Enhancement of strong-field multiple ionization in the vicinity of the conical intersection in 1,3-cyclohexadiene ring opening

TL;DR

This study demonstrates a significant increase in double ionization near a conical intersection during the ring-opening of 1,3-cyclohexadiene, linking electronic state degeneracy to ionization enhancement.

Contribution

It reveals the enhancement of strong-field double ionization specifically associated with conical intersections in polyatomic molecules.

Findings

Double ionization is enhanced near the conical intersection.

The enhancement correlates with the HOMO-LUMO degeneracy.

Ion kinetic energy measurements confirm the effect during ring opening.

Abstract

Nonradiative energy dissipation in electronically excited polyatomic molecules proceeds through conical intersections, loci of degeneracy between electronic states. We observe a marked enhancement of laser-induced double ionization in the vicinity of a conical intersection during a non-radiative transition. We measured double ionization by detecting the kinetic energy of ions released by laser-induced strong-field fragmentation during the ring-opening transition between 1,3-cyclohexadiene and 1,3,5-hexatriene. The enhancement of the double ionization correlates with the conical intersection between the HOMO and LUMO orbitals.