Short-wavelength probes in time-resolved photoelectron spectroscopy: an extended view of the excited state dynamics in acetylacetone
Short-wavelength probes in time-resolved photoelectron spectroscopy: an extended view of the excited state dynamics in acetylacetone
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DOI：
10.1039/d0cp00068j
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发表时间：
2020-02-28
影响因子：
3.3
通讯作者：
Townsend, Dave
中科院分区：
文献类型：
--
作者：
Kotsina, Nikoleta;Candelaresi, Marco;Townsend, Dave
真空紫外线(VUV)光谱区的飞秒脉冲光允许对气相分子中的非绝热动力学进行扩展观察。当用作时间分辨光电子能谱的探针时，这种脉冲可以深入电离连续体，并允许跨多个势能面监测激发态布居的演化。与更长波长的探头相比，这通常提供了连接光反应物和光产品的反应坐标(S)上更完整的图像。本文报道了用160 nm真空紫外光研究乙酰丙酮在267 nm激发后的激发态动力学。在从几飞秒到数百皮秒的时间尺度上观察到了多种非绝热过程(内部转换和系统间交叉)。我们的定量结果与早先的研究非常一致，这些研究分别采样了总反应坐标的较小部分。此外，我们还观察到了以前在其他地方没有报道的额外的动态特征。总体而言，我们的发现很好地说明了在基于光电离的光化学动力学研究中使用短波长VUV探测器以获得最全面的图像的必要性。
Femtosecond pulses of light in the vacuum ultraviolet (VUV) spectral region permit extended observation of non-adiabatic dynamics in gas-phase molecules. When used as a probe in time-resolved photoelectron spectroscopy, such pulses project deeply into the ionization continuum and allow the evolution of excited state population to be monitored across multiple potential energy surfaces. When compared with longer-wavelength probes, this often provides a more complete view along the reaction coordinate(s) connecting photoreactants to photoproducts. Here we report the use of 160 nm VUV light to interrogate the excited state dynamics operating in acetylacetone following 267 nm excitation. Multiple non-adiabatic processes (internal conversion and intersystem crossing) were observed on timescales ranging from a few femtoseconds to hundreds of picoseconds. Our quantitative results are in excellent agreement with earlier studies that individually sampled smaller sub-sections of the total reaction coordinate. Furthermore, we also observe additional dynamical signatures not previously reported elsewhere. Overall, our findings provide a good illustration of the need to use short-wavelength VUV probes to obtain the most comprehensive picture possible in photoionization-based studies of photochemical dynamics.