Ichino Takatoshi, Gianola Adam J, Lineberger W Carl, Stanton John F
JILA, University of Colorado and National Institute of Standards and Technology, Boulder, CO 80309-0440, USA.
J Chem Phys. 2006 Aug 28;125(8):084312. doi: 10.1063/1.2338043.
The 351.1 nm photoelectron spectrum of the 1-pyrazolide-d(3) anion has been measured. The photoelectron angular distributions indicate the presence of nearly degenerate electronic states of the 1-pyrazolyl-d(3) radical. Equation-of-motion ionization potential coupled-cluster singles and doubles (EOMIP-CCSD) calculations have been performed to study the low-lying electronic states. The calculations strongly suggest that three electronic states, energetically close to each other, are accessed in the photodetachment process. Strong interactions of the pseudo-Jahn-Teller type in each pair of the three states are evident in the calculations for the radical at the anion geometry. Model diabatic potentials of the three states have been constructed around the anion geometry in terms of the anion reduced normal coordinates up to the second order. An analytic method to parametrize the quadratic vibronic coupling (QVC) model potentials has been introduced. Parameters of the QVC model potentials have been determined from the EOMIP-CCSD and CCSD(T) calculations. Simulations of the 1-pyrazolide-d(3) spectrum have been performed with the model Hamiltonian, treating all vibronic interactions amongst the three states simultaneously. The simulation reproduces the fine structure of the observed spectrum very well, revealing complicated nonadiabatic effects in the low-lying states of the radical. The ground state of the 1-pyrazolyl-d(3) radical is (2)A(2) and the electron affinity is 2.935+/-0.006 eV. The first excited state is (2)B(1) with a term energy of 32+/-1 meV. While the high-symmetry (C(2v)) stationary points of the X (2)A(2) and A (2)B(1) states are minima, that of the state is a saddle point as a result of the pseudo-Jahn-Teller interactions with the other two states. The topology of the adiabatic potential energy surfaces is discussed.
已测量了1-吡唑啉-d(3)阴离子的351.1 nm光电子能谱。光电子角分布表明存在1-吡唑基-d(3)自由基的近简并电子态。已进行运动方程电离势耦合簇单双激发（EOMIP-CCSD）计算以研究低电子态。计算结果强烈表明，在光剥离过程中可达到三个能量彼此接近的电子态。在阴离子几何构型下对自由基的计算中，这三个态中每一对之间明显存在强的类 Jahn-Teller 型相互作用。已根据阴离子的约化正则坐标构建了围绕阴离子几何构型的这三个态的模型非绝热势，直至二阶。引入了一种对二次振动耦合（QVC）模型势进行参数化的解析方法。QVC模型势的参数已通过EOMIP-CCSD和CCSD(T)计算确定。已使用模型哈密顿量对1-吡唑啉-d(3)光谱进行了模拟，同时处理了这三个态之间的所有振动电子相互作用。模拟结果很好地再现了观测光谱的精细结构，揭示了自由基低电子态中复杂的非绝热效应。1-吡唑基-d(3)自由基的基态为(2)A(2)，电子亲和能为2.935±0.006 eV。第一激发态为(2)B(1)，项能量为32±1 meV。虽然X (2)A(2)和A (2)B(1)态的高对称（C(2v)）驻点是极小值，但由于与其他两个态的类 Jahn-Teller 相互作用，该态的驻点是鞍点。讨论了绝热势能面的拓扑结构。
