Beyond the Dipole Approximation: Angular-Distribution Effects in the 1s Photoemission from Small Molecules
نویسندگان
چکیده
Over the past two decades, the dipole approximation has facilitated a basic understanding of the photoionization process in atoms and molecules. Recent experiments on the Is inner shells of small molecules at relatively low photon energies (< 1000 eV) show strong nondipole effects. They are significant and measurable at energies close to threshold, in conflict with a common assumption that the dipole approximation is valid for photon energies below 1 keV. INTRODUCTION The electric-dipole (El) approximation [1], applied to photoionization, leads to the well-known expression for the differential cross section [2],
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