XUV-Initiated Dissociation Dynamics of Molecular Oxygen (O2)

Marc Rebholz,Christian Ott,Patrick Rupprecht,Thomas Ding,Lennart Aufleger,Marco Butz,Thomas Pfeifer,Gergana Dimitrova Borisova,Günter Brenner,David Wachs,Veit Stooß,Alexander Magunia,Carina Da Costa Castanheira,Kristina Meyer,Maia Magrakvelidze,Yonghao Mi,Paul Birk,Uwe Thumm,Maximilian Hartmann ,H Zacharias ,Sebastian Roling ,R Treusch ,S Düsterer

doi:10.1021/acs.jpca.1c06033

Abstract

We performed a time-resolved spectroscopy experiment on the dissociation of oxygen molecules after the interaction with intense extreme-ultraviolet (XUV) light from the free-electron laser in Hamburg at Deutsches Elektronen-Synchrotron. Using an XUV-pump/XUV-probe transient-absorption geometry with a split-and-delay unit, we observe the onset of electronic transitions in the O2+ cation near 50 eV photon energy, marking the end of the progression from a molecule to two isolated atoms. We observe two different time scales of 290 ± 53 and 180 ± 76 fs for the emergence of different ionic transitions, indicating different dissociation pathways taken by the departing oxygen atoms. With regard to the emerging opportunities of tuning the central frequencies of pump and probe pulses and of increasing the probe–pulse bandwidth, future pump–probe transient-absorption experiments are expected to provide a detailed view of the coupled nuclear and electronic dynamics during molecular dissociation.

Highlights

Oxygen plays a central role in the metabolism of many life forms on earth[1] as well as in combustion processes.[2]it shields the earth from ultraviolet radiation in the form of the ozone layer.[3]In addition to its fundamental importance, as a diatomic molecule, oxygen can serve as a model system for the experimental and theoretical study of nuclear wave-packet dynamics.[4−7] In recent years, such experiments have mostly been conducted using few-cycle near-infrared (NIR) laser pulses in time-resolved pump−probe spectroscopy studies.[6−9] the intense electric field of the NIR pulses introduces strong couplings between individual electronic states
The measured quantity in the presented transient absorption study is the spectrum of the free-electron lasers (FELs) probe pulse transmitted through an oxygen gas sample
With a spectral resolution of ∼35 meV at 50 eV we have identified several transitions in O2+ with different initial-state electronic configurations, which exponentially rise with different time scales

Summary

Introduction

Oxygen plays a central role in the metabolism of many life forms on earth[1] as well as in combustion processes.[2]it shields the earth from ultraviolet radiation in the form of the ozone layer.[3]In addition to its fundamental importance, as a diatomic molecule, oxygen can serve as a model system for the experimental and theoretical study of nuclear wave-packet dynamics.[4−7] In recent years, such experiments have mostly been conducted using few-cycle near-infrared (NIR) laser pulses in time-resolved pump−probe spectroscopy studies.[6−9] the intense electric field of the NIR pulses introduces strong couplings between individual electronic states. Oxygen plays a central role in the metabolism of many life forms on earth[1] as well as in combustion processes.[2]. It shields the earth from ultraviolet radiation in the form of the ozone layer.[3]. In addition to its fundamental importance, as a diatomic molecule, oxygen can serve as a model system for the experimental and theoretical study of nuclear wave-packet dynamics.[4−7] In recent years, such experiments have mostly been conducted using few-cycle near-infrared (NIR) laser pulses in time-resolved pump−probe spectroscopy studies.[6−9] the intense electric field of the NIR pulses introduces strong couplings between individual electronic states. The introduction of extreme ultraviolet (XUV) free-electron lasers (FELs)[10] as intense sources of XUV radiation made XUV-pump−XUV-probe schemes possible.

Results

Discussion

Conclusion