Control of ultrafast molecular photodissociation by laser-field-induced potentials

Abstract

Experiments aimed at understanding ultrafast molecular processes are now routine, and the notion that external laser fields can constitute an additional reagent is also well established. The possibility of externally controlling a reaction with radiation increases immensely when its intensity is sufficiently high to distort the potential energy surfaces at which chemists conceptualize reactions take place. Here we explore the transition from the weak- to the strong-field regimes of laser control for the dissociation of a polyatomic molecule, methyl iodide. The control over the yield of the photodissociation reaction proceeds through the creation of a light-induced conical intersection. The control of the velocity of the product fragments requires external fields with both high intensities and short durations. This is because the mechanism by which control is exerted involves modulating the potentials around the light-induced conical intersection, that is, creating light-induced potentials.

Chemical reactions induced by oscillating external fields in weak thermal environments

“…These interactions lead to emergent and controllable behavior in assembly phenomena, [27][28][29][30] organic synthesis, 31 protein folding, 32 the detection of DNA, 33 and photodissociation. 34 Knowledge of the mechanism by which these interactions mediate reactive flow provides a methodological tool in the design of molecular devices with unique functionality. [35][36][37] Materials that undergo conformational changes in response to an external trigger offer examples of such emergent technology.…”

Molecular events in the light of strong fields: A light‐induced potential scenario

“…However, recent experiments have shown that it is possible to achieve unprecedented control over photodissociation reactions. [8][9][10] . The LIPs provide a new playground where essentially new electronic states are created and these new chemical species are an open door to control the chemistry of simple molecules or to increase our understanding of the molecular dynamics in excited states.…”

“…Then the energy differences between V a e ðRÞ and the molecular potentials V 1 ðRÞ and V 2 ðRÞ at the time of the sudden switch off of S ðtÞ will be imprinted in the final KEDs. [10] …”

“…[109] Although most proposals remain experimentally untested, owing to the difficulty of finding good molecular systems where the strong field interaction is strong enough to generate LIPs, yet not too strong that the ionization is predominant, recent experiments have shown that indeed such control is possible. [8][9][10] In this work, we will review some of our findings. In LightInduced Potentials: Geometrical and Dynamical Features Section, we will provide a simplified analysis of the geometrical and dynamical features of LIPs, outlining the role of the Starkshift and of laser-induced potential energy shaping in several control scenarios.…”

“…[7] More recently, the non-resonant strong-field interaction of the pulse provided a means to alter the potential energy surface of the molecule via dynamic Stark effect, "catalyzing" many photochemical processes. [8][9][10][11] While all the previous roles remain useful for different purposes, one can arguably follow this sequence of events as one in which the laser is promoted from the role of a non-specific exciter (and probe of the chemical process), to a reactant and then to a catalyst, using the chemical terminology. In this review, we will outline some of our contributions in the control of molecules in the strong-field regime from a theoretical perspective.…”