2016). Photoionization microscopy for a hydrogen atom in parallel electric and magnetic fields. Physical Review A, 93(6), 063411. AbstractIn photoionization microscopy experiments, an atom is placed in static external fields, it is ionized by a laser, and the electron falls onto a position-sensitive detector. The current of electrons arriving at various points on the detector depends upon the initial state of the atom, upon the excited states to which the electron is resonantly or non-resonantly excited, and upon the various paths leading from the atom to the final point on the detector. We report here the first quantum-mechanical computations of photoionization microscopy in parallel electric and magnetic fields. We focus especially on the patterns resulting from resonant excited states. We show that the magnetic field substantially modifies some of these resonant states, confining them in the radial direction, and that it has a strong effect on the interference pattern at the detector.

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We study the core effect of nonhydrogenic alkaline-earth-metal barium in its diamagnetic spectrum by one photon transition from the ground state 6s 2 1 S 0 experimentally and theoretically. The non-Coulombic potential of the ion core introduces an extra energy shift compared with hydrogen and a level anticrossing between different n manifolds, characterized by the quantum defect of the concerned angular momentum states. With a complex rotation coordinate technique and a B-spline expansion method, we develop a matrix-form Hamiltonian based on an effective potential incorporating the angular-dependent quantum defect into the angular rotation term. The nonhydrogen core effects are investigated by sweeping the quantum defects of different channels in the calculation. Results show that quantum defects of p and f states have a undeniable effect on the intensities and positions of the spectral lines, although barium is closely hydrogenlike in the energy range examined. The anticrossing spectral lines are also identified with the aid of theoretical calculations. The calculations are in good agreement with the experimental observations.