多原子分子在强飞秒激光场中的解离

Dissociation of Polyatomic Molecules in the Intense Femtosecond Laser Field

强场化学是一个新的研究领域,分子在强激光场中解离则是该领域中的一个重要课题.本文阐述分子在强飞秒激光场(1013～1014W·cm-2)中的解离规律以及我们所提出的场致解离(FAD)理论.在模型中我们考虑的是分子离子的解离,而且只考虑那些键轴平行于激光场方向的离子.此模型要求先计算出分子离子的缀饰势能面(DressedPES),再计算键长随时间变化的准经典轨线(QCT).以甲烷、丙酮为例进行了实验和理论研究,理论计算的结果能很好地阐明观察到的实验结果.

Chemistry in strong laser fields is a new research field in which dissocia tion of molecules in the intense laser field is a current topic of inte rest.Our results,including the theoretical model of field-assisted di ssociation(FAD)and the experimental investigation s on the dissociation of CH 4 and CH 3 COCH 3 in the intense femtosecond laser field are presented.Some assu mptions are made in the model.When a l aser field applies to a molecule,onl y the change of the one bond length,whi ch lies along with the laser field,is taken into account and the rest of the molecular geometry is fixed.In addi tion,only molecular ions in the ground electronic state are considered.Ab initio potential energy surfaces in the ext ernal fields indicate that chemical bond tends to dissociate.QCT(quasi-classical trajectory)calculations clearly show the proce sses of bond breaking.It was found th at the calculations based on the theoretical model are in excellent agreement with the experiment data.