Role of proton dynamics in efficient photoionization of hydrocarbon molecules

Xinhua Xie, Stefan Roither, Markus Schöffler, Huailiang Xu, Sergiy Bubin, Erik Lötstedt, Sonia Erattuphuza, Atsushi Iwasaki, Daniil Kartashov, Kálmán Varga, Gerhard G. Paulus, Andrius Baltuška, Kaoru Yamanouchi, and Markus Kitzler
Phys. Rev. A 89, 023429 – Published 26 February 2014

Abstract

We experimentally investigate the ionization mechanism behind the formation of remarkably high charge states observed in the laser-pulse-induced fragmentation of different hydrocarbon molecules by Roither et al. [Phys. Rev. Lett. 106, 163001 (2011)], who suggested enhanced ionization occurring at multiple C-H bonds as the underlying ionization mechanism. Using multiparticle coincidence momentum imaging we measure the yield of multiply charged fragmenting ethylene and acetylene molecules at several intensities and pulse durations ranging from the few-cycle regime to 25 fs. We observe, at constant intensity, a strong increase of the proton energy with increasing laser pulse duration. It is shown that this is caused by a strong increase in the yield of highly charged parent molecular ions with pulse duration. Based on experimental evidence we explain this increase by the necessary population of precursor states in the parent ion that feature fast C-H stretch dynamics to the critical internuclear distance, where efficient ionization via enhanced ionization takes place. For increasing pulse duration these precursor ionic states are more efficiently populated, which leads in turn to a higher enhanced-ionization probability for longer pulses. Our work provides experimental evidence for the existence of a multiple-bond version of enhanced ionization in polyatomic molecules.

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  • Received 23 October 2013
  • Revised 21 January 2014

DOI:https://doi.org/10.1103/PhysRevA.89.023429

©2014 American Physical Society

Authors & Affiliations

Xinhua Xie1, Stefan Roither1, Markus Schöffler1, Huailiang Xu1,2, Sergiy Bubin3, Erik Lötstedt4,5, Sonia Erattuphuza1, Atsushi Iwasaki4, Daniil Kartashov1, Kálmán Varga6, Gerhard G. Paulus7,8, Andrius Baltuška1, Kaoru Yamanouchi4, and Markus Kitzler1,*

  • 1Photonics Institute, Vienna University of Technology, A-1040 Vienna, Austria, EU
  • 2State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
  • 3Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
  • 4Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan
  • 5Laser Technology Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
  • 6Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
  • 7Institute of Optics and Quantum Electronics, Friedrich-Schiller-University Jena, D-07743 Jena, Germany, EU
  • 8Helmholtz Institute Jena, D-07743 Jena, Germany, EU

  • *markus.kitzler@tuwien.ac.at

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Vol. 89, Iss. 2 — February 2014

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