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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Electron-He(+) P-wave Elastic Scattering and Photoabsorption in Two-electron Systems

In a previous paper [Bhatia, Phys. Rev. A 69,032714 (2004)], electron-hydrogen P-wave scattering phase shifts were calculated using the optical potential approach based on the Feshbach projection operator formalism. This method is now extended to the singlet and triplet electron-He(+) 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 the method of polarized orbitals and close-coupling calculations. The continuum functions calculated here are used to calculate photoabsorption cross sections. Photoionization cross sections of He and photodetachment cross sections of H(-) are calculated in the elastic region, i.e. leaving He(+) and H in their respective ground states, and compared with previous calculations. Radiative attachment rates are also calculated.

Bhatia, A. K.↗
NASA NTRS1974

Elastic and inelastic electron scattering at 20 and 60 eV from atomic Cu

Normalized differential and integral electron-impact cross sections are presented for elastic scattering and for specified excitation levels of atomic copper at 20 and 60 eV. For some excitation levels, an unexpectedly large cross section was found, which at certain angular and energy ranges surpasses the cross section for elastic scattering.

Williams, W.↗
NASA NTRS1991

Studies of electron collisions with polyatomic molecules using distributed-memory parallel computers

Elastic electron scattering cross sections from 5-30 eV are reported for the molecules C2H4, C2H6, C3H8, Si2H6, and GeH4, obtained using an implementation of the Schwinger multichannel method for distributed-memory parallel computer architectures. These results, obtained within the static-exchange approximation, are in generally good agreement with the available experimental data. These calculations demonstrate the potential of highly parallel computation in the study of collisions between low-energy electrons and polyatomic gases. The computational methodology discussed is also directly applicable to the calculation of elastic cross sections at higher levels of approximation (target polarization) and of electronic excitation cross sections.

Winstead, C.↗
NASA NTRS1987

Vibrationally elastic scattering cross section of water vapor by electron impact

Absolute differential cross sections of electrons vibrationally elastically scattered from water vapor have been measured at room temperature by electron impact. A modulated crossed-beam method was used. The energy and angular range covered were from 2.2 to 20 eV and from 15 to 150 deg, respectively. Strong backward scattering has been observed as predicted by theory. The measured integrated and momentum-transfer cross sections are generally larger than others in the literature by 50 percent.

Shyn, T. W.↗
NASA NTRS1967

Theory of atomic transitions

Transition probabilities of atomic collisions, elastic scattering of electrons, and excitation functions

ELECTRON COLLISION↗
NASA NTRS2014

D-Wave Electron-H, -He+, and -Li2+ Elastic Scattering and Photoabsorption in P States of Two-Electron Systems

In previous papers [A. K. Bhatia, Phys. Rev. A 85, 052708 (2012); 86, 032709 (2012); 87, 042705 (2013)] electron-H, -He+, and -Li2+ P-wave scattering phase shifts were calculated using the variational polarized orbital theory. This method is now extended to the singlet and triplet D-wave scattering in the elastic region. The long-range correlations are included in the Schrodinger equation by using the method of polarized orbitals variationally. Phase shifts are compared to those obtained by other methods. The present calculation provides results which are rigorous lower bonds to the exact phase shifts. Using the presently calculated D-wave and previously calculated S-wave continuum functions, photoionization of singlet and triplet P states of He and Li+ are also calculated, along with the radiative recombination rate coefficients at various electron temperatures.

D-wave↗
NASA NTRS2004

Electron-H P-Wave Elastic Scattering

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.

Bhatia, A. K.↗
NASA NTRS1993

Cross Sections for Electron Scattering by Ground State Ba; Elastic Scattering and Excitation of the ...6s6p (sup 1)P(sub 1) Level

Differential cross sections for elastic and inelastic (6s6p (sup 1)P(sub 1)) electron scattering from ground state Ba atom have been measured at 5eV, 10eV, 15eV, and 20eV impact energies in the angular range from 0(sup 0) to 130(sup 0). Extrapolation to the larger angles have been performed using theoretical calculations as a guide, and integral and momentum transfer cross sections were derived. Theoretical calculations based on two channel clos coupling and relativistic and non-relativistic distorted wave methods have been compared with the present results. Good agreement between experiment and various theoretical results is found at small scattering angles but significant deviations exist at larger scattering angles.

electon scattering extrapolation scattering angles↗
NASA NTRS2008

Applications of the Hybrid Theory to the Scattering of Electrons from HE+ and Li++ and Resonances in these Systems

Applications of the hybrid theory to the scattering of electrons from Ile+ and Li++ and resonances in these systems, A. K. Bhatia, NASA/Goddard Space Flight Center- The Hybrid theory of electron-hydrogen elastic scattering [I] is applied to the S-wave scattering of electrons from He+ and Li++. In this method, both short-range and long-range correlations are included in the Schrodinger equation at the same time. Phase shifts obtained in this calculation have rigorous lower bounds to the exact phase shifts and they are compared with those obtained using the Feshbach projection operator formalism [2], the close-coupling approach [3], and Harris-Nesbet method [4]. The agreement among all the calculations is very good. These systems have doubly-excited or Feshbach resonances embedded in the continuum. The resonance parameters for the lowest ' S resonances in He and Li+ are calculated and they are compared with the results obtained using the Feshbach projection operator formalism [5,6]. It is concluded that accurate resonance parameters can be obtained by the present method, which has the advantage of including corrections due to neighboring resonances and the continuum in which these resonances are embedded.

Bhatia, Anand K.↗
NASA NTRS1992

Probing hot-carrier transport and elastic scattering using ballistic-electron-emission microscopy

Ballistic-electron-emission microscopy (BEEM) has been used to characterize electron transport and scattering in metal/semiconductor structures. A SiO2 layer at the Au/Si interface was patterned to form transmitting and nontransmitting regions. By analyzing the BEEM current profiles at the boundaries of these regions, information on the spatial distribution of electrons after transport through the Au layer can be derived. A detailed comparison is made between the results presented here and models which involve modification of the electron distribution by scattering.

Milliken, A. M.↗