Ultrafast restoration of valence electrons in 1,3-butadiene probed by time-resolved photoelectron spectroscopy with high harmonic pulses

High harmonics are a promising tool to investigate ultrafast phenomena in the femtosecond and attosecond temporal regions. Since the photon energies of high harmonics are high enough to ionize both valence and core electrons of molecules and solid materials, we can gain insight into the temporal evolution of the electronic structure after photoexcitation by time-resolved photoelectron spectroscopy using high harmonics. However, because the multiple orders of high harmonics copropagate, the application of high harmonics to photoelectron spectroscopy is not straightforward. Therefore, we developed a harmonic beamline, based on the time-delay compensated monochromator, selecting a single harmonic order with the preserved pulse duration [1].