Molecular Physics seminar

Polyatomic Molecules in Laser Fields: Non-adiabatic Dynamics, Quantum Control, Strong Field Physics

by Prof. Albert Stolow (National Research Council, Canada)

FB52 ()


Time-Resolved Photoelectron Spectroscopy (TRPES) is a powerful femtosecond probe of non-adiabatic dynamics in polyatomic molecules [1]. In Time-Resolved Coincidence Imaging Spectroscopy (TRCIS), we make use of 3D particle timing-imaging detectors for full 3D momentum vector determination of coincident photoions and photoelectrons as a function of time. This 6D information allows for study of the time evolution of both scalar and vector correlations during molecular processes. We discuss the use of these, illustrated by the example of the photodissociation of the NO dimer. One vector correlation is particularly interesting as it permits Angle-Energy resolved TRPES studies from the molecular frame rather than the lab frame point of view [2]. We then consider the non-resonant, nonperturbative Dynamic Stark Effect as a new and powerful tool for Quantum Control. Dynamic Stark Control (DSC) applies to both molecular rotation and vibration. We show how DSC, which uses the strong electric field intensity envelope of an infrared laser pulse, can be used to align molecules in the lab frame so the time-resolved measurements can be performed in the molecualar frame [3]. We also show how DSC can be used to control electronic branching ratios in molecular dissociation, without any absorption of light [4]. As fields get stronger still, a new physics emerges where both the single active electron picture and the adiabatic electron response in the field can fail dramatically. A new Nonadiabatic Multi-Electron (NME) dynamics emerges and has important consequences for all strong field probing of polyatomic molecules. [1] Nature 401, 52, (1999); Advances in Chemical Physics 139, 497 (2008) [2] Science 311, 219 (2006) [3] Science 323, 1464 (2009) [4] Science 314, 278 (2006)