The role of the methyl ion in the fragmentation of CH<sub>4</sub><sup>2+</sup>

Flammini, R.; Satta, Mauro; Fainelli, E.; Alberti, G.; Maracci, F.; Avaldi, L.

doi:10.1088/1367-2630/11/8/083006

Cited by 29 publications

(26 citation statements)

References 40 publications

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“…The optimized geometries are given in table 1. These states were also calculated by Flammini et al [12], but the geometries they found at an apparently different level of MCSCF were somewhat different. However that work did show that the asymptotic energies of these states compared with the energies of the corresponding states of CH ++ 4 in T d symmetry suggested that there must be an intersection between the 1 E and 1 A 1 states which is the one visible in figure 8.…”

Section: Electronic Structure Calculations and The Identification Of mentioning

confidence: 64%

“…Such measurements are sometimes called recoil-frame photoelectron angular distributions (RFPADs) to distinguish them from the full MFPAD for the completely oriented molecule. These decay channels and many others have been studied before in experiments that observe the Auger electron in coincidence with the ionic fragments [10][11][12]. In this study we build particularly on the previous work of Kukk et al [10] The central question that determines if coincidence measurements in these channels yield information on the orientation of the molecule is whether or not the dissociation dynamics are prompt and the fragmentation occurs essentially along the directions of the bonds in the molecule.…”

Section: Introductionmentioning

confidence: 87%

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Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

Williams

Trevisan

Schöffler

et al. 2012

J. Phys. B: At. Mol. Opt. Phys.

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We present experimental measurements and theoretical calculations for the photoionization of CH 4 at the carbon K-edge. Measurements performed using cold target recoil ion momentum spectroscopy (COLTRIMS) combined with complex Kohn variational calculations of the photoelectron in the molecular frame demonstrate the surprising result that the low energy photoelectrons effectively image the molecule by emerging along the bond axes. Furthermore, we observe a dynamic breakdown of axial recoil behaviour in one of the dissociation pathways of the intermediate dication, which we interpret using electronic structure calculations.

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Section: Electronic Structure Calculations and The Identification Of mentioning

confidence: 64%

Section: Introductionmentioning

confidence: 87%

Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

Williams

Trevisan

Schöffler

et al. 2012

J. Phys. B: At. Mol. Opt. Phys.

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show abstract

“…The slope of the 1t −2 2 ( 1 A 1 ) potential-energy curve was also estimated independently based on the theoretical results of Flammini et al [23]. According to their analysis, the energy of this state in the ground-state geometry is 3.9 eV above a local minimum at an equilibrium distance of 1.32Å.…”

Section: Discussionmentioning

confidence: 99%

“…The dicationic states of this molecule, in particular the ground state, have attracted considerable interest. Methods for their investigation include Auger decay [13,14], charge stripping spectroscopy (see the critical review in [15]), double charge transfer [16][17][18], photoelectron-ion-ion coincidence spectroscopy [19], photoelectron-photoelectron coincidence spectroscopy [20], coincidence spectroscopy of Auger electrons and ions [21][22][23], and quantum chemical calculations [15,[23][24][25][26]. The four lowest dicationic states actually possess a potential-energy surface with a local minimum [23], i.e., CH 2+ 4 can be metastable.…”

Section: Introductionmentioning

confidence: 99%

Probing dissociative molecular dications by mapping vibrational wave functions

et al. 2011

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We present high-resolution photoelectron-Auger-electron coincidence spectra of methane (CH 4 ). Since the vibrational structure in the photoelectron spectrum is resolved, the Auger spectra corresponding to different vibrational levels can be separated. The seven final states of CH 2+ 4 are either dissociative or metastable, but in any case are populated in a repulsive part of their potential-energy curve via the Auger decay. The Auger line shapes can therefore be obtained by mapping the vibrational wave functions of the core-hole state into energy space. We have implemented this connection in the data analysis. By simultaneously fitting the different Auger spectra, detailed information on the energies of the dicationic states and their repulsive potential-energy curves is derived.

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“…Momentum imaging of those three fragments with the photoelectron in coincidence provides a direct and unambiguous measurement of the MFPAD for a polyatomic molecule through the simultaneous orientation of three axes for every ionization event detected. We demonstrate this concept here using K-shell photoionization [10] of the methane molecule as a prototype. We find the surprising result that, for photoelectron energies below about 10 eV, the photelectron tends to be focused along the bond directions, and that, when the MFPAD is averaged over all polarization directions, the result can effectively image the geometry of the molecule.…”

mentioning

confidence: 99%

Imaging Polyatomic Molecules in Three Dimensions Using Molecular Frame Photoelectron Angular Distributions

et al. 2012

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We demonstrate a method for determining the full three-dimensional molecular-frame photoelectron angular distribution in polyatomic molecules using methane as a prototype. Simultaneous double Auger decay and subsequent dissociation allow measurement of the initial momentum vectors of the ionic fragments and the photoelectron in coincidence, allowing full orientation by observing a three-ion decay pathway, (H þ , H þ , CH þ 2 ). We find the striking result that at low photoelectron energies the molecule is effectively imaged by the focusing of photoelectrons along bond directions. DOI: 10.1103/PhysRevLett.108.233002 PACS numbers: 33.80.Eh, 33.60.+q Imaging molecular structure is a critical challenge in chemical physics recently highlighted by the emergence of techniques that, similar to ultrafast electron diffraction [1] or x-ray diffraction [2], have the potential to be taken to the time domain and thereby ultimately be used to make ''movies'' of chemical reactions on their natural time scale. Of particular interest is the development of such techniques that can be applied to the dynamics of isolated molecules. Here, the full three-dimensional orientation of a polyatomic molecule is measured simultaneously with the three components of the momentum of a photoelectron ejected from it with no underlying assumptions of symmetry or geometry. We present three-dimensional images of a polyatomic molecule measured with this technique, demonstrating an effect predicted [3] for polyatomic molecules with a heavy central atom bonded to hydrogens, namely that low-energy photoelectrons can directly image the molecular potential and bond structure.When a photoelectron is launched by photoabsorption of an inner shell, the outgoing photoelectron wave is then scattered by the aggregate potential of the molecule. The final angular distribution in the body-fixed frame of the molecule is an exquisitely sensitive probe of molecular structure and initial electronic state, which has been recently argued and demonstrated [4,5]. However, observing molecular-frame photoelectron angular distributions (MFPADs) at high resolution requires accurate orientation of the molecule in the gas phase. Three-dimensional laser alignment [6,7] can accomplish such orientation prior to photoionization but is limited to molecules with an asymmetric polarizability. In the case of simple diatomic molecules, orientation can also be accomplished by detecting the photoelectron in coincidence with positively charged fragments that emerge following prompt Auger decay and dissociation [8]. Progress has also been made toward threedimensional MFPAD measurement using coincidence detection and velocity map imaging [9]. Here we present photoelectron imaging of methane molecules, where both the photoelectron momentum and corresponding body frame of the polyatomic molecule are fully determined in all three dimensions.For many molecules, including CH 4 , core ionization opens a strong simultaneous double Auger decay channel that produces a trication that then can disso...

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The role of the methyl ion in the fragmentation of CH₄²⁺

Cited by 29 publications

References 40 publications

Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

Probing dissociative molecular dications by mapping vibrational wave functions

Imaging Polyatomic Molecules in Three Dimensions Using Molecular Frame Photoelectron Angular Distributions

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The role of the methyl ion in the fragmentation of CH42+

Cited by 29 publications

References 40 publications

Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

Probing dissociative molecular dications by mapping vibrational wave functions

Imaging Polyatomic Molecules in Three Dimensions Using Molecular Frame Photoelectron Angular Distributions

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The role of the methyl ion in the fragmentation of CH₄²⁺