2-甲基呋喃分子激发态超快非绝热动力学（英文）

Ultrafast Nonadiabatic Dynamics of Electronically Excited 2-Methyl Furan

利用飞秒时间分辨的光电子影像技术研究了2-甲基呋喃分子激发态超快非绝热动力学。2-甲基呋喃分子吸收两个400 nm的光子后同时被激发到n=3的里德堡态S1[~1A′′(π3s)]、~1A′(π3p_x)、~1A″(π3p_y)、~1A″(π3p_z)和价电子态~1A′(ππ*),之后被两个800 nm的光子电离。通过母体离子产率随泵浦-探测延迟时间的变化曲线测得这些里德堡态与价电子态的平均寿命为50 fs。通过解析光电子能谱中n=3的里德堡态与价电子态所对应的组分峰的相对演化特征,观测到了这些激发态之间的内转换过程,并且揭示了价电子态~1A′(ππ*)在内转换过程中扮演的重要"纽带"作用。里德堡态与价电子态之间的混合,形成势能面间的锥形交叉,导致了如此超快的内转换过程。

Excited-state dynamics of 2-methyl furan has been studied by femtosecond time-resolved photoelectron imaging. The molecule 2-methyl furan was simultaneously excited to the n = 3 Rydberg series of S1[1A＂（π3s）], 1A＇（π3p,）, 1A＂（π3py） and 1A＂（π3pz） and the valence state of 1A＇（ππ＊） by two 400 nm photons and subsequently probed by two 800 nm photons. The average lifetime of the Rydberg series and the valence state was measured to be on the time scale of 50 fs by the time-dependent ion yield of the parent ion. Ultrafast internal conversions among these excited states were observed and extracted from the time-dependences of the photoelectron kinetic energy components of these excited states in the photoelectron kinetic energy spectra. Furthermore, it is identified that the ＇A＇（ππ＊） state might play an important role in internal conversions among these excited states. The Rydberg-valence mixings, which result in numerous conical intersections, act as the driving force to accomplish such ultrafast internal conversions.