Incorporating real time velocity map image reconstruction into closed-loop coherent control.

Area of Science:

• Physical Chemistry
• Ultrafast Laser Science
• Molecular Dynamics

Background:

• Adaptive femtosecond control requires precise feedback on molecular dynamics.
• Traditional methods for reconstructing 3D momentum from 2D images are slow and labor-intensive.
• Real-time feedback is crucial for optimizing ultrafast laser control schemes.

Purpose of the Study:

• To develop rapid techniques for utilizing 3D momentum information as feedback in adaptive femtosecond control.
• To enable real-time closed-loop control of molecular dynamics using photofragment momentum.
• To demonstrate the application of this method to strong-field dissociation of small molecules.

Main Methods:

• Utilized velocity map imaging to capture 3D momentum maps of dissociating ions.
• Implemented an 'onion-peeling' (back projection) algorithm for rapid inversion of 2D images to 3D momentum.
• Integrated the 3D momentum reconstruction into a closed-loop adaptive control scheme with a genetic algorithm.

Main Results:

• Achieved image inversion in under 1 second for high-resolution (1040 × 1054 pixels) velocity map images.
• Successfully demonstrated closed-loop adaptive control of molecular dissociation using real-time 3D momentum feedback.
• Presented examples of optimizing strong-field dissociation of CO and O2 molecules.

Conclusions:

• Rapid 3D momentum reconstruction enables effective real-time feedback for ultrafast laser control.
• The developed technique significantly advances the capability to steer molecular dynamics with high precision.
• This approach opens new avenues for controlling chemical reactions at the femtosecond timescale.