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A quantum molecular movie: polyad predissociation dynamics in the VUV excited 3pσ2Σu state of NO2
Faraday Discussions ( IF 3.3 ) Pub Date : 2020-12-22 , DOI: 10.1039/d0fd00128g
Varun Makhija 1, 2, 3, 4, 5 , Andrey E. Boguslavskiy 5, 6, 7, 8, 9 , Ruaridh Forbes 5, 6, 7, 8, 10 , Kevin Veyrinas 5, 6, 7, 8 , Iain Wilkinson 11, 12, 13, 14 , Rune Lausten 7, 8, 9 , Michael S. Schuurman 6, 7, 8, 9, 15 , Edward R. Grant 15, 16, 17, 18 , Albert Stolow 5, 6, 7, 8, 9
Affiliation  

The optical formation of coherent superposition states, a wavepacket, can allow the study of zeroth-order states, the evolution of which exhibit structural and electronic changes as a function of time: this leads to the notion of a molecular movie. Intramolecular vibrational energy redistribution, due to anharmonic coupling between modes, is the molecular movie considered here. There is no guarantee, however, that the formed superposition will behave semi-classically (e.g. Gaussian wavepacket dynamics) or even as an intuitively useful zeroth-order state. Here we present time-resolved photoelectron spectroscopy (TRPES) studies of an electronically excited triatomic molecule wherein the vibrational dynamics must be treated quantum mechanically and the simple picture of population flow between coupled normal modes fails. Specifically, we report on vibronic wavepacket dynamics in the zeroth-order 3pσ2Σu Rydberg state of NO2. This wavepacket exemplifies two general features of excited state dynamics in polyatomic molecules: anharmonic multimodal vibrational coupling (forming polyads); nonadiabatic coupling between nuclear and electronic coordinates, leading to predissociation. The latter suggests that the polyad vibrational states in the zeroth-order 3p Rydberg manifold are quasi-bound and best understood to be scattering resonances. We observed a rapid dephasing of an initially prepared ‘bright’ valence state into the relatively long-lived 3p Rydberg state whose multimodal vibrational dynamics and decay we monitor as a function of time. Our quantum simulations, based on an effective spectroscopic Hamiltonian, describe the essential features of the multimodal Fermi resonance-driven vibrational dynamics in the 3p state. We also present evidence of polyad-specificity in the state-dependent predissociation rates, leading to free atomic and molecular fragments. We emphasize that a quantum molecular movie is required to visualize wavepacket dynamics in the 3pσ2Σu Rydberg state of NO2.

中文翻译:

量子分子电影:VUV激发的NO2的3pσ2Σu态下的多聚体预解离动力学

相干叠加态的光学形成(一个波包)可以研究零阶状态,其演化表现出结构和电子随时间的变化:这导致了分子电影的概念。由于模式之间的非谐耦合,分子内振动能的重新分配是此处考虑的分子电影。但是,不能保证所形成的叠加将表现为半经典的行为(例如,高斯波包动力学)或什至是直观上有用的零阶状态。在这里,我们目前对电子激发的三原子分子进行时间分辨光电子能谱研究(TRPES),其中必须对振动动力学进行量子力学处理,而耦合的正常模式之间的人口流动简单图则失败了。具体来说,我们在零阶上的电子振动波包动力学报告3pσ 2 Σ ü NO的里德堡态2。该波包例证了多原子分子中激发态动力学的两个一般特征:非谐多峰振动耦合(形成多单元);核坐标和电子坐标之间的非绝热耦合,导致预解离。后者表明零阶3p Rydberg流形中的多元振动状态是准绑定的,最好理解为散射共振。我们观察到,最初准备的“亮”价态迅速移相到寿命相对较长的3p Rydberg态,该态的多模态振动动力学和衰减随时间而变化。我们基于有效光谱哈密顿量的量子模拟描述了3p态下多峰费米共振驱动振动动力学的基本特征。我们还提出了在状态依赖的预解离速率中,导致游离原子和分子碎片的多聚体特异性的证据。我们强调需要一个量子分子电影来可视化3pσ中的波包动力学2 Σ ü NO的里德伯状态2
更新日期:2021-02-25
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