Title: Geometrical optimization approach to isomerization: Models and limitations,
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.