Using attosecond high-harmonics to probe dynamics near conical intersections

Conical intersections provide a highly efficient means for electronic relaxation in excited polyatomic molecules. However, the experimental time-resolved studies of non-adiabatic couplings and dynamics associated with conical intersections have been limited. Here, we present the results of an attosecond, XUV pump - IR probe experiment to resolve the non-adiabatic dynamics of the CO$_2$ molecular ion in the vicinity of a conical intersection. We use 11th harmonic in the XUV pulse train to create a wavepacket in the two lowest excited states of CO$_2^+$. The IR pulse samples the evolution of this wavepacket and results in formation of O$^+$ and CO$^+$ ions along different dissociation pathways. We observe coherent oscillations in the fragmentation yield which can be attributed to the vibronic coupling mechanism of the conical intersection.