Non-Adiabatic Effects on Excited States of Vinylidene Observed with Slow Photoelectron Velocity-Map Imaging
Non-Adiabatic Effects on Excited States of Vinylidene Observed with Slow Photoelectron Velocity-Map Imaging
复制标题
用慢光电子速度图成像观察亚乙烯基激发态的非绝热效应
DOI：
10.1021/jacs.6b10233
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发表时间：
2016-12-21
影响因子：
15
通讯作者：
Neumark, Daniel M.
中科院分区：
文献类型：
--
作者：
DeVine, Jessalyn A.;Weichman, Marissa L.;Neumark, Daniel M.
本文报道了低温冷却的（X）分子在代号B-2（2）H_2CC ~-和D_2CC ~-上亚乙烯基三重激发态区域的高分辨慢光电子速度图成像谱。在基于从头计算的近平衡势能面上观察到三个电子带，并在电子结构计算和量子动力学的帮助下，将其归属为中性偏乙烯基的（a）在波浪线B-3（2）（T-1）上的分离，（B）在波浪线（3）A（2）（T-2）上的分离，和（A）在波浪线（1）A（2）（S-1）上的分离。本工作首次在实验上观察到了H_2CC的（A）过波浪线单重激发态。虽然对于（a）波浪线上和（A）波浪线上电子带观察到规则的振动结构，但在（B）波浪线上电子带振动原点附近分辨出许多不规则特征。高水平的从头计算表明，这种反常结构产生于（a）上波浪线和（B）上波浪线三重态之间的圆锥相交附近的（B）上波浪线态的最低点，这强烈扰动的振动能级在两个电子状态通过非绝热耦合。利用Ervin及其同事先前测量的H2 CC的绝热电子亲和势为0.490（6）eV [J. Chem. Phys. 1989，91，5974]，发现H2 CC的激发中性态的项能量为T-0（（a）/波浪线B-3（2））= 2.064（6），T-0（（B）相对于波浪线（3）A（2））= 2.738（6），且T-0（（A）相对于波浪线（1）A（2））= 2.991（6）eV。
High-resolution slow photoelectron velocity-map imaging spectra of cryogenically cooled (X) over tilde B-2(2) H2CC- and D2CC- in the region of the vinylidene triplet excited states are reported. Three electronic bands are observed and, with the assistance of electronic structure calculations and quantum dynamics on ab initio-based near-equilibrium potential energy surfaces, are assigned as detachment to the (a) over tilde B-3(2) (T-1), (b) over tilde (3)A(2) (T-2), and (A) over tilde (1)A(2) (S-1) excited states of neutral vinylidene. This work provides the first experimental observation of the (A) over tilde singlet excited state of H2CC. While regular vibrational structure is observed for the (a) over tilde and (A) over tilde electronic bands, a number of irregular features are resolved in the vicinity of the (b) over tilde band vibrational origin. High-level ab initio calculations suggest that this anomalous structure arises from a conical intersection between the (a) over tilde and (b) over tilde triplet states near the (b) over tilde state minimum, which strongly perturbs the vibrational levels in the two electronic states through nonadiabatic coupling. Using the adiabatic electron affinity of H2CC previously measured to be 0.490(6) eV by Ervin and co-workers [J. Chem. Phys. 1989, 91, 5974], term energies for the excited neutral states of H2CC are found to be T-0((a) over tilde B-3(2)) = 2.064(6), T-0((b) over tilde (3)A(2)) = 2.738(6), and T-0((A) over tilde (1)A(2)) = 2.991(6) eV.