VOLUME 1, ISSUE 5, 2017

Controlling Coherence in The Product Channel from a Direct, Uni-Molercular Dissociation Reaction

Authors: Jason Getzler and Dr. Gail Richmond

Published: October 2, 2017

The critical transition from reactants to products occurs in less than a picosecond (10-12 s). Using an ultrafast femtosecond laser (10-15s), it is possible to further understand particle motion before, during, and after the chemical reaction transition. In this study, triiodide (𝐼3−), a simply-structured ion often used because of its stability and efficiency, was subjected to femtosecond laser pulses (NIR and UV wavelengths) to analyze the molecular photodissociation dynamics on an ultrashort time scale (10-12 seconds or shorter). First, vibrational oscillations from diidoide previously reported were replicated via pump-probe spectroscopy to confirm validity of experimentation model. This was followed by innovative pulse shaping techniques to maximize peak oscillations produced by molecules. Oscillation periods were statistically analyzed to understand the dynamics (the movement and vibrations of molecules) undergone by the 𝐼3−, over increased time delay. It was demonstrated that vibrational oscillations in triiodide solution, when subjected to UV pulse shaping using the MIIPS system, show a ±1.0E2 variance in optimal parameters for maximized oscillatory amplitudes and undergo cooling effects as the reaction ensues. Taken together, these observations shed new light on the application of the theoretical laws of quantum mechanics in describing the experimental dynamics of diiodide and that excited-state diiodide oscillations can be controlled by UV light to potentially undergo wavepacket focusing in the product channel of chemical reactions.

Keywords: Femtosecond chemistry, Pump-probe spectroscopy, pulse shaping, triiodide, diiodide, photodissocation, product channel