# Geometrical optimization approach to isomerization: Models and limitations

## TL;DR

This paper applies a geometrical optimization method to laser-driven isomerization reactions, analyzing how symmetry-induced restrictions affect the ability to enhance reaction yields using optimized initial states and pulse sequences.

## Contribution

It demonstrates the application of a geometrical optimization approach to model and understand limitations in laser-driven isomerization, including the necessity of pump-dump mechanisms.

## Key findings

- Long pulses can induce isomerization with a single pulse.
- Phase of initial superposition does not influence yield.
- Short pulses require a pair of pulses for effective isomerization.

## Abstract

We study laser-driven isomerization reactions through an excited electronic state using the recently developed Geometrical Optimization procedure [J. Phys. Chem. Lett. 6, 1724 (2015)]. The goal is to analyze whether an initial wave packet in the ground state, with optimized amplitudes and phases, can be used to enhance the yield of the reaction at faster rates, exploring how the geometrical restrictions induced by the symmetry of the system impose limitations in the optimization procedure. As an example we model the isomerization in an oriented 2,2'-dimethyl biphenyl molecule with a simple quartic potential. Using long (picosecond) pulses we find that the isomerization can be achieved driven by a single pulse. The phase of the initial superposition state does not affect the yield. However, using short (femtosecond) pulses, one always needs a pair of pulses to force the reaction. High yields can only be obtained by optimizing both the initial state, and the wave packet prepared in the excited state, implying the well known pump-dump mechanism.