Angular distribution of photoelectrons in resonant photoionization of polarized atoms (original) (raw)
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Theoretical study of inner-shell photoionization cross sections and angular distributions
Journal of the American Chemical Society, 1974
Atomic photoionization cross sections and asymmetry parameters are calculated using a simple oneelectron model potential consisting of the positive nuclear charge at the origin surrounded by a series of negatively charged spherical shells. The radial Schrodinger equation is solved exactly for unbound states of the potential using Whittaker functions. Parameters for the model potential (shell radii and charges) are fitted using SCF charge densities. Applications are made to inner-shell ionizations of atoms and molecules as observed in ESCA (Mg K a and A1 K a photon energies), with emphasis on 1s ionizations for boron through neon and 2s and 2p ionizations for aluminum through argon. The periodic variation in cross section for ionization of a given orbital is discussed in terms of the photoelectron kinetic energy. Effects due to core relaxation are considered for the neon atom. The calculations are compared with experimental X-ray absorption coefficients and photoelectron spectral intensities. hotoelectron spectroscopy using soft X-ray sources P has recently become a widely used experimental technique for studying atoms, molecules, and solids. The basic experiment consists of bombarding a sample to be studied with nearly monoenergetic photons and measuring the properties of the ejected photoelectrons. Although most of the emphasis has centered around the energetics of the photoionization process leading to a determination of electron binding energies, with recent advances in the experimental technique it has become feasible to determine the intensity3 of photoelectron peaks as well as the angular (spatial) distri-bution4l5 of the ejected photoelectrons. With these additional parameters the experimentalist can begin to unravel more complex photoelectron spectra.6 The in-(I) (a) K.
Physical Review Letters, 2004
Completely fine-structure-resolved photoelectron spectra produced from sodium atoms selectively excited into the Na 2p 6 3p 2 P 1=2 and 2 P 3=2 states were obtained using a third generation synchrotron source in conjunction with laser pumping and high-resolution spectrometry. The spectra show dramatically different behaviors. The strong variations observed in the regions of the Na 2p 5 3p 1;3 L J photolines and the Na 2p 5 4p 1;3 L J shakeup satellites are explained within a generalized geometrical model, accounting for the intermediate angular momentum coupling in the ionic states.
New Results in Photoionization of Laser-Excited Atoms
2003
The use of high-spectral resolution VUV-photon beams in atomic photoionization experiments has significantly increased over the past few years, owing to the number of operating third generation synchrotron radiation sources and associated high-resolution beam lines. For laser-excited atoms, however, the number of experiments is still low, because of the difficulties in combining the use of these two widely-different photon sources.
Physical Review Letters, 2005
Resonant atomic excitation by synchrotron radiation and subsequent ionization by a tunable dye laser is used to study the photoionization of short-lived Rydberg states in Xe. By combining circular and linear polarization of the synchrotron as well as of the laser photons the partial photoionization cross sections were separated in the region of overlapping autoionizing resonances of different symmetry and the parameters of the resonances were extracted.
Photoelectron angular distributions of excited atoms in intense laser fields
Physical Review A, 2014
Angular distributions of photoionization differential rates for an atom in arbitrary excited states ionized by intense laser fields with arbitrary polarization are reported. Relativistic effects are incorporated into the Keldysh theory, yielding semi-analytical expressions of ionization rates for hydrogenic initial states in intense linear, circular, and elliptical laser polarizations. Angular distributions are compared for different angular momentum quantum numbers, magnetic quantum numbers, and Keldysh parameters γ. The angular distributions are shown to depend strongly on γ , thus also reflecting the influence of relativistic effects. The sign of the magnetic quantum number, corresponding to different electron rotations, is shown to have a significant effect on photoelectron angular distributions in circularly polarized laser fields.
Angular Distributions of Photoelectrons and Partial Photoionization Cross-Sections
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1970
An experimental arrangement is given for measuring the angular distribution of photoelectrons. The asymmetry coefficient B is found to be 0.3 for Ar, and 0.3 and 0.12 for N2 at 584 A when the residual ion core is left in its X2z and A2II states, respectively. The partial photoionization cross-sections are given for O2 at 186, 209, 247, 330, and 460 A. New ionization potentials for O2 are found at 23.5, 24.6 and 27.3 eV ± 0.3 eV. The effects of autoionizing transitions on the population of vibrational states of N+2 are illustrated.
Photoelectron spectra in an autoionization system interacting with a neighboring atom
Physical Review A - PHYS REV A, 2011
Photoelectron ionization spectra of an autoionization system with one discrete level interacting with a neighbor two-level atom are discussed. The formula for long-time ionization spectra is derived. According to this formula, the spectra can be composed of up to eight peaks. Moreover, the Fano-like zeros for weak optical pumping have been identified in these spectra. The conditional ionization spectra depending on the state of the neighbor atom exhibit oscillations at the Rabi frequency. Dynamical spectral zeros occurring once per the Rabi period have been revealed in these spectra.
Physical Review Letters, 2000
We have measured the angle-resolved energy dependence of the electrons emitted over the energy range of the triply excited 2s 2 2p 2 P lithium resonance using synchrotron radiation. We have also calculated the behavior of the angular distribution parameter b using the R-matrix approximation. Experimental and theoretical results are in good agreement and show deep minima in the 1s2p 1, 3 P ionic channels. The energy at which the minima occur does not coincide with the resonance energy, but is shifted towards higher energy. PACS numbers: 32.80.Hd, 32.80.Fb In this Letter, we present the results of a new experiment investigating the angular distribution of electrons emitted in autoionization of the lowest-energy triply excited state of atomic lithium. We made a critical comparison of the data with the results of advanced Rmatrix calculations performed in order to interpret the energy behavior of the angular distribution parameter b. Photons from the Advanced Light Source (ALS) photoexcited the 2s 2 2p 2 P hollow lithium state both on and off resonance. The electrons emitted were angularly analyzed with a cylindrical mirror analyzer (CMA) electron spectrometer. The experimental results reveal a pronounced energy dependence of the angular distribution parameter b in the Li 1 1s2p 1, 3 P´l satellite channels, in good agreement with theoretical prediction. Both experiment and theory show that the minima in the b profiles occur on the high energy side of the resonance.