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Dissociative double photoionisation of CO below the adiabatic double ionisation threshold has been studied by the time-of-flight photoelectron–photoelectron coincidence (TOF-PEPECO) and the velocity imaging photoionisation coincidence (VIPCO) methods. By combining the results from the two methods which give complementary information, the double photoionisation process is identified to CO + hv→ CO+* + e− → C+(2P) + [O+(2D/2P)]nl + e− → C+(2P) + O+(4S) + 2e−. The high energy resolution of the TOF-PEPECO spectrometer enables us to resolve individual fragment [O+(2D/2P)]nl states and also intermediate CO+* states. The angular correlations between electrons and ions, deduced from the VIPCO data, imply that the nuclear dissociation is faster or at least comparable in the time scale with molecular rotation, and that the second electron emission occurs after the C+ and O* atoms are far apart. A possible generic identification of the intermediate states is suggested. [Copyright &y& Elsevier]

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]

Using the velocity imaging photoionization coincidence technique we have determined molecular-frame photoelectron angular distributions for ionization of H2 to the 2pσu, 2sσg and 2pπu states of H2+ from angular correlation between photoelectrons and the product protons. The results are analyzed in terms of electric dipole transitions populating symmetry-allowed low-l partial waves. In perpendicular ionization to 2pσu an almost pure dπg wave is observed, in accordance with simple symmetry predictions. [Copyright &y& Elsevier]

A new apparatus has been developed to detect and measure angular correlations between energy-selected photoelectrons and coincident mass-analyzed fragment ions from photoionization at selected wavelengths. It achieves velocity imaging for electrons and ions simultaneously and has high collection efficiency for both particles, with moderate mass and energy resolution. Angular and energy correlations between the two particles are measured, as are the angular distributions of each particle independently relative to the light polarization direction. Fixed-molecule electron angular distributions are deduced in cases of pure axial recoil. Examples of angular distributions from photoionization of diatomic molecules are reported. © 2000 American Institute of Physics. [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]