Fully differential cross sections for photo-double-ionization of D2

We report the first kinematically complete study of the four-body fragmentation of the D2 molecule following absorption of a single photon. For equal energy sharing of the two electrons and a photon energy of 75.5 eV, we observed the relaxation of one of the selection rules valid for He photo-double-ionization and a strong dependence of the electron angular distribution on the orientation of the molecular axis. This effect is reproduced by a model in which a pair of photoionization amplitudes is introduced for the light polarization parallel and perpendicular to the molecular axis

High Resolution (e,2e) Measurements using a New Toroidal Spectrometer

A new electron coincidence spectrometer based around toroidal sector electrodes is described, whose design has been optimised for electron impact induced (e,2e) ionization studies. An improvement in data collection efficiency of more than three orders o

Dynamics of Ionization Processes Studied with the COLTRIMS Method - New Insight into e-e Correlation

Many particle dynamics in atomic and molecular physics has been investigated by using the COLTRIMS method. The method and its power is discussed. The COLTRIMS technique visualizes many-particle fragmentation processes in the eV and sub milli-eV regime and reveals like the bubble chamber the complete momentum pattern in atomic and molecular particles reactions. Complete differential cross sections in momentum space have been measured for the transfer ionization channel in fast four-body (p+He→H°+He2++e) collisions. The correlated kinematical transfer ionization channel has been used to probe the highly correlated contributions to the asymptotic parts (high momenta and large nuclear impact parameters) of the He ground-state momentum wave function. In this reaction, one electron with selected initial momentum (2.5-7.5a.u.) in the He ground state is kinematically captured by the proton (tunneling through the two-center barrier). The measured three-particle final-state momentum distributions show well-structured patterns, which reflect special features of the three-particle initial-state momentum wave function

Revealing the Non-s 2 Contributions in the Momentum Wave Function of Ground-state He

The correlated Tunneling Transfer Ionization (TuTI) channel in fast 4-body processes p + He → H0 + He2+ +e is utilized to probe the highly correlated asymptotic parts of the He ground-state momentum space wave function. In this reaction, predominantly

Complete Photo-Fragmentation of the Deuterium Molecule

All properties of molecules - from binding and excitation energies to their geometry - are determined by the highly correlated initial-state wavefunction of the electrons and nuclei. Details of these correlations can be revealed by studying the break-up of these systems into their constituents. The fragmentation might be initiated by the absorption of a single photon1-6, by collision with a charged particle7,8 or by exposure to a strong laser pulse9,10: if the interaction causing the excitation is sufficiently understood, the fragmentation process can then be used as a tool to investigate the bound initial state11,12. The interaction and resulting fragment motions therefore pose formidable challenges to quantum theory13,15. Here we report the coincident measurement of the momenta of both nuclei and both electrons from the single-plioton-induced fragmentation of the deuterium molecule. The results reveal that the correlated motion of the electrons is strongly dependent on the inter-nuclear separation in the molecular ground state at the instant of photon absorption

Many-particle Fragmentation Processes in Atomic and Molecular Physics - New Insight into the World of Correlation

Correlated many-particle dynamics in Coulombic systems, which is one of the unsolved fundamental problems in AMO-physics, can now be experimentally approached with so far unprecedented completeness and precision. The recent development of the COLTRIMS technique (COLd Target Recoil Ion Momentum Spectroscopy) provides a coincident multi-fragment imaging technique for eV and sub-eV fragment detection. In its completeness it is as powerful as the bubble chamber in high energy physics. In recent benchmark experiments quasi snapshots (duration as short as an attosecond) of the correlated dynamics between electrons and nuclei have been made for atomic and molecular objects. This new imaging technique has opened a powerful observation window into the hidden world of many-particle dynamics

Revealing the Effect of Angular Correlation in the Ground-state He Wavefunction: A Coincidence Study of the Transfer Ionization Process

A joint theoretical-experimental study of the transfer ionization process p + He → H0 + He2+ + e- is presented. For the first time all particles in the final state have been detected in triple coincidence. This fully differential measurement is in goo

Photo Double Ionization of Helium 100 eV and 450 eV above Threshold: II. Circularly Polarized Light

We present a joint experimental and theoretical study of the fully differential cross section of the photo double ionization of helium with left and right circularly polarized light at Eexc= 100 eV and 450 eV above the threshold. We analyse angular distributions for the slow electron and the normalized circular dichroism for various energy sharings of the excess energy between the two electrons. The experimental results are well reproduced by convergent close coupling calculations