Bernd Crasemann

Relativistic radiationless transition probabilities for atomic K- and L-shells☆

Abstract : Auger and Coster-Kronig transition probabilities have been calculated ab initio relativistically from perturbation theory, for frozen orbitals, in teh Dirac-Hartree-Slater approach. Results in the j-j coupling scheme are tabulated for or = 22 elements with atomic numbers 18 or = Z or = 96.

Theoretical L-shell Coster-Kronig energies 11 ≤ Z ≤ 103

Abstract Relativistic relaxed-orbital calculations of L -shell Coster-Kronig transition energies have been performed ab initio for all possible transitions in atoms with atomic numbers 11 ≤ Z ≤ 103. Hartree-Fock-Slater wavefunctions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first-order approximation to the local approximation was thus included. Quantum-electrodynamic corrections were made. Each transition energy was computed as the difference between results of separate self-consistent-field calculations for the initial, singly ionized state and the final two-hole state. The following quantities are listed: total transition energy, “electric” (Dirac-Hartree-Fock-Slater) contribution, magnetic and retardation contributions, and contributions due to vacuum polarization and self energy.

Relativistic cross sections for atomic K- and L-shell ionization by protons, calculated from a Dirac--Hartree--Slater model

Abstract Relativistic direct ionization cross sections for proton impact have been computed for atomic K and L shells, with Dirac-Hartree-Slater wave functions. Corrections for binding, polarization, and Coulomb deflection are included. Results are tabulated for proton energies from about 0.1 to 3 MeV, for 27 elements with atomic numbers 22 ⩽ Z ⩽ 92.

Auger and Coster-Kronig radial matrix elements for atomic numbers 6 ≤ Z ≤ 92

Abstract Coulomb radial matrix elements for Auger and Coster-Kronig transitions to K -, L 1 -, L 2 -, and L 3 -shell vacancies in singly ionized atoms have been calculated with relativistic Dirac-Hartree-Slater wave functions. Results are tabulated for atomic numbers Z = 6–87 for the K shell and Z = 12–92 for the L subshells. These matrix elements can be used to calculate approximate Auger rates in multiply ionized atoms; the matrix elements are expected to be very useful for the computation of Auger rates in molecules and can be applied in computations of valence-band Auger lineshapes in solids.

Decay of 75Se

Abstract The gamma-ray spectrum of 75Se has been studied with a high-resolution Ge(Li) spectrometer. Intensities (indicated in parentheses) of 12 lines and the energy of three lines above 401 keV have been measured: 66.05 keV (1.64±0.05), 96.74 keV (5.33±0.16), 121.12 keV (27.8±0.8), 135.99 keV (94.9±2.0), 198.60 keV (2.28±0.05), 264.62 keV (100), 279.57 keV (43.0±0.9), 304.0 keV (2.39±0.05), 400.7 keV (22.3±0.5), 419.6±0.5 keV [(3.22±0.06) × 10−2], 572.0±0.5 keV [(6.36±0.13) × 10−2] and 617.7±0.5 keV [(7.77±0.15) × 10−3]. Total K X-ray intensity and capture branching ratios have been determined; (5.8±1.8) % of all decays are found to lead to the ground state of 75As. The K-capture probability to the 401 keV level has been measured as PK/Ptotal = 0.885±0.018, in close agreement with the theoretical value of 0.88 computed after the theory of Brysk and Rose with allowance for electron exchange according to Bahcall.

Atomic K-, L-, and M-shell cross sections for ionization by protons: A relativistic hartree-slater calculation

Abstract Relativistic direct ionization cross sections for proton impact have been evaluated with Dirac-Hartree-Slater wave functions for atomic K , L , and M shells. Corrections for binding, polarization, and Coulomb deflection are included. Results are tabulated for proton energies from 3.25 to 5 MeV for the K shell and 1 to 5 MeV for the L subshells, for 28 elements with atomic numbers 22 ⩽ Z ⩽ 92. For M -subshell cross sections, results are tabulated for 15 elements with 54 ⩽ Z ⩽ 92, for proton energies from 0.06 to 2 MeV.

Theoretical atomic inner-shell energy levels, 70 ≤ Z ≤ 106

Abstract Theoretical 1s, 2s, 2p 1 2 , and 2p 3 2 energy levels in neutral atoms with 70 ≤ Z ≤ 106 are listed. The computations are relativistic and include complete relaxation. The electric energies are based on Dirac-Hartree-Slater wave functions; a first-order correction to the local approximation is made. The Breit-interaction energy and vacuum-polarization energy are listed separately, and a self-energy correction is included. These calculations differ from earlier work by the authors in that a more accurate, frequency-dependent expression for the Breit energy is employed, a Fermi (rather than uniform) distribution of the nuclear charge is assumed, and a screened self-energy correction is applied to the 1s, 2s, 2p 1 2 , and 2p 3 2 levels. Comparison of results with 1967 experimental values adopted by Bearden and new work of Borchert shows better agreement than is provided by earlier calculations with frequency-independent Breit interaction and a uniform nuclear charge distribution.

K-shell auger and radiative transitions in the boron isoelectronic sequence

Abstract Auger energies and rates and x-ray wavelengths and intensities for transitions to K -shell vacancies in boron-like ions with 1 s 2 s 2 2 p 2 , 1 s 2 s 2 p 3 , and 1 s 2 p 4 configurations have been calculated relativisically in terms of the multiconfiguration Dirac-Fock model. Seventeen ions with atomic numbers 6 ⩽ Z ⩽ 54 were considered. The Breit interaction and quantum-electrodynamic corrections were taken into account in the calculations. Transition rates were evaluated in intermediate coupling, including configuration interaction within the same complex. Line fluorescence yields were also computed.

Measurement of Nuclear Isomeric Half‐Lives in the Range from One Microsecond to Ten Milliseconds

Relatively simple and accurate delayed‐coincidence apparatus for the measurement of isomeric half‐lives in the millisecond range is described. Practical aspects of the statistics of delayed‐coincidence counting are discussed. Half‐life measurements of Ta181m (17.83±0.10 μsec) and Y88m (300.5±5.0 μsec) are described.

L x-ray satellite energies

Abstract Theoretical energies are tabulated for the L x-ray satellites that arise from electric dipole and quadrupole transitions in the presence of one spectator hole in the M- or N-shell. Results are listed for 11 elements with atomic numbers 65 ≤ Z ≤ 95. The computations are relativistic and include quantum-electrodynamic corrections. Subsidiary tables list the Coulomb and Breit interaction energies for double-hole states and the relative x-ray intensities of double-hole multiplet states.