Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37931, USA.
J Chem Phys. 2012 Apr 7;136(13):134303. doi: 10.1063/1.3697472.
The quadricyclane-norbornadiene system is an important model for the isomerization dynamics between highly strained molecules. In a breakthrough observation for a polyatomic molecular system of that complexity, we follow the photoionization from Rydberg states in the time-domain to derive a measure for the time-dependent structural dynamics and the time-evolving structural dispersion even while the molecule is crossing electronic surfaces. The photoexcitation to the 3s and 3p Rydberg states deposits significant amounts of energy into vibrational motions. We observe the formation and evolution of the vibrational wavepacket on the Rydberg surface and the internal conversion from the 3p Rydberg states to the 3s state. In that state, quadricyclane isomerizes to norbornadiene with a time constant of τ(2) = 136(45) fs. The lifetime of the 3p Rydberg state in quadricyclane is τ(1) = 320(31) and the lifetime of the 3s Rydberg state in norbornadiene is τ(3) = 394(32).
四环烷-降蒈烯体系是高度应变分子之间异构化动力学的重要模型。在对这种复杂的多原子分子体系的突破性观察中，我们在时域中跟随里德堡态的光致电离，以得出时间相关结构动力学的度量，以及即使分子在穿过电子表面时也在不断发展的结构色散。3s 和 3p 里德堡态的光激发将大量能量沉积到振动运动中。我们观察到在里德堡表面上形成和演化的振动波包，以及从 3p 里德堡态到 3s 态的内部转换。在该状态下，四环烷异构化为降蒈烯，时间常数为 τ(2)=136(45)fs。四环烷中 3p 里德堡态的寿命为 τ(1)=320(31)，而降蒈烯中 3s 里德堡态的寿命为 τ(3)=394(32)。
