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Treiber L, Kanya R, Kitzler-Zeiler M, Koch M. Dynamics of Above-Threshold Ionization and Laser-Assisted Electron Scattering inside Helium Nanodroplets. J Phys Chem A 2022; 126:8380-8387. [PMID: 36384271 PMCID: PMC9677425 DOI: 10.1021/acs.jpca.2c05410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
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Laser-assisted electron scattering (LAES) is a fundamental
three
body interaction process that enables energy transfer between electrons
and photons in the presence of matter. Here, we focus on the multiscattering
regime of electrons generated by above-threshold ionization (ATI)
of In atoms inside a high-density nanostructure, helium nanodroplets
(HeN) of ∼40 Å radius. The stochastic nature
of the multiscattering regime results in photoelectron spectra independent
of laser polarization. Numerical simulations via tunnel-type ionization
followed by applying the Kroll–Watson approximation for LAES
are in agreement with experimental spectra and yield a mechanistic
description of electron generation and the LAES energy modulation
processes. We find a negligible influence of the electron start position
inside the helium droplet on the simulated electron energy spectrum.
Further, our simulations shine light on the interplay of electron
time of birth, number of LAES gain/loss events, and final kinetic
energy; early ionization leads to the largest number of scattering
events and thereby the highest electron kinetic energy.
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Affiliation(s)
- Leonhard Treiber
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010Graz, Austria
| | - Reika Kanya
- Department of Chemistry, Faculty of Science, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji-shi, Tokyo192-0397, Japan
- JST PRESTO, 1-1 minami-Osawa, Hachioji-shi, Tokyo192-0397, Japan
| | - Markus Kitzler-Zeiler
- Photonics Institute, Technische Universität Wien, Gusshausstrasse 27-29, 1040Vienna, Austria
| | - Markus Koch
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010Graz, Austria
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Vilà A, González M. Quantum dynamics of the Br 2 (B-excited state) photodissociation in superfluid helium nanodroplets: importance of the recombination process. Phys Chem Chem Phys 2022; 24:24353-24361. [PMID: 36178095 DOI: 10.1039/d2cp02984g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have studied the Br2 photodissociation dynamics (B ← X electronic transition) of Br2(v = 0, X)@(4He)N doped nanodroplets (T = 0.37 K) at zero angular momentum, with N in the 100-1000 interval. To do this, we have used a quantum mechanical hybrid strategy proposed by us and, as far as we know, this is the second quantum dynamics study available on the photodissociation of molecules in superfluid helium nanodroplets. While the results obtained for some properties are qualitatively similar to those reported previously by us for the Cl2(B ← X) related case (in particular, the oscillating Br final velocity distribution which also arises from quantum interferences), large differences are evident in three key properties: the photodissociation mechanism and probability and the time scale of the process. This can be interpreted on the basis of the significantly lower excitation energy achieved by the Br2(B ← X) transition and the higher reduced mass of Br-Br in comparison to the chlorine case. The Br2(B) photodissociation dynamics is significantly more complex than that of Cl2(B) and leads to the fragmentation of the initial wave packet. Thus, the probability of non-dissociation is equal to 17, 18, 51, 85 and 100% for N = 100, 200, 300, 500 and 1000, respectively, while for chlorine this probability is equal to zero. In spite of the very large experimental difficulties that exist for obtaining nanodroplets with a well defined size, we hope that these results will encourage experimentalists to investigate these interesting systems.
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Affiliation(s)
- Arnau Vilà
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
| | - Miguel González
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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Michiels R, Abu-Samha M, Madsen LB, Binz M, Bangert U, Bruder L, Duim R, Wituschek A, LaForge AC, Squibb RJ, Feifel R, Callegari C, Di Fraia M, Danailov M, Manfredda M, Plekan O, Prince KC, Rebernik P, Zangrando M, Stienkemeier F, Mudrich M. Enhancement of Above Threshold Ionization in Resonantly Excited Helium Nanodroplets. PHYSICAL REVIEW LETTERS 2021; 127:093201. [PMID: 34506185 DOI: 10.1103/physrevlett.127.093201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 06/05/2021] [Accepted: 07/15/2021] [Indexed: 06/13/2023]
Abstract
Clusters and nanodroplets hold the promise of enhancing high-order nonlinear optical effects due to their high local density. However, only moderate enhancement has been demonstrated to date. Here, we report the observation of energetic electrons generated by above-threshold ionization (ATI) of helium (He) nanodroplets which are resonantly excited by ultrashort extreme ultraviolet (XUV) free-electron laser pulses and subsequently ionized by near-infrared (NIR) or near-ultraviolet (UV) pulses. The electron emission due to high-order ATI is enhanced by several orders of magnitude compared with He atoms. The crucial dependence of the ATI intensities with the number of excitations in the droplets suggests a local collective enhancement effect.
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Affiliation(s)
- R Michiels
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - M Abu-Samha
- College of Engineering and Technology, American University of the Middle East, Egaila, Kuwait
| | - L B Madsen
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - M Binz
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - U Bangert
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - L Bruder
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - R Duim
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - A Wituschek
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - A C LaForge
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - R J Squibb
- Department of Physics, University of Gothenburg, 41296 Gothenburg, Sweden
| | - R Feifel
- Department of Physics, University of Gothenburg, 41296 Gothenburg, Sweden
| | - C Callegari
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - M Di Fraia
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - M Danailov
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - M Manfredda
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - O Plekan
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - K C Prince
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - P Rebernik
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
| | - M Zangrando
- Elettra-Sincrotrone Trieste S.C.p.A, 34149 Basovizza, Trieste, Italy
- IOM-CNR, 34149 Trieste, Italy
| | - F Stienkemeier
- Institute of Physics, University of Freiburg, 79104 Freiburg, Germany
| | - M Mudrich
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
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4
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Observation of laser-assisted electron scattering in superfluid helium. Nat Commun 2021; 12:4204. [PMID: 34244517 PMCID: PMC8270992 DOI: 10.1038/s41467-021-24479-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 06/18/2021] [Indexed: 11/08/2022] Open
Abstract
Laser-assisted electron scattering (LAES), a light-matter interaction process that facilitates energy transfer between strong light fields and free electrons, has so far been observed only in gas phase. Here we report on the observation of LAES at condensed phase particle densities, for which we create nano-structured systems consisting of a single atom or molecule surrounded by a superfluid He shell of variable thickness (32-340 Å). We observe that free electrons, generated by femtosecond strong-field ionization of the core particle, can gain several tens of photon energies due to multiple LAES processes within the liquid He shell. Supported by Monte Carlo 3D LAES and elastic scattering simulations, these results provide the first insight into the interplay of LAES energy gain/loss and dissipative electron movement in a liquid. Condensed-phase LAES creates new possibilities for space-time studies of solids and for real-time tracing of free electrons in liquids.
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