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  • Research into Process of Studying Photoionization Reveals Need for Change

    In order to understand fully the process of photoionization on a solid or a gas, counts of electrons being emitted from an atom are essential. In a perfect world, the best way to ensure an accurate count of rate changes would be to detect the number of electrons from every possible angle around an atom--an impossible task. Typically, a detector is placed in a static point around the atom, from which counts are made and a formula is used to make inferences about the behavior of electrons around the entirety of the atom. But the authors of a recent paper released in Physical Review Letters offer a new look into the formula usually used for this situation and offer evidence that it is inaccurate. The issue at hand is dealing with angular distribution, or the difference in electron distribution depending on what angle the detector is placed--an essential piece of the photoionization puzzle.

    "The new paper shows the right formula to use in order to correct for angular dependences, provided you know all the parameters. These parameters can be very different for different processes, so there is no general 'remedy' to this problem, but at least people have to be aware of it and know what needs to be measured," explains Ralf Wehlitz, SRC Associate Scientist and one of the authors of the PRL.

    O. Hemmers, R. Guillemin, D. Rolles, A. Wolska, D. W. Lindle, E. P. Kanter, B. Krässig, S. H. Southworth, R. Wehlitz, B. Zimmermann, V. McKoy, and P. W. Langhoff: Low-Energy Nondipole Effects in Molecular Nitrogen Valence-Shell Photoionization
    Phys. Rev. Lett. 97, 103006-1 - 103006-4 (2006)