1
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Garg D, Chopra P, Lee JWL, Tikhonov DS, Kumar S, Akcaalan O, Allum F, Boll R, Butler AA, Erk B, Gougoula E, Gruet SP, He L, Heathcote D, Jones E, Kazemi MM, Lahl J, Lemmens AK, Liu Z, Loru D, Maclot S, Mason R, Merrick J, Müller E, Mullins T, Papadopoulou CC, Passow C, Peschel J, Plach M, Ramm D, Robertson P, Rompotis D, Simao A, Steber AL, Tajalli A, Tul-Noor A, Vadassery N, Vinklárek IS, Techert S, Küpper J, Rijs AM, Rolles D, Brouard M, Bari S, Eng-Johnsson P, Vallance C, Burt M, Manschwetus B, Schnell M. Ultrafast dynamics of fluorene initiated by highly intense laser fields. Phys Chem Chem Phys 2024. [PMID: 38958416 DOI: 10.1039/d3cp05063g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
We present an investigation of the ultrafast dynamics of the polycyclic aromatic hydrocarbon fluorene initiated by an intense femtosecond near-infrared laser pulse (810 nm) and probed by a weak visible pulse (405 nm). Using a multichannel detection scheme (mass spectra, electron and ion velocity-map imaging), we provide a full disentanglement of the complex dynamics of the vibronically excited parent molecule, its excited ionic states, and fragments. We observed various channels resulting from the strong-field ionization regime. In particular, we observed the formation of the unstable tetracation of fluorene, above-threshold ionization features in the photoelectron spectra, and evidence of ubiquitous secondary fragmentation. We produced a global fit of all observed time-dependent photoelectron and photoion channels. This global fit includes four parent ions extracted from the mass spectra, 15 kinetic-energy-resolved ionic fragments extracted from ion velocity map imaging, and five photoelectron channels obtained from electron velocity map imaging. The fit allowed for the extraction of 60 lifetimes of various metastable photoinduced intermediates.
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Affiliation(s)
- Diksha Garg
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- Department of Physics, Universität Hamburg, Hamburg, Germany
| | - Pragya Chopra
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- Institute of Physical Chemistry, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Jason W L Lee
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | | | - Sonu Kumar
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- Department of Physics, Universität Hamburg, Hamburg, Germany
| | | | - Felix Allum
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | | | - Alexander A Butler
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Benjamin Erk
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Eva Gougoula
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | | | - Lanhai He
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Germany
| | - David Heathcote
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Ellen Jones
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Mehdi M Kazemi
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Jan Lahl
- Department of Physics, Lund University, Lund, Sweden
| | - Alexander K Lemmens
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Amsterdam, The Netherlands
- FELIX Laboratory, Radboud University, Nijmegen, The Netherlands
| | - Zhihao Liu
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Donatella Loru
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | | | - Robert Mason
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - James Merrick
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Erland Müller
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Terry Mullins
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Germany
- European XFEL, Schenefeld, Germany
| | | | | | | | - Marius Plach
- Department of Physics, Lund University, Lund, Sweden
| | - Daniel Ramm
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Patrick Robertson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Dimitrios Rompotis
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- European XFEL, Schenefeld, Germany
| | - Alcides Simao
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | | | - Ayhan Tajalli
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Atia Tul-Noor
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Nidin Vadassery
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Germany
- Department of Chemistry, Universität Hamburg, Hamburg, Germany
| | - Ivo S Vinklárek
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Germany
| | - Simone Techert
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
| | - Jochen Küpper
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Germany
- Department of Physics, Universität Hamburg, Hamburg, Germany
- Center for Ultrafast Imaging, Universität Hamburg, Hamburg, Germany
- Department of Chemistry, Universität Hamburg, Hamburg, Germany
| | - Anouk M Rijs
- Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Daniel Rolles
- J. R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA
| | - Mark Brouard
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Sadia Bari
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands
| | | | - Claire Vallance
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | - Michael Burt
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, UK
| | | | - Melanie Schnell
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
- Institute of Physical Chemistry, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
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2
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Tikhonov DS, Lee JWL, Schnell M. On the thermodynamic stability of polycations. J Chem Phys 2024; 160:244110. [PMID: 38934634 DOI: 10.1063/5.0207526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
We present a simple approximation to estimate the largest charge that a given molecule can hold until fragmentation into smaller charged species becomes more energetically favorable. This approximation solely relies on the ionization potentials, electron affinities of the parent and fragment species, and also on the neutral parent's dissociation energy. By parameterizing these quantities, it is possible to obtain analytical phase diagrams of polycationic stability. We demonstrate the applicability of this approach by discussing the maximal charge dependence on the size of the molecular system. A numerical demonstration for linear polyenes, monocyclic annulenes, and helium clusters is provided.
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Affiliation(s)
- Denis S Tikhonov
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Jason W L Lee
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Melanie Schnell
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
- Institute of Physical Chemistry, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 1, 24118 Kiel, Germany
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3
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McManus JW, Allum F, Featherstone J, Lam CS, Brouard M. Two-Dimensional Projected-Momentum Covariance Mapping for Coulomb Explosion Imaging. J Phys Chem A 2024; 128:3220-3229. [PMID: 38607425 PMCID: PMC11056990 DOI: 10.1021/acs.jpca.4c01084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 03/28/2024] [Accepted: 03/29/2024] [Indexed: 04/13/2024]
Abstract
We introduce projected-momentum covariance mapping, an extension of recoil-frame covariance mapping for 2D ion imaging studies. By considering the two-dimensional projection of the ion momenta as recorded by the detector, one opens the door to a complex suite of analysis tools adapted from three-dimensional momentum imaging studies. This includes the use of different frames of reference to unravel the dynamics of fragmentation and the application of fragment momentum constraints to isolate specific fragmentation channels. The technique is demonstrated on data from a two-dimensional ion imaging study of the Coulomb explosion of the cis and trans isomers of 1,2-dichloroethene, following strong-field ionization by an intense near-infrared femtosecond laser pulse. Classical simulations are used to guide the interpretation of projected-momentum covariance maps. The results offer a detailed insight into the distinct Coulomb explosion dynamics for this pair of isomers and lay the groundwork for future time-resolved studies of photoisomerization dynamics in this molecular system.
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Affiliation(s)
- Joseph W. McManus
- Chemistry Research Laboratory,
Department of Chemistry, University of Oxford, Oxford OX1 3TA, U.K.
| | | | - Josh Featherstone
- Chemistry Research Laboratory,
Department of Chemistry, University of Oxford, Oxford OX1 3TA, U.K.
| | - Chow-Shing Lam
- Chemistry Research Laboratory,
Department of Chemistry, University of Oxford, Oxford OX1 3TA, U.K.
| | - Mark Brouard
- Chemistry Research Laboratory,
Department of Chemistry, University of Oxford, Oxford OX1 3TA, U.K.
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4
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van der Burgt PJM, Gradziel ML. Coincidence mass spectrometry study of double ionization of pyrene by 70 eV electron impact. Phys Chem Chem Phys 2024; 26:10688-10697. [PMID: 38511630 DOI: 10.1039/d4cp00443d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
We have performed coincidence mass spectrometry of fragmentation of pyrene molecules by 70 eV electron impact. Ionized fragments have been mass selected using a reflectron time-of-flight mass spectrometer, and a field programmable gate array has been used for the timing of the electron and ion extraction pulses and for the event-by-event detection of the ions. Double ionization results in a number of prominent fragmentations producing two singly-ionized fragments with kinetic energies of up to a few eV. A number of fragmentations produce ions with four or more carbon atoms, which can only be formed by the breaking of at least three C-C bonds.
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Affiliation(s)
- Peter J M van der Burgt
- Department of Experimental Physics, National University of Ireland Maynooth, Maynooth, Co, Kildare, Ireland.
| | - Marcin L Gradziel
- Department of Experimental Physics, National University of Ireland Maynooth, Maynooth, Co, Kildare, Ireland.
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5
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Atia-Tul-Noor, Kumar S, Schirmel N, Erk B, Manschwetus B, Alisaukas S, Braune M, Cirmi G, Czwalinna MK, Frühling U, Grosse-Wortmann U, Kschuev N, Kuschewski F, Lang T, Lindenblatt H, Litvinyuk I, Meister S, Moshammer R, Papadopoulou CC, Passow C, Roensch-Schulenburg J, Trost F, Hartl I, Düsterer S, Schulz S. Sub-50 fs temporal resolution in an FEL-optical laser pump-probe experiment at FLASH2. OPTICS EXPRESS 2024; 32:6597-6608. [PMID: 38439359 DOI: 10.1364/oe.513714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 01/18/2024] [Indexed: 03/06/2024]
Abstract
High temporal resolution is essential for ultra-fast pump-probe experiments. Arrival time jitter and drift measurements, as well as their control, become critical especially when combining XUV or X-ray free-electron lasers (FELs) with optical lasers due to the large scale of such facilities and their distinct pulse generation processes. This paper presents the application of a laser pulse arrival time monitor that actively corrects the arrival time of an optical laser relative to the FEL's main optical clock. Combined with post-analysis single pulse jitter correction this new approach improves the temporal resolution for pump-probe experiments significantly. Benchmark measurements on photo-ionization of xenon atoms performed at FLASH beamline FL26, demonstrate a sub-50 fs FWHM overall temporal resolution.
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6
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Milešević D, Popat D, Gellersen P, Liu Z, Stimson J, Robertson P, Green A, Vallance C. Design and characterization of an optical-fiber-coupled laser-induced desorption source for gas-phase dynamics experiments. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:114105. [PMID: 37987631 DOI: 10.1063/5.0170080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 11/03/2023] [Indexed: 11/22/2023]
Abstract
Preparation of neutral non-volatile molecules intact in the gas phase for mass spectrometry or chemical dynamics experiments remains a challenge for many classes of molecules. Here, we report the design and characterization of a fiber-coupled laser-based thermal desorption source capable of preparing intact neutral molecules at high molecular densities in the gas phase for use in velocity-map imaging experiments. Within this source, the sample is deposited onto a thin tantalum foil. Irradiation of the foil from the reverse side by a focused laser beam leads to highly localized heating of the sample, resulting in desorption of a plume of molecules into the gas phase. The fiber-coupled design simplifies the alignment of the desorption laser beam, and the ability to rotate the foil relative to the fixed laser beam allows the sample to be continually refreshed under vacuum. We use 118 nm photoionization of three test molecules-uracil, adenine, and phenylalanine-to characterize the source and to demonstrate various aspects of its performance. These include the dependence of the velocity-map imaging performance on the size of the interaction region and the dependence of the laser-induced desorption source emission on desorption laser power and heating time. Signal levels recorded in these measurements are comparable to those we typically obtain in similar experiments using a pulsed supersonic molecular beam, and we, therefore, believe that the source has considerable potential for use in a wide range of chemical dynamics and other experiments.
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Affiliation(s)
- Dennis Milešević
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Divya Popat
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Paul Gellersen
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Zhihao Liu
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Joseph Stimson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Patrick Robertson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Andrew Green
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
| | - Claire Vallance
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd., Oxford OX1 3TA, United Kingdom
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7
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Lee JWL, Stockett MH, Ashworth EK, Navarro Navarrete JE, Gougoula E, Garg D, Ji M, Zhu B, Indrajith S, Zettergren H, Schmidt HT, Bull JN. Cooling dynamics of energized naphthalene and azulene radical cations. J Chem Phys 2023; 158:2887564. [PMID: 37125715 DOI: 10.1063/5.0147456] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 04/12/2023] [Indexed: 05/02/2023] Open
Abstract
Naphthalene and azulene are isomeric polycyclic aromatic hydrocarbons (PAHs) and are topical in the context of astrochemistry due to the recent discovery of substituted naphthalenes in the Taurus Molecular Cloud-1 (TMC-1). Here, the thermal- and photo-induced isomerization, dissociation, and radiative cooling dynamics of energized (vibrationally hot) naphthalene (Np+) and azulene (Az+) radical cations, occurring over the microsecond to seconds timescale, are investigated using a cryogenic electrostatic ion storage ring, affording "molecular cloud in a box" conditions. Measurement of the cooling dynamics and kinetic energy release distributions for neutrals formed through dissociation, until several seconds after hot ion formation, are consistent with the establishment of a rapid (sub-microsecond) Np+ ⇌ Az+ quasi-equilibrium. Consequently, dissociation by C2H2-elimination proceeds predominantly through common Az+ decomposition pathways. Simulation of the isomerization, dissociation, recurrent fluorescence, and infrared cooling dynamics using a coupled master equation combined with high-level potential energy surface calculations [CCSD(T)/cc-pVTZ], reproduce the trends in the measurements. The data show that radiative cooling via recurrent fluorescence, predominately through the Np+ D0 ← D2 transition, efficiently quenches dissociation for vibrational energies up to ≈1 eV above dissociation thresholds. Our measurements support the suggestion that small cations, such as naphthalene, may be more abundant in space than previously thought. The strategy presented in this work could be extended to fingerprint the cooling dynamics of other PAH ions for which isomerization is predicted to precede dissociation.
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Affiliation(s)
- Jason W L Lee
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Mark H Stockett
- Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Eleanor K Ashworth
- School of Chemistry, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | | | - Eva Gougoula
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Diksha Garg
- Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - MingChao Ji
- Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Boxing Zhu
- Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
| | | | | | - Henning T Schmidt
- Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
| | - James N Bull
- School of Chemistry, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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8
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Mazza F, Thornquist O, Castellanos L, Butterworth T, Richard C, Boudon V, Bohlin A. The ro-vibrational ν 2 mode spectrum of methane investigated by ultrabroadband coherent Raman spectroscopy. J Chem Phys 2023; 158:094201. [PMID: 36889980 DOI: 10.1063/5.0138803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm-1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, ΔJ = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.
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Affiliation(s)
- Francesco Mazza
- Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
| | - Ona Thornquist
- Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
| | - Leonardo Castellanos
- Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
| | - Thomas Butterworth
- Faculty of Science and Engineering, Maastricht University, Paul Henri Spaaklaan 1, 6229 GS Maastricht, The Netherlands
| | - Cyril Richard
- Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - Vincent Boudon
- Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université Bourgogne Franche-Comté, 9 Avenue Alain Savary, BP 47 870, F-21078 Dijon Cedex, France
| | - Alexis Bohlin
- Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
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9
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Heathcote D, Robertson PA, Butler AA, Ridley C, Lomas J, Buffett MM, Bell M, Vallance C. Electron-induced dissociation dynamics studied using covariance-map imaging. Faraday Discuss 2022; 238:682-699. [PMID: 35781475 DOI: 10.1039/d2fd00033d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Recently, covariance analysis has found significant use in the field of chemical reaction dynamics. When coupled with data from product time-of-flight mass spectrometry and/or multi-mass velocity-map imaging, it allows us to uncover correlations between two or more ions formed from the same parent molecule. While the approach has parallels with coincidence measurements, covariance analysis allows experiments to be performed at much higher count rates than traditional coincidence methods. We report results from electron-molecule crossed-beam experiments, in which covariance analysis is used to elucidate the dissociation dynamics of multiply-charged ions formed by electron ionisation over the energy range from 50 to 300 eV. The approach is able to isolate signal contributions from multiply charged ions even against a very large 'background' of signal arising from dissociation of singly-charged parent ions. Covariance between the product time-of-flight spectra identifies pairs of fragments arising from the same parent ions, while covariances between the velocity-map images ('recoil-frame covariances') reveal the relative velocity distributions of the ion pairs. We show that recoil-frame covariance analysis can be used to distinguish between multiple plausible dissociation mechanisms, including multi-step processes, and that the approach becomes particularly powerful when investigating the fragmentation dynamics of larger molecules with a higher number of possible fragmentation pathways.
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Affiliation(s)
- David Heathcote
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Patrick A Robertson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Alexander A Butler
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Cian Ridley
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - James Lomas
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Madeline M Buffett
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Megan Bell
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
| | - Claire Vallance
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.
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10
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Vacher M, Boyer A, Loriot V, Lépine F, Nandi S. Few-Femtosecond Isotope Effect in Polyatomic Molecules Ionized by Extreme Ultraviolet Attosecond Pulse Trains. J Phys Chem A 2022; 126:5692-5701. [PMID: 35994358 DOI: 10.1021/acs.jpca.2c03487] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Following ionization by an extreme ultraviolet (XUV) attosecond pulse train, a polyatomic molecule can be promoted to more-than-one excited states of the residual ion. The ensuing relaxation dynamics is often facilitated by several reaction coordinates, making them difficult to disentangle by the usual spectroscopic means. Here, we show that in atto-chemistry isotope labeling can be an efficient tool for unraveling the relaxation pathways in highly excited photoionized molecules. Employing an XUV pump pulse and a near-infrared probe pulse, we found the nuclear as well as coupled electron-nuclear dynamics in ethylene to be almost 40% faster compared to that of its deuterated counterpart. The findings, which are supported by advanced nonadiabatic dynamics calculations, led to the identification of the relevant nuclear coordinates controlling the relaxation. Our experiment highlights the relevance of ultrashort XUV pulses to capture the isotopic effect in few-femtosecond molecular photodynamics.
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Affiliation(s)
- Morgane Vacher
- Nantes Université, CNRS, CEISAM UMR 6230, F-44300 Nantes, France
| | - Alexie Boyer
- Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Vincent Loriot
- Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Franck Lépine
- Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
| | - Saikat Nandi
- Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France
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11
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Lacinbala O, Féraud G, Vincent J, Pino T. Aromatic and Acetylenic C-H or C-D Stretching Bands Anharmonicity Detection of Phenylacetylene by UV Laser-Induced Vibrational Emission. J Phys Chem A 2022; 126:4891-4901. [PMID: 35880827 DOI: 10.1021/acs.jpca.2c01436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The anharmonic infrared (IR) emission spectra of phenylacetylene C6H5CCH and an isotopologue C6H5CCD induced by 193 nm UV excitation have been investigated in the gas phase. The study has been operated with a homemade IR spectrometer enabling to record time- and wavelength-resolved spectra between 2.5 and 4.5 μm, emitted all along the collisional cooling. The analysis is supported by a kinetic Monte Carlo simulation in the vibrational harmonic approximation. For both species, the anharmonic shifts of the acetylenic C-H or C-D stretching modes and the aromatic C-H stretching modes are studied for band positions and bandwidths in terms of the internal energy. For C6H5CCD, the internal energy dependence of the emission intensity band ratio is investigated and rationalized. This work demonstrates the potential of time-resolved IR emission spectroscopy to explore anharmonicity of astrophysically relevant molecules.
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Affiliation(s)
- Ozan Lacinbala
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Géraldine Féraud
- CNRS, LERMA, Sorbonne Université, Observatoire de Paris, Université PSL, F-75005, Paris, France
| | - Julien Vincent
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Thomas Pino
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
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