Valence-shell photoionization of Cℓ-like Ar⁺Ions

Abstract

Absolute cross-section measurements for valence-shell photoionization of Ar + ions are reported for photon energies ranging from 27.4 eV to 60.0 eV. The data, taken by merging beams of ions and synchrotron radiation at a photon energy resolution of 10 meV, indicate that the primary ion beam was a statistically weighted mixture of the 2 P o 3/2 ground state and the 2 P o 1/2 metastable state of Ar + . Photoionization of this C -like ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. Observed resonance lineshapes indicate interference between indirect and direct photoionization channels. Resonance features are spectroscopically assigned and their energies and quantum defects are tabulated. The measurements are satisfactorily reproduced by theoretical calculations based on an intermediate coupling semi-relativistic Breit-Pauli approximation.

Compact realization of all-attosecond pump-probe spectroscopy

“…On the basis of estimations and measurements in our experiment, we assume n = 10 13 cm −3 , N pump = 3.75 × 10 7 photons, and N probe = 2.8 × 10 7 photons. In addition, a cross section of 32.5 Mb is used for the ionization of Ar at 20 eV ( 33 ), and a cross section of 10 Mb is used for the ionization of Ar + at 33.5 eV ( 34 ). With these numbers, we predict the generation of 2 to 3 Ar 2+ ions per laser shot.…”