Tracing few-femtosecond photodissociation dynamics on molecular oxygen with a single-color pump-probe scheme in the VUV

Abstract

Molecular wave-packet dynamics in oxygen are studied in the time domain, using a single-color VUVpump-VUV-probe scheme. 17-fs VUV pulses, centered at 161 nm are generated via high-order harmonic generation driven by an intense 800-nm pulse leading to VUV pulse energies that reach 1.1 μJ per pulse. An all-reflective interferometric pump-probe scheme is used for studying the delay dependence of the molecular oxygen ion signal with simultaneous nonresonant photoionization of krypton as a precise timing-reference. Access to the excited dissociative state lifetime is provided by the resulting delay-dependent O 2 + signal, ultimately limited by the molecular ionization window. The ability to use a two-photon VUV probe provides the delay-dependent detection of O + as an additional observable, extending the dissociation observation window.

Time-Resolved Dissociation Dynamics of Iodomethane Resulting from Rydberg and Valence Excitation

“…Relevant ionic states, as well as a window indicated by the blue double arrows, are shown in Figure 1b. Similarly as in our study 40 of the VUV-induced dissociation dynamics of O 2 , this pathway extends the parent species' ionization window, which is in accordance with dissociation through the 2 1 A 1 state.…”

“…The sub-21 fs harmonic pulses grant the required temporal resolution to study dynamics in the sub-10 fs range and follow the processes steering the reaction dynamics directly after the excitation. , While resonance-enhanced multiphoton ionization (REMPI) schemes allow interrogating individual dissociation pathways, the excitation scheme utilized here can be applied readily to a wide range of molecules. The weak-field VUV-probe avoids light-induced effects on the molecular potential energy landscape. , When multiphoton IR probe ionization is used instead, great care has to be taken to evaluate the relevance and impact of these effects .…”

Weak-field few-femtosecond VUV photodissociation dynamics of water isotopologues

“…This VUV pump-probe approach complements previous studies relying on multiphoton ionization in the probe step, where a sufficiently high infrared field strength is needed. These strong fields may influence the molecular potentials [25] and affect the intrinsic molecular dynamics, as discussed in our previous study on the photodissociation of O 2 [26]. In our weak-field approach these effects, as well as the influence of intermediate states, which might be accessed resonantly in the probe step, are excluded, allowing a simplified theoretical description of the experimental observables for the molecular dynamics.…”