Two-photon excited state dynamics of dark valence, rydberg, and superexcited states in 1,3-butadiene

Abstract

Two-photon absorption in systems with parity permits access to states that cannot be prepared by one-photon absorption. Here we present the first time-resolved photoelectron spectroscopy study using this technique, applied to 1,3-butadiene, in which we investigated the dynamics of its dark valence, Rydberg, and superexcited states. The dark valence state dynamics are accessed via the Rydberg manifold, excited by two photons of 400 nm. We find that the 'dark' 21Ag state populated in this manner has a much longer lifetime than when accesses via the 11Bu 'bright' valence state when populated by one photon of 200 nm. In addition, we compared the dynamics of the 3s\u3c0- and 3d\u3c0-Rydberg states. These Rydberg states relax to the valence manifold on a subpicosecond time scale, with the 3s\u3c0-Rydberg state decay rate being larger due to a stronger valence-Rydberg mixing. Finally, we investigated superexcited valence states that fragment or autoionize within 200 fs, likely without involving Rydberg states.Peer reviewed: YesNRC publication: Ye