Probing molecular autoionization and dissociation using photoelectron spectroscopy

We studied the ultrafast dynamics of Rydberg states of polyatomic molecules near conical intersection using differential pump-probe photoelectron spectroscopy and Raman electron interferometry. Attosecond XUV pump was used to excite the carbon dioxide molecule to the Rydberg states above the first ionization threshold. While participating in conical intersection dynamics, these Rydberg states can undergo neutral predissociation or they can autoionize to lower lying continuum thresholds of the molecule with a very different evolution timescale. The competition between neutral predissociation and autoionization is studied using a second time delayed infrared probe that can further ionize the molecular Rydberg states as well as their dissociated fragments to their continuum limit. Velocity map imaging spectrometer was used to collect the photoelectrons generated by Rydberg autoionization and IR induced photoionization. From the differential photoelectron signal and Raman interferences we obtain both high spectral and temporal resolution to monitor the autoionizing wavepacket dynamics, allowing us to extract autoionization and dissociation lifetimes.