Tracing nuclear-wave-packet dynamics in singly and doubly charged states of N${}_{2}$ and O${}_{2}$ with XUV-pump--XUV-probe experiments

Tracing nuclear-wave-packet dynamics in singly and doubly charged states of N $_{2}$ and O $_{2}$ with XUV-pump–XUV-probe experiments

M. Magrakvelidze, O. Herrwerth, Y. H. Jiang, A. Rudenko, M. Kurka, L. Foucar, K. U. Kühnel, M. Kübel, Nora G. Johnson, C. D. Schröter, S. Düsterer, R. Treusch, M. Lezius, I. Ben-Itzhak, R. Moshammer, J. Ullrich, M. F. Kling, and U. Thumm

Phys. Rev. A 86, 013415 – Published 18 July 2012

Abstract

We traced the femtosecond nuclear-wave-packet dynamics in ionic states of oxygen and nitrogen diatomic molecules employing 38-eV XUV-pump–XUV-probe experiments at the free-electron laser in Hamburg (FLASH). The nuclear dynamics is monitored via the detection of coincident ionic fragments using a reaction microscope and a split-mirror setup to generate the pump and probe pulses. By comparing measured kinetic-energy-release spectra with classical and quantum-mechanical simulations, we identified electronic states of the molecular ions that are populated by ionization of the neutral molecule. For specific fragment charge states, this comparison allows us to assess the relevance of specific dissociation paths.

Received 8 March 2012

DOI:https://doi.org/10.1103/PhysRevA.86.013415

Authors & Affiliations

M. Magrakvelidze¹, O. Herrwerth², Y. H. Jiang³, A. Rudenko^1,4,5, M. Kurka⁵, L. Foucar⁴, K. U. Kühnel⁵, M. Kübel², Nora G. Johnson^1,2, C. D. Schröter⁵, S. Düsterer⁶, R. Treusch⁶, M. Lezius², I. Ben-Itzhak¹, R. Moshammer⁵, J. Ullrich^4,5,7, M. F. Kling^1,2,*, and U. Thumm^1,†

¹J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA
²Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany
³Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
⁴Max-Planck Advanced Study Group at CFEL, 22607 Hamburg, Germany
⁵Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany
⁶DESY, 22607 Hamburg, Germany
⁷Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany

^*matthias.kling@mpq.mpg.de
^†thumm@phys.ksu.edu

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Vol. 86, Iss. 1 — July 2012

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Images

Figure 1
Adiabatic electronic states for (a) neutral O $_{2}$ and the O $_{2}^{+}$ , and (b) the O $_{2}^{2 +}$ molecular ion adapted from [26, 31, 32]. Gerade states are indicated as dashed lines and ungerade states as solid lines. The repulsive 1/ $R$ Coulomb potential, shifted to match the 39.0 eV dissociation limit, is shown as a dotted line. Dissociation limits are indicated to the right of the potential curves.Reuse & Permissions
Figure 2
Measured KER spectra as a function of the pump-probe delay τ (same logarithmic color/gray scale for the fragment yield in all plots) compared with the classically calculated KER curves K(τ) for different breakup channels: (a) O $^{+}$ +O $^{+}$ , (b) O $^{2 +}$ +O $^{+}$ , and (c) O $^{2 +}$ +O $^{2 +}$ . The delay-integrated KER spectra are shown on the left. The classical calculations were done using the dissociative $f$ $^{4} Π_{g}$ , $c$ $^{4} Σ_{u}$ $^{-}$ , $^{4} Π_{u}$ , and bound $a$ $^{4} Π_{u}$ states of O $_{2}^{+}$ and the dissociative $A$ $^{3} Σ_{u}^{+}$ and the bound 1 $^{1} Δ_{u}$ states of O $_{2}^{2 +}$ .Reuse & Permissions
Figure 3
(a) Measured KER spectra as a function of pump-probe delay τ for the O $_{2}$ → O $^{+}$ +O $^{+}$ breakup channel and (d, g) corresponding quantum-mechanical calculations. (b) Measured KER spectra for the O $_{2}$ → O $^{2 +}$ +O $^{+}$ channel and (e, h) corresponding quantum-mechanical calculations. (c) Measured KER spectra for the O $_{2}$ → O $^{2 +}$ +O $^{2 +}$ breakup channel and (f, i) corresponding quantum-mechanical calculations (same logarithmic color/gray scales for the fragment yield within each column). The dissociation bands are marked “D” (see text). The measured KER spectra are taken from Fig. 2 for positive delays and shown on a slightly different color/gray scale, as indicated. The inset in panel (i) shows the calculated KER for the dissociative intermediate state O $_{2}^{2 +}$ ( $A$ $^{3} Σ_{u}^{+}$ ).Reuse & Permissions
Figure 4
Adiabatic electronic states for (a) neutral N $_{2}$ and the N $_{2}^{+}$ , and (b) the N $_{2}^{2 +}$ molecular ion adapted from [26, 31, 32]. Gerade states are indicated as dashed lines and ungerade states as solid lines. The repulsive 1/ $R$ Coulomb potential, shifted to match the 38.9 eV dissociation limit, is shown as a dotted line. Dissociation limits are indicated to the right of the potential curves.Reuse & Permissions
Figure 5
Measured KER spectra as a function of pump-probe delay τ (same logarithmic color/gray scale for the fragment yield in all plots) compared with the classically calculated KER curves K(τ) for different breakup channels: (a) N $^{+}$ +N $^{+}$ , (b) N $^{2 +}$ +N $^{+}$ , and (c) N $^{2 +}$ +N $^{2 +}$ . The delay-integrated KER spectra are shown on the left. The classical calculations were done for the dissociative 2 $^{2} Σ_{u}$ , 2 $^{2} Π_{u}$ , 3 $^{2} Π_{u}$ , 3 $^{2} Σ_{g}$ , 4 $^{2} Π_{u}$ , 4 $^{2} Σ_{u}$ , 5 $^{2} Π_{u}$ , and the bound $B$ $^{2} Σ_{u}^{+}$ states of N $_{2}^{+}$ and the dissociative $a$ $^{3} Π_{u}$ and bound $D$ $^{3} Σ_{u}^{+}$ states of N $_{2}^{2 +}$ .Reuse & Permissions
Figure 6
(a) Measured KER spectra as a function of pump-probe delay τ for the N $_{2}$ → N $^{+}$ +N $^{+}$ breakup channel and (d, g) corresponding quantum-mechanical calculations. (b) Measured KER spectra for the N $_{2}$ → N $^{2 +}$ +N $^{+}$ channel and (e, h) corresponding quantum-mechanical calculations. (c) Measured KER spectra for the N $_{2}$ → N $^{2 +}$ +N $^{2 +}$ breakup channel and (f, i) corresponding quantum-mechanical calculations (same logarithmic color/gray scales for the fragment yield within each column). The measured KER spectra are taken from Fig. 2 for positive delays and shown on a different color/gray scale, as indicated.Reuse & Permissions

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