Dillon Joseph J, Yarkony David R
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Chem Phys. 2009 Apr 21;130(15):154312. doi: 10.1063/1.3109992.
The negative ion photoelectron spectrum of the isopropoxide anion is determined using the multimode vibronic coupling approach. The simulated spectrum is based on a two state quasidiabatic Hamiltonian for the isopropoxy radical, H(d), which includes all terms through second-order order in all internal coordinates and accurately represents the vicinity of the ab initio determined equilibrium geometry of the ground electronic state as well as the minimum energy crossing point (MECP) on the symmetry-allowed (2)A(")-(2)A(') accidental seam of conical intersection. H(d) is centered at the (2)A(")-(2)A(') MECP and is determined from ab initio gradients and derivative couplings using a normal equations based algorithm. Spin-orbit effects are included using a generalization of a procedure due to Child and Longuet-Higgins. The nonadiabatic interactions coupling the (2)A(") and (2)A(') states are very similar to those found in an Exe Jahn-Teller system although the requisite symmetry is absent. The simulated photoelectron spectrum for isopropoxide-h(7) is compared to a measured photoelectron spectrum and the results of a dispersed fluorescence experiment on the isopropoxy radical. The nominal A (2)A-X (2)A splitting of 68 cm(-1) from the dispersed fluorescence experiment is confirmed. This splitting is shown to be a consequence of the accidental Jahn-Teller symmetry and the spin-orbit interaction so that the standard designation of this spectral feature as the A-X splitting is not appropriate. This spectral feature is better thought of as the spin-orbit splitting of a nearly degenerate ground state. It is further shown that the intensities and line positions are such that the origin band of the nominal A (2)A state and that of the X (2)A state could not be distinguished with the resolution available in the photoelectron experiment. The photoelectron spectrum of the completely deuterated analog, isopropoxide-d(7), is also reported and discussed.
使用多模振动耦合方法测定了异丙氧基阴离子的负离子光电子能谱。模拟光谱基于异丙氧基自由基H(d)的双态准绝热哈密顿量，其中包括所有内坐标中二阶以内的所有项，并准确表示了从头算确定的基态电子态平衡几何结构附近以及对称允许的(2)A″-(2)A′偶然锥形交叉缝上的最小能量交叉点(MECP)。H(d)以(2)A″-(2)A′ MECP为中心，通过基于正规方程的算法由从头算梯度和导数耦合确定。自旋轨道效应通过Child和Longuet-Higgins方法的推广来包含。耦合(2)A″和(2)A′态的非绝热相互作用与Exe Jahn-Teller系统中的非常相似，尽管缺乏必要的对称性。将异丙氧基-h(7)的模拟光电子能谱与实测光电子能谱以及异丙氧基自由基的色散荧光实验结果进行了比较。色散荧光实验中68 cm(-1)的标称A (2)A-X (2)A分裂得到了证实。这种分裂被证明是偶然的Jahn-Teller对称性和自旋轨道相互作用的结果，因此将该光谱特征标准指定为A-X分裂是不合适的。这个光谱特征更好地被认为是近简并基态的自旋轨道分裂。进一步表明，强度和谱线位置使得在光电子实验可用的分辨率下无法区分标称A (2)A态和X (2)A态的起源带。还报道并讨论了完全氘代类似物异丙氧基-d(7)的光电子能谱。
