Liebel Matz, Kukura Philipp
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
J Phys Chem Lett. 2013 Apr 18;4(8):1358-64. doi: 10.1021/jz4004203. Epub 2013 Apr 9.
We demonstrate that transient absorption spectroscopy performed with an ultrashort pump pulse and a chirped, broad-band probe pulse is capable of recording full vibrational spectra of excited electronic states in the time domain. The resulting spectra do not suffer from the nontrivial baselines and line shapes often encountered in frequency domain techniques and enable optimal and automated subtraction of background signatures. Probing the molecular dynamics continuously over a broad energy bandwidth makes it possible to confidently assign the vibrational coherences to specific electronic states and suggests the existence of mode-specific absorption spectra reminiscent of resonance Raman intensity analysis. The first observation of the nominally forbidden one-photon ground to first excited electronic state transition in β-carotene demonstrates the high sensitivity of our approach. Our results provide a first glimpse of the immense potential of broad-band impulsive vibrational spectroscopy (BB-IVS) to study ultrafast chemical reaction dynamics.
我们证明，用超短泵浦脉冲和啁啾宽带探测脉冲进行的瞬态吸收光谱能够在时域中记录激发电子态的完整振动光谱。所得光谱不会受到频域技术中经常遇到的复杂基线和线形的影响，并能够对背景信号进行最佳和自动的扣除。在宽能量带宽上连续探测分子动力学，使得能够可靠地将振动相干性归因于特定的电子态，并表明存在类似于共振拉曼强度分析的模式特异性吸收光谱。在β-胡萝卜素中首次观察到名义上禁止的从基态到第一激发电子态的单光子跃迁，证明了我们方法的高灵敏度。我们的结果首次展示了宽带脉冲振动光谱（BB-IVS）在研究超快化学反应动力学方面的巨大潜力。
