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  • 1
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    Complex Correlation Kohn-T Method of Calculating Total and Elastic Cross Sections (2001)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: We report on the first part of a study of electron-hydrogen scattering, using a method which allows for the ab initio calculation of total and elastic cross sections at higher energies. In its general form the method uses complex 'radial' correlation functions, in a (Kohn) T-matrix formalism. The titled method, abbreviated Complex Correlation Kohn T (CCKT) method, is reviewed, in the context of electron-hydrogen scattering, including the derivation of the equation for the (complex) scattering function, and the extraction of the scattering information from the latter. The calculation reported here is restricted to S-waves in the elastic region, where the correlation functions can be taken, without loss of generality, to be real. Phase shifts are calculated using Hylleraas-type correlation functions with up to 95 terms. Results are rigorous lower bounds; they are in general agreement with those of Schwartz, but they are more accurate and outside his error bounds at a couple of energies,
    Keywords: Atomic and Molecular Physics
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  • 2
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    Mass Polarization Effect in He-like Ions: First and Second Order (2003)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: In a paper with a similar title Yamanaka has calculated the mass polarization effect (to first order in mu/M for several low-lying states of the two-electron atoms and ions with atomic number Z from 2 to 10. Here we improve the previous results by using Hylleraas variational wave functions with up to 560 terms and extend the calculation to include some additional states and the Z=1ground state. In addition, we compute the second-order effect using the method of pseudostate summation. In one appendix another method of computation is discussed and used as a check, while the energies of the Z=1 ions are presented and discussed in a second appendix.
    Keywords: Atomic and Molecular Physics
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  • 3
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    Complex Correlation Calculation of e(-) - H Total Cross Sections (2001)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Calculation of e(-) - H total and elastic partial wave cross sections is being carried out using the complex correlation variational T-matrix method. In this preliminary study, elastic partial wave phase shifts are calculated with the correlation functions which are confined to be real. In that case the method reduces to the conventional optical potential approach with 2 projection operators. The number of terms in the Hylleraas-type wave function for the S-1 phase shifts is 95 while for the S-3 it is 56, except for k = 0.8 where it is 84. Our results, which are rigorous lower bounds, are seen to be in general agreement with those of Schwartz, but they are of greater accuracy and outside of his error limits for k = 0.3 and 0.4 for S-1. The main aim of this approach is the application to higher energy scattering. By virtue of the complex correlation functions, the T-matrix is not unitary so that elastic and total scattering cross sections are independent of each other. Our results will be compared specifically with those of Bray and Stelbovics.
    Keywords: Atomic and Molecular Physics
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  • 4
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    Polarizabilities and Other Properties of the td Muons Molecular Ion (2001)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Wavefunctions of Hylleraas type were used earlier to calculate energy levels of muonic systems. Recently, we found in the case of the molecular ions H2+, D2+ and HD+ that it was necessary to include high powers of the internuclear distance in the Hylleraas functions to localize the nuclear motion when treating the ions as three-body systems without invoking the Born-Oppenheimer approximation. We try the same approach in a muonic system, td(mu-). Improved convergence is obtained for J = 0 and 1 states for shorter expansions when we use this type of generalized Hylleraas function, but as the expansion length increases the high powers are no longer useful. We obtain good energy values for the two lowest J = 0 and J = 1 states and compare them with the best earlier calculations. Expectation values are obtained for various operators, the Fermi contact parameters, and the permanent quadrupole moment. The cusp conditions are also calculated. The polarizability of the ground state is then calculated using second-order perturbation theory with intermediate J = 1 pseudostates. It should be possible to measure the polarizability by observing Rydberg states of atoms with td(mu-) acting as the nucleus.
    Keywords: Atomic and Molecular Physics
    Type: Atomic Physics; Apr 01, 2001; CT; United States
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  • 5
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    Electron-H P-Wave Elastic Scattering (2004)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: In previous papers [Bhatia and Temkin, Phys. Rev. A 64, 032709-1 (2001), Phys. Rev. A 66, 064702 (2002)], electron-hydrogen and electron-He(+) S-wave scattering phase shifts were calculated using the optical potential approach. This method is now extended to the singlet and triplet electron-H P-wave scattering in the elastic region. Phase shifts are calculated using Hylleraas-type correlation functions with up to 220 terms. Results are rigorous lower bounds to the exact phase shifts and they are compared to phase shifts obtained from previous calculations.
    Keywords: Atomic and Molecular Physics
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  • 6
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    Complex Correlation Calculation of e-H Total Cross Sections (2001)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Calculation of e-H total and elastic partial wave cross sections is being carried out using the complex correlation variational T-matrix method. In this preliminary study, elastic partial wave phase shifts are calculated with the correlation functions which are confined to be real. In that case the method reduces to the conventional optical potential approach with projection operators. The number of terms in the Hylleraas-type wave function for the S phase shifts is 95 while for the S it is 56, except for k=0.8 where it is 84. Our results, which are rigorous lower bounds, are given. They are seen to be in general agreement with those of Schwartz, but they are of 0 greater accuracy and outside of his error limits for k=0.3 and 0.4 for S. The main aim of this approach' is the application to higher energy scattering. By virtue of the complex correlation functions, the T matrix is not unitary so that elastic and total scattering cross sections are independent of each other. Our results will be compared specifically with those of Bray and Stelbovics.
    Keywords: Atomic and Molecular Physics
    Type: Jul 18, 2001 - Jul 24, 2001; NM; United States
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  • 7
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    Complex Correlation Calculation of e-H Total Cross Sections (2001)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: Calculation of e - H total and elastic partial wave cross sections is being carried out using the complex correlation variational T-matrix method. In this preliminary study, elastic partial wave phase shifts are calculated with the correlation functions which are confined to be real. In that case the method reduces to the conventional optical potential approach with projection operators.
    Keywords: Atomic and Molecular Physics
    Type: XXII ICPEAC; Jul 18, 2001 - Jul 24, 2001; Unknown
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  • 8
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    Photoejection with Excitation in H(-) and Other Systems (2015)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Lyman-alpha radiation, 1216 Angstroms , has been seen from the sun and from various astrophysical sources. This radiation arises from the radiative transition from the 2p(sup 2P) state to the 1s(sup 2S) state of the hydrogen atom. The 2P state can be excited from the 1s(sup 2S) state by electron impact. However, it is possible to produce this excited state by photodetachment of the H(-) ion, leaving the H atom in the 2P state. We have calculated cross sections for this process using Hylleraas-type functions for the H ion and using the exchange approximation for the photoelectron in the final continuum states of angular momenta equal to 0 and 2. The photoabsorption cross sections in Hions or He atoms leaving the hydrogen atom and helium ion in 2(sup 2S) are also calculated. Similar calculations havebeen carried out for the Li(+), Be2(+), and C4(+) ions.
    Keywords: Atomic and Molecular Physics
    Type: GSFC-E-DAA-TN32030 , Physical Review A; 91; 1; 012702
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  • 9
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    Atomic Data and Spectral Line Intensities for NI XVII (2011)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ni XVII. We include in the calculations the 23 lowest configurations, corresponding to 159 fine-structure levels: 3l3l', 3l4l0'' , and 3s5l0''' , with l,l' = s,p,d, l'' = s,p,d, f, and l''' = s,p,d. Collision strengths are calculated at five incident energies for all transitions at varying energies above the threshold of each transition. One additional energy, very close to the threshold of each transition, has also been included. Calculations have been carried out using the Flexible Atomic Code in the distorted wave approximation. Additional calculations have been performed with the University College London suite of codes for comparison. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates of the present work, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10(exp 8) - 10(exp 14) / cubic cm and at an electron temperature of logT(sub e)e(K) = 6.5, corresponding to the maximum abundance of Ni XVII. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database
    Keywords: Atomic and Molecular Physics
    Type: Atomic Data and Nuclear Data Tables; 97; 3; 189-224
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  • 10
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    Atomic Data and Spectral Line Intensities for Ni XI (2010)
    In:  Other Sources
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    Publication Date: 2019-07-19
    Description: Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ni XI. We include in the calculations the 10 lowest configurations, corresponding to 164 fine structure levels: 3s(sup 2)3p(sup 6), 3s(sup 2)3p(sup 5)3d, 3s(sup 2)3p(sup 4)3d(sup 2), 3s3p(sup 6)3d, 3s(sup 2)3p(sup 5)4l and 3s3p6 4l with l =.s, p, d. Collision strengths are calculated at five incident energies for all transitions: 7.1, 16.8, 30.2, 48.7 and 74.1 Ry above the threshold of each transition. An additional energy, very close to the transition threshold, has been added, whose value is between 0.06 Ry and 0.25 Ry depending on the lower level. Calculations have been carried out using the Flexible Atomic Code and the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates of the present work, combined with Close Coupling collision excitation rate coefficient available in the literature for the lowest 17 levels, statistical equilibrium equations for level populations are solved at electron densities covering the 10(exp 8)-10(exp 14) cu cm range and at an electron temperature of logT(sub c)(K)=6.1, corresponding to the maximum abundance of Ni XI. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.
    Keywords: Atomic and Molecular Physics
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