Quantum coherent control of ultrafast bond making and the subsequent molecular dynamics is crucial for the realization of a new photochemistry, where a shaped laser field is actively driving the chemical system in a coherent way from the thermal initial state of the reactants to the final state of the desired products. We demonstrate here coherent control over the relative yields of Mg₂ molecules that are generated via photoassociation and subsequently photodriven into different groups of final states. The strong-field process involves non-resonant multiphoton femtosecond photoassociation of a pair of thermally hot magnesium atoms into a bound Mg₂ molecule and subsequent molecular dynamics on electronically excited states. The branching-ratio control is achieved with linearly chirped laser pulses, utilizing the different chirp dependence that various groups of final molecular states display for their post-pulse population. Our joint experimental and theoretical study establishes the feasibility of high degree coherent control over quantum molecular dynamics that is initiated by femtosecond photoassociation of thermal atoms.

超快键形成的量子相干控制和随后的分子动力学对于实现新的光化学至关重要，其中成形的激光场以相干方式主动驱动化学系统从反应物的热初始状态到最终状态所需的产品。我们在这里展示了对通过光缔合产生的 Mg ₂分子的相对产率的连贯控制，随后光驱进入不同的最终状态组。强场过程涉及一对热镁原子的非共振多光子飞秒光缔合成为束缚的 Mg ₂分子和随后的电子激发态分子动力学。分支比控制是通过线性啁啾激光脉冲实现的，利用不同的啁啾依赖性，各种最终分子状态组为其后脉冲群显示。我们的联合实验和理论研究确立了对由热原子的飞秒光缔合引发的量子分子动力学进行高度相干控制的可行性。