Gigantic enhancement of atomic nondipole effects: The 3s 3d resonance in Ca

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Dramatic examples of the importance of nondipole effects in photoelectron angular distributions at photon energies as low as a few tens of eV are found. This occurs in 3p photoionization of the Ca(42) atom and its ions Ca+(41) and Ca2+(40) at photon energies corresponding to a quadrupole 3s 3d resonance. The nondipole parameters are found to drastically increase to as much as 65% of the dipole counterpart. The quintessence is that this resonance turns out to be giant because of selective orbital collapse for the quadrupally excited 3d orbital. In addition, nondipole effects are known to result in an electric current the drag current in a gaseous medium upon photoionization of its atoms. We present our calculated data for the drag current in Ca vapor as well, in an attempt to trigger experimental studies of this interesting phenomenon in general. Calculations were performed within the framework of the random-phase approximation with exchange. © 2005 The American Physical Society.

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Physical Review A - Atomic, Molecular, and Optical Physics

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