Tom Weinacht’s Research

Controlling thedetailed behavior of atoms and molecules with light has been a major goal since the invention of the laser. Amplified ultrafast lasers provide us with a unique tool for manipulating the internal dynamics of atomic and molecular systems. With field strengths greater than the binding field for atomic electrons and time durations shorter than vibrational and rotational periods in molecules, such lasers can exert strong forces on molecular and atomic timescales. Using recent advances in ultrafast laser technology, the shape of electric field pulses can also be tailored, allowing us to control the forces that we apply to atoms and molecules.
Our research centers upon preparing, controlling, and measuring dynamical states in quantum systems. Our strong pulses allow us to create and control wave packet states, whose time evolution we can watch with a variety of time-resolved spectroscopic techniques

Thus ultrafast laser pulses also provide us with a flexible, high-resolution measurement tool. The short time durations and high intensities of the pulses allow for strobing dynamics and performing nonlinear time resolved spectroscopies, which can provide new information not available from other measurements.

One of our main goals is to use shaped light pulses as selective catalysts for chemical reactions. Recently there has been much excitement about experiments that use shaped pulses to control simple reactions, such as breaking one bond in a polyatomic molecule while leaving others intact. We would like to increase our understanding of such experiments, and extend control to a broader class of reactions.

The design of appropriate fields for controlling atoms and molecules on their natural timescales is a difficult task. By using a learning algorithm such as the Genetic Algorithm to direct the choice of optical pulse shape, we can find optimal light fields to do this. Coherently prepared atoms and molecules can, in turn, be used as ultrafast optical modulators and sources. Strongly driven atoms can emit x-rays, and vibrating or rotating molecules have been used to generate the shortest visible light pulses in the world.