Yuan Wenpeng, Yang Dongyuan, Feng Baihui, Min Yanjun, Chen Zhichao, Yu Shengrui, Wu Guorong, Yang Xueming
Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou, Zhejiang 311231, China.
Phys Chem Chem Phys. 2021 Aug 28;23(32):17625-17633. doi: 10.1039/d1cp01090e. Epub 2021 Aug 9.
The excited-state decay dynamics of 2-ethylpyrrole following UV excitation in the wavelength range of 254.8-218.0 nm is investigated in detail using the femtosecond time-resolved photoelectron imaging method. The time-resolved photoelectron spectra and photoelectron angular distributions at all pump wavelengths are carefully analysed and the following picture is derived: at the longest pump wavelengths (254.8, 248.3 and 246.1 nm), 2-ethylpyrrole is excited to the S(πσ*) state having a lifetime of about 50 fs. At 248.3, 246.1 and 237.4 nm, another excited state of Rydberg character is excited. The lifetime of this state is ∼570 fs at 237.4 nm and becomes slightly longer at other two pump wavelengths. At the shortest pump wavelengths (230.8 and 218.0 nm), 2-ethylpyrrole is excited to a state which is tentatively assigned to the 1ππ* state, having a lifetime of 75 ± 15 and 48 ± 10 fs for the longer and shorter pump wavelengths, respectively. Internal conversion to the S(πσ*) state might be one of the decay mechanisms of the 1ππ* state.
采用飞秒时间分辨光电子成像方法，详细研究了2-乙基吡咯在254.8 - 218.0 nm波长范围内紫外激发后的激发态衰变动力学。仔细分析了所有泵浦波长下的时间分辨光电子能谱和光电子角分布，得出以下情况：在最长泵浦波长（254.8、248.3和246.1 nm）下，2-乙基吡咯被激发到寿命约为50 fs的S(πσ*)态。在248.3、246.1和237.4 nm处，另一个具有里德堡特征的激发态被激发。该态在237.4 nm处的寿命约为570 fs，在其他两个泵浦波长下略长。在最短泵浦波长（230.8和218.0 nm）下，2-乙基吡咯被激发到一个暂定为1ππ态的状态，对于较长和较短泵浦波长，其寿命分别为75±15 fs和48±10 fs。内转换为S(πσ)态可能是1ππ*态的衰变机制之一。
