title: Time-resolved photoelectron imaging with a femtosecond vacuum-ultraviolet light source: Dynamics in the A∼/B∼- and F∼-bands of SO2.
abstract: Time-resolved photoelectron imaging is demonstrated using the third harmonic of a 400-nm femtosecond laser pulse as the ionization source. The resulting 133-nm pulses are combined with 266-nm pulses to study the excited-state dynamics in the A∼/B∼- and F∼-band regions of SO2. The photoelectron signal from the molecules excited to the A∼/B∼-band does not decay for at least several picoseconds, reflecting the population of bound states. The temporal variation of the photoelectron angular distribution (PAD) reflects the creation of a rotational wave packet in the excited state. In contrast, the photoelectron signal from molecules excited to the F∼-band decays with a time constant of 80 fs. This time constant is attributed to the motion of the excited-state wave packet out of the ionization window. The observed time-dependent PADs are consistent with the F∼ band corresponding to a Rydberg state of dominant s character. These results establish low-order harmonic generation as a promising tool for time-resolved photoelectron imaging of the excited-state dynamics of molecules, simultaneously giving access to low-lying electronic states, as well as Rydberg states, and avoiding the ionization of unexcited molecules.
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
authors.forename: Vít
authors.initials: V
authors.lastname: Svoboda
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
authors.forename: Niraghatam Bhargava
authors.initials: NB
authors.lastname: Ram
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
authors.forename: Rajendran
authors.initials: R
authors.lastname: Rajeev
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
authors.forename: Hans Jakob
authors.initials: HJ
authors.lastname: Wörner