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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Photoionization microscopy in terms of local-frame-transformation theory

Two-photon ionization of an alkali-metal atom in the presence of a uniform electric field is investigated using a standardized form of the local-frame-transformation and generalized quantum defect theory. Here, the relevant long-range quantum defect parameters in the combined Coulombic plus Stark potential are calculated with eigenchannel R-matrix theory applied in the downstream parabolic coordinate η. The present formulation permits us to express the corresponding microscopy observables through the local frame transformation, and it gives a critical test of the accuracy of the Harmin-Fano theory.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Fully differential single-photon double photoionization of atomic magnesium

The valence-shell double ionization of atomic magnesium is calculated using a grid-based representation of the 3s 2 electron configuration in the presence of a fully occupied frozen-core configuration of the remaining ten electrons. Atomic orbitals are constructed from an underlying finite-element discrete variable representation that facilitates accurate representation of the interaction between the inner-shell electrons with those entering the continuum. Length and velocity gauge results are compared with recent theoretical calculations and experimental measurements for the total double-, single-, and triple-differential cross sections, particularly at the photon energy of 55.49 eV for the last one. Comparison between the similar processes of double ionization of the ns 2 atoms helium, beryllium, and magnesium further illuminates the role of valence-shell electron correlation in atomic targets with heliumlike electronic configurations and symmetry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Angle-resolved Wigner time delay in atomic photoionization: The 4 d subshell of free and confined Xe

The angular dependence of photoemission time delay for the inner nd 3/2 and nd 5/2 subshells of free and confined Xe is studied in the dipole relativistic random phase approximation. A finite spherical annular well potential is used to model the confinement due to fullerene C 60 cage. Near cancellations in a variety of the dipole amplitudes, Cooper-like minima, are found. Overall, the effects of confinement on the angular dependence, primarily confinement resonances, are demonstrated and detailed.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Near- K -edge single, double, and triple photoionization of C + ions

Single, double, and triple ionization of the C + ion by a single photon have been investigated in the energy range 286 to 326 eV around the K-shell single-ionization threshold at an unprecedented level of detail. At energy resolutions as low as 12 meV, corresponding to a resolving power of 24 000, natural linewidths of the most prominent resonances could be determined. From the measurement of absolute cross sections, oscillator strengths, Einstein coefficients, multielectron Auger decay rates, and other transition parameters of the main K-shell excitation and decay processes are derived. The cross sections are compared to results of previous theoretical calculations. Mixed levels of agreement are found despite the relatively simple atomic structure of the C + ion with only five electrons. Finally, this paper is a followup to a previous Letter [A. Müller, Phys. Rev. Lett. 114, 013002 (2015)PRLTAO0031-900710.1103/PhysRevLett.114.013002].

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Dynamical electron vortices in attosecond double photoionization of H 2

We study electron momentum vortices in single-photon double ionization of H 2 by time-delayed, counter-rotating, elliptically polarized attosecond pulses propagating along kˆ either parallel or perpendicular to the molecular axis R. For ˆk∥R, kinematical vortices occur similar to those found for He. For kˆ⊥R, we find dynamical vortex structures originating from an ellipticity-dependent interplay of 1 Σ$^{+}_{u}$ and 1 Π$^{+}_{u}$ continuum amplitudes. Furthermore, we propose a complete experiment to determine the magnitudes and relative phase of these amplitudes by varying pulse ellipticities and time delays.

74 ATOMIC AND MOLECULAR PHYSICS↗