Yang Jie, Li Juan, Mo Yuxiang
Department of Physics, Tsinghua University, Bejing 100084, China.
J Chem Phys. 2006 Nov 7;125(17):174313. doi: 10.1063/1.2359725.
The vibrational structures of the electronic ground states ((approximately)X (2)A(2)) of furan, pyrrole, and thiophene cations have been studied by zero kinetic energy (ZEKE) photoelectron spectroscopic method. In addition to the strong excitations of the symmetric a(1) vibrational modes, other three symmetric vibrational modes (a(2), b(1), and b(2)) have been observed unambiguously. These results which cannot be explained by the Franck-Condon principle illustrate that the vibronic coupling and the Coriolis coupling may play important roles in understanding the vibrational structures of the five-membered heterocycle cations. The vibrationally resolved ZEKE spectra are assigned with the assistance of the density function theory calculations, and the fundamental frequencies for many vibrational modes have been determined for the first time. The first adiabatic ionization energies for furan, pyrrole, and thiophene were determined as 8.8863, 8.2099, and 8.8742 eV, respectively, with uncertainties of 0.0002 eV.
采用零动能（ZEKE）光电子能谱法研究了呋喃、吡咯和噻吩阳离子电子基态（（近似）X²A₂）的振动结构。除了对称a₁振动模式的强烈激发外，还明确观察到了其他三种对称振动模式（a₂、b₁和b₂）。这些无法用弗兰克-康登原理解释的结果表明，振动-电子耦合和科里奥利耦合在理解五元杂环阳离子的振动结构中可能起重要作用。借助密度泛函理论计算对振动分辨的ZEKE光谱进行了归属，首次确定了许多振动模式的基频。呋喃、吡咯和噻吩的第一绝热电离能分别确定为8.8863、8.2099和8.8742 eV，不确定度为0.0002 eV。
