S-n-> S-1内部转换（tau（1）= 1 ps）准备了一个非常热的S-1状态，它在tau（2）= 13 ps时冷却下来。泵浦脉冲能量依赖性证明了漂白信号的2光子起源。同时，SE和ESA受高阶泵浦吸收的强烈影响，在非线性荧光应用中应考虑在内。 2光子激发截面sigma（（2））= 32。从漂白信号评估在752 nm处10（-50）cm（4）s。 （C）2015 AIP Publishing LLC。

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