Barge Vishal J, Hu Zhan, Gordon Robert J
Department of Chemistry (m/c 111), University of Illinois at Chicago, Chicago, Illinois 60680-7061, USA.
J Chem Phys. 2008 Dec 28;129(24):244301. doi: 10.1063/1.3040269.
The electric field of a light wave accumulates a pi phase shift as it passes through a focus. We show here how this effect, known as the Gouy phase, may be used to control the branching ratio of a unimolecular reaction when the products are formed with different numbers of photons. We demonstrate this control method for the ionization and dissociation of vinyl chloride, using absorption of 177 and 532 nm photons to induce a pair of interfering paths. Excellent agreement between the observed and calculated phase shift as a function of the axial coordinate of the laser focus indicates that fragmentation occurs via a ladder switching mechanism. The axial dependence of the modulation depth is evidence of loss of coherence at higher internal temperatures of the molecule.
当光波通过焦点时，其电场会累积π相移。我们在此展示了这种被称为古依相的效应如何用于控制单分子反应的分支比，前提是产物由不同数量的光子形成。我们以氯乙烯的电离和解离为例演示了这种控制方法，利用177纳米和532纳米光子的吸收来诱导一对干涉路径。观察到的相移与作为激光焦点轴向坐标函数计算出的相移之间的出色一致性表明，碎片化是通过阶梯切换机制发生的。调制深度的轴向依赖性证明了在分子内部温度较高时相干性的丧失。
