Interatomic Coulombic Decay following Photoionization of the Helium Dimer: Observation of Vibrational Structure

Using synchrotron radiation we simultaneously ionize and excite one helium atom of a helium dimer (He_2) in a shakeup process. The populated states of the dimer ion (i.e. He^[*+](n = 2; 3)-He) are found to deexcite via interatomic coulombic decay. This leads to the emission of a second electron from the neutral site and a subsequent coulomb explosion. In this letter we present a measurement of the momenta of fragments that are created during this reaction. The electron energy distribution and the kinetic energy release of the two He^+ ions show pronounced oscillations which we attribute to the structure of the vibrational wave function of the dimer ion.Comment: 8 pages, 5 figure

Single photon double ionization of the helium dimer

We show that a single photon can ionize the two helium atoms of the helium dimer in a distance up to 10 {\deg}A. The energy sharing among the electrons, the angular distributions of the ions and electrons as well as comparison with electron impact data for helium atoms suggest a knock-off type double ionization process. The Coulomb explosion imaging of He_2 provides a direct view of the nuclear wave function of this by far most extended and most diffuse of all naturally existing molecules.Comment: 10 pages, 5 figure

Interatomic Coulombic decay following the Auger decay: Experimental evidence in rare-gas dimers

Interatomic Coulombic decay (ICD) in Ar(2), ArKr and Kr(2) following Ar 2p or Kr 3d Auger decay has been investigated by means of momentum-resolved electron-ion-ion coincidence spectroscopy. This sequential decay leads to Coulombic dissociation into dication and monocation. Simultaneously determining the kinetic energy of the ICD electron and the kinetic energy release between the two atomic ions, we have been able to unambiguously identify the ICD channels. We find that, in general, spin-conserved ICD, in which the singlet (triplet) dicationic state produced via the atomic Auger decay preferentially decays to the singlet (triplet) state, transferring the energy to the other atom, is faster than spin-flip ICD, in which the Auger final singlet (triplet) dicationic state decays to the triplet (singlet) state. However, spin-flip ICD may take place when spin-conserved ICD becomes energetically forbidden. Dipole-forbidden ICDs from Kr(2+)(4s(-2) (1)S)-B (B = Ar or Kr) to Kr(2+)(4p(-2) (1)D, (3)P)-B(+) are also observed. (c) 2008 Elsevier B.V. All rights reserved

Single photon induced symmetry breaking of H2 dissociation

H{sub 2}, the smallest and most abundant molecule in the universe, has a perfectly symmetric ground state. What does it take to break this symmetry? Here we show that the inversion symmetry can be broken by absorption of a linearly polarized photon, which itself has inversion symmetry. In particular, the emission of a photoelectron with subsequent dissociation of the remaining H{sub 2}{sup +} fragment shows no symmetry with respect to the ionic H+ and neutral H atomic fragments. This result is the consequence of the entanglement between symmetric and antisymmetric H{sub 2}{sup +} states resulting from autoionization. The mechanisms behind this symmetry breaking are general for all molecules

Interference, decoherence and its dependence on the internuclear distance

8 páginas, 2 figuras.-- et al.We report on fully differential cross sections for double ionization of H2 by a single circularly polarized photon of 160 eV energy. For an unequal sharing of the energy between the two electrons and a particular geometry where the influence of electron/electron interaction is constant, we find a four-lobe structure in the molecular frame angular distribution of the faster electron. This structure is interpreted to be due to a coherent emission of the electron from the two atomic centers of the molecule. This Young-type interference pattern is lost for other geometries, where electron-electron interaction plays a major role. Furthermore, we show that the interference structure depends strongly on the internuclear distance.The work was supported by the Deutsche Forschungsgemeinschaft and by the Office of Basic Energy Sciences, Division of Chemical Sciences of the US DOE under contract DE-AC03-76SF00098.Peer reviewe

Probing molecular bond-length using molecular-frame photoelectron angular distributions

The molecular-frame photoelectron angular distributions (MFPADs) in O 1s photoemission from CO2 molecule were measured. Patterns dueto photoelectron diffractions were observed in the MFPADs. The polarization-averaged MFPADs were compared with theoretical calculationand were found to be useful in determining the molecular bond-length, which is a component to determine molecular structures

Evidence of interatomic Coulombic decay in ArKr after Ar 2p Auger decay

Abstract We have identified interatomic Coulombic decay (ICD) processes in the ArKr dimer following Ar 2p Auger decay, using momentum-resolved electron-ion-ion coincidence spectroscopy and simultaneously determining the kinetic energy of the ICD electron and the KER between Ar 2+ and Kr + . We find that the spin-conserved ICD processes in which Ar 2+ (3p −3 3d) 1 P and 3 P decay to Ar 2+ (3p −2 ) 1 D and 3 P, respectively, ionizing the Kr atom, are significantly stronger than the spin-flip ICD processes in which Ar 2+ (3p −3 3d) 1 P and 3 P decay to Ar 2+ (3p −2 ) 3 P and 1 D, respectively