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Photoionization into the dissociation continuum of H2+(X2Σg+) has been studied using the velocity imaging photoionization coincidence method. Asymmetry parameters for the angular distributions of photoelectrons and fragment H+ ions have been measured at photon energies of 21.2, 23.1, 26.9 and 40.8 eV. Molecular frame photoelectron angular distributions (MF-PADs) have also been extracted for the parallel and perpendicular transitions at all the photon energies. All the MF-PADs show p-wave shape, which suggests a dominant p-wave contribution in the photoionization cross-sections at all energies. [Copyright &y& Elsevier]

Abstract: Simultaneous two-electron emissions from core-valence double photoionization in Ne and upon core-electron excitation in Ar have been studied using a very efficient multi-electron coincidence method. The former case demonstrates that the population ratio of singlet and triplet doubly-charged ion states reveals the double photoionization dynamics. The latter case shows that a weakly-bound electron can be used as a probe of the double Auger dynamics of a core-hole. In both cases, the inadequacy of the shake-off model is revealed by the experimental observations alone and the necessity to describe better electron correlation for two-electron emission, as done in the knock-out model. [ABSTRACT FROM AUTHOR]

Abstract: All the different Auger decay paths of Argon 2p holes have been characterized using a time of flight spectrometer of the magnetic bottle type. All electrons (the photoelectron and up to three Auger electrons) are detected in coincidence and resolved in energy. Double Auger decay is shown to proceed either through a direct process or by intense cascade paths, implying highly excited autoionizing Ar2+ states, which are identified as Ar2+ 3s−2 correlation satellites. Triple Auger decay is also observed and estimated to account for 0.2% only of all Auger decay. [Copyright &y& Elsevier]

Abstract: Auger electron spectroscopy (AES) and photoelectron spectroscopy (PES) are (with X-ray emission spectroscopy, XES) powerful analytical tools for material science and gas phase studies. However, the interpretation of Auger spectra can be very difficult due to the number and complexity of the involved processes. A deeper analysis, that allows a better understanding of relaxation processes following inner shell ionization, is possible with coincidence Auger spectroscopy. This method gives a new insight into electron correlation and allows disentangling of complex Auger electron spectra. In this paper, we present some examples related to gas phase coincidence Auger electron spectroscopy using synchrotron radiation. The detection in coincidence of an Auger electron with a threshold photoelectron presents two main advantages which are good energy resolution and high coincidence count rates. This technique has also provided new results on double Auger decay processes. A further qualitative breakthrough has been made with the development of a new experimental set-up based on a magnetic bottle time-of-flight electron spectrometer. This opens up the field of multi-electron coincidence spectroscopy and allows a most detailed analysis with characterization of all possible decay pathways following inner shell ionization. [Copyright &y& Elsevier]

Abstract: Double photoionisation spectra of ethyne and ethyne-d2 have been measured by the TOF–PEPECO technique and by the TPEsCO method with vibrational resolution. With the help of new calculations of the dication structure and Franck–Condon factors we deduce adiabatic double ionisation energies for the first three states of the normal hydrogen isotopomer as 31.74eV (X3Σg-), 32.42 (a1Δg) and 33.07 (b1Σg+). The two techniques give spectra with very different vibrational structure and reasons for the difference are discussed. [Copyright &y& Elsevier]

Abstract: An apparatus for electron–electron-fragment ion triple coincidence experiments has been developed to examine binary (e,2e) scattering reaction in the molecular frame. In the axial recoil limit of fragmentation of the residual ion, measurements of vector correlations among the three charged particles are equivalent to (e,2e) experiments with fixed-in-space molecules. Details and performance of the apparatus are reported, together with preliminary result of collision dynamics study on ionisation–excitation processes of fixed-in-space H2 molecules. We believe that this is the first observation of molecular frame (e,2e) cross sections. [Copyright &y& Elsevier]

The use of photoelectron angular distributions to determine the linear polarization of VUV light over a wide range of photon energies is demonstrated. Light at wavelengths from 256 to 736 A˚, partially polarized by large angle reflections in a toroidal grating monochromator and at a refocus mirror, has been analyzed. The results are validated by comparison measurements at spot wavelengths using multilayer polarizers. [Copyright &y& Elsevier]