Three-dimensional imaging of atomic four-body processes

Schulz, Michael; Moshammer, R.; Fischer, Daniel; Kollmus, H.; Madison, Don H.; Jones, S.; Ullrich, J.

doi:10.1038/nature01415

Cited by 273 publications

(323 citation statements)

References 18 publications

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“…This allows us to show how the electronic continuum momentum distribution depends on the inter-nuclear separation in the molecule and its orientation with respect to the photon polarization. [18,19,20,21]. In brief, inside our momentum spectrometer, a supersonic D 2 -gas jet was crossed with the linear polarized photon beam from the LBNL Advanced Light Source (D 2 provides a higher target density than a comparable H 2 gas jet and data less contaminated by random coincidences from background H 2 O).…”

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confidence: 99%

Complete photo-fragmentation of the deuterium molecule

Weber

Czasch

Jagutzki

et al. 2004

Nature

154

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However, despite 80 years of theoretical attention, near exact calculations for such systems are only available for bound states. On the experimental side, the tests of these calculations are largely based upon level energies or single particle momentum 3 distributions. Very promising and challenging new classes of experiments are those which achieve a complete description of the outcome following the excitation of the ground state to an unbound continuum. The momenta, i.e. the set of vectors, of all the fragments of an atom or molecule break-up can be measured in coincidence with high precision using state-of-the-art imaging and timing techniques [16]. These asymptotic many-particle momentum distributions are determined by the interaction inducing the fragmentation, the bound initial state from which it emerged, and the interactions between the outgoing particles. Thus it is useful to the experimentalist to keep the interaction process as simple as possible and to choose a geometry where final state interactions are negligible or under control. In the present study we used the absorption of a single photon to fragment the deuterium molecule: hν + D 2 → 2 e -+ 2 d + Due to their heavy masses, the initial motion of the nuclei in the continuum can be assumed the same as in the ground state at the instant of the electronic transition (Born Oppenheimer approximation). Once the electrons have left the system, the motion of the nuclei is solely determined by their Coulomb repulsion; they accelerate to a Kinetic Energy Release (KER) which corresponds to the Coulomb potential associated with their initial separation. Quantum mechanically one maps the nuclear vibrational wave-function onto the Coulomb potential to yield a KER spectrum. Inverting this process determines the squared nuclear vibrational wave-function from the measured KER spectrum [17]. Furthermore, by selecting events that occur within a fixed subregion in the KER spectrum, one samples molecules for which the corresponding internuclear distance is defined much more precisely than the full extent of the initial nuclear wave-function. This allows us to show how the electronic continuum momentum distribution depends on the inter-nuclear separation in the molecule and its orientation with respect to the photon polarization. [18,19,20,21]. In brief, inside our momentum spectrometer, a supersonic D 2 -gas jet was crossed with the linear polarized photon beam from the LBNL Advanced Light Source (D 2 provides a higher target density than a comparable H 2 gas jet and data less contaminated by random coincidences from background H 2 O). The electrons and ions created in the intersection of the photons with

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confidence: 99%

Complete photo-fragmentation of the deuterium molecule

Weber

Czasch

Jagutzki

et al. 2004

Nature

154

132

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“…This finding was particularly surprising given the fact that the measurements were carried out under kinematical conditions which are believed to be perfectly suitable for applicability of perturbative approaches: (i) |Z p |/v p = 0.1 a.u., where Z p and v p are the projectile charge and velocity, respectively, and (ii) small energy-and momentum-transfer values. Further discussions involved various attempts to explain the source of the discrepancies in the nodal structure, ranging from higher-order [4][5][6][7][8] and non-perturbative mechanisms [7,[9][10][11][12]] to experimental uncertainties [8,13] and so-called projectile coherence effects [14]. Though the explanation due to experimental uncertainties alone was refuted in [15], the very recent 1-MeV p+He experiment at momentum transfer of 0.75 a.u.…”

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Fully differential cross sections for singly ionizing 1-MeV p +He collisions at small momentum transfer: Beyond the first Born approximation

et al. 2017

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We present calculations of the electron angular distributions in the single ionization of helium by 1-MeV proton impact at momentum transfer of 0.75 a.u. and ejected-electron energy of 6.5 eV. The results using the first and second Born approximations and the 3C model with different trial helium functions are compared to the experimental data. A good agreement between theory and experiment is found in the case of the 3C final state and a strongly correlated helium wave function. The electron-electron correlations in the He atom are found to influence the ratio of the binary and recoil peak intensities.

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“…Collision systems involving atomic targets are potentially also significantly affected by the projectile coherence. For example, the longstanding puzzle regarding discrepancies between theory and experiment in the FDCS for ionization in 100 MeV/amu C 6+ + He collisions [2] could probably be solved by properly accounting for the localization of the projectile. More specifically, the incorrect assumption of a fully coherent projectile beam probably leads to artificial path interference between two (or more) different impact parameters, resulting in the same scattering angle, in theory [29].…”

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“…Here, we are particularly interested in the consequences of these properties of quantum-mechanics for scattering theory, which, in turn, directly deals with the fundamentally important and yet unsolved few-body problem (FBP) [2,3].…”

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confidence: 99%