Holographic detection of parity in atomic and molecular orbitals

We introduce a novel and concise methodology to detect the parity of atomic and molecular orbitals based on photoelectron holography, which is more general than the existing schemes. It fully accounts for the Coulomb distortions of electron trajectories, does not require sculpted fields to retrieve phase information and, in principle, is applicable to a broad range of electron momenta. By comparatively measuring the differential photoelectron spectra from strong-field ionization of N$_{2}$ molecules and their companion atoms of Ar, some photoelectron holography patterns are found to be dephased for both targets. This is well reproduced by the full-dimensional time-dependent Schr\"{o}dinger equation and the Coulomb quantum-orbit strong-field approximation (CQSFA) simulation. Using the CQSFA, we trace back our observations to different parities of the 3$p$ orbital of Ar and the highest-occupied molecular orbital of N$_{2}$ via interfering Coulomb-distorted quantum orbits carrying different initial phases. This method could in principle be used to extract bound-state phases from any holographic structure, with a wide range of potential applications in recollision physics and spectroscopy

Strongly Enhanced Backward Emission of Electrons in Transfer and Ionization

We studied three-dimensional angular distributions and longitudinal momentum spectra of electrons ejected in transfer plus ionization (TI), i.e., the ejection of one and the capture of a second target electron, for ion-helium collisions. We observe a pronounced structure strongly focused opposite to the projectile beam direction, which we associate with a new correlated TI mechanism proposed recently. This process contributes significantly to the total cross sections over a broad range of perturbations η, even at η as large as 0.5, where uncorrelated TI mechanisms were thought to be dominant

Sequential and Direct Two-Photon Double Ionization of D₂ at Flash

Sequential and direct two-photon double ionization (DI) of D2 molecule is studied experimentally and theoretically at a photon energy of 38.8 eV. Experimental and theoretical kinetic energy releases of D++D+fragments, consisting of the contributions of sequential DI via the D2+(1sσg) state and direct DI via a virtual state, agree well with each other

Fragmentation pathwaysfor selected electronic states of theacetylene dication

Coincident measurement of the Auger electron and fragmention momenta emitted after carbon core-level photoionization of acetylenehas yielded new understanding of how the dication fragments. Ab initiocalculations and experimental data, including body-frame Auger angulardistributions, are used to identify the parent electronic states andtogether yield a comprehensive map of the dissociation pathways whichinclude surface crossings and barriers to direct dissociation. The Augerangular distributions show evidence of core-holelocalization

Angular Scattering in Fast Ion-Atom Electron Transfer Collisions: Projectile Wave Diffraction and Thomas Mechanisms

We report experimental angular differential cross sections for double-electron capture in He2+ + He collisions and single-electron capture in H+ + He collisions for the 1.3-12.5 MeV kinetic energy range. In all cases, the total cross sections are dominated by forward scattering peaks in dσ/dΩ. The shapes and widths (but not the magnitudes) of these peaks are very similar for all energies and for capture of one or two electrons corresponding also to our measured linear increases in the transverse momentum transfers with increasing projectile velocities. These observations may be ascribed to diffraction limitations which are connected to electron transfer probabilities P(b) which are significant in limited regions of b only. For the H+ + He single-electron capture we observe two additional maxima in the angular differential cross sections. We conclude that while the secondary maxima at ~0.5 mrad probably have large contributions from the Thomas proton-electron-nucleus scattering mechanism, the third maxima at ~0.75 mrad are most likely mainly due to projectile de Broglie wave diffraction

Two-Center Double-Capture Interference in Fast H e²⁺+ H₂ Collisions

We report the first observation of Young-type interference effects in a two-electron transfer process. These effects change strongly as the projectile velocity changes in fast (1.2 and 2.0 MeV) He2++H2 collisions as manifested in strong variations of the double-electron capture rates with the H2 orientation. This is consistent with fully quantum mechanical calculations, which ignore sequential electron transfer, and a simple projectile de Broglie wave picture assuming that two-electron transfer probabilities are higher in collisions where the projectile passes close to either one of the H2 nuclei

Formation of inner-shell autoionizing CO+ states below the CO++ threshold

We report a kinematically complete experiment on the production of CO{sup +} autoionizing states following photoionization of carbon monoxide below its vertical double ionization threshold. Momentum imaging spectroscopy is used to measure the energies and body-frame angular distributions of both photo- and autoionization electrons, as well as the kinetic energy release (KER) of the atomic ions. This data, in combination with ab initio theoretical calculations, provides insight into the nature of the cation states produced and their subsequent dissociation into autoionizing atomic (O*) fragments