Ultrafast imaging of spontaneous symmetry breaking in a photoionized molecular system

Abstract The Jahn-Teller effect is an essential mechanism of spontaneous symmetry breaking in molecular and solid state systems, and has far-reaching consequences in many fields. Up to now, to direct image the onset of Jahn-Teller symmetry breaking remains unreached. Employing ultrafast ion-coincidence Coulomb explosion imaging with sub-10 fs resolution, we unambiguously imaged the ultrafast dynamics of Jahn-Teller deformations of CH4+ cation in real space. It is unraveled that the Jahn-Teller deformation from C3v to C2v geometries takes a characteristic time of about 20 femtoseconds for this system. Classical and quantum molecular dynamics simulations agree well with the measurement, and reveal dynamics for the build-up of the C2v structure involving complex phasing process of multiple vibrational pathways of the CH4+ cation.