Resolving Molecular Electron Dynamics with Attosecond Spectroscopy Using Visible Light

Photoionization is a fundamental process in the interaction between light and matter. Our work aims to study ultrafast electron dynamics through photoionization of molecules and resolve the resulting multielectron dynamics. In attosecond spectroscopy of molecules, ionization by a high-harmonic generation (HHG) source using a conventional near-infrared (NIR) laser produces electrons from different energy states that overlap with each other, which makes it difficult to resolve each state. The overlap is due to the close spacing of high-harmonics produced from a NIR laser, and the complex structure of molecules which creates closely spaced ionization potentials for different states. In our work, we generate attosecond pulses using visible light with the wavelength of 400nm. With this wavelength, we have greater spectral separation between neighboring high harmonics as well as adequate high-harmonic flux. By using the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) method, we can retrieve the photoionization delay in the target molecule. The outgoing electron can also experience an effective potential by multielectron dynamics, modifying the photoionization delay. By measuring both the amplitude and phase of photoionization, we can resolve dynamic processes in molecules such as shape resonances. Here we present photoionization measurements in CO2 using attosecond pulses generated by visible light.