A comparison of DWBA and coupled channels in the 2s-1d shell
Comparing coupled channels and distorted wave Born approximation optical model parameters in 2s-1d shell to investigate inelastic nucleon scattering
Ascuitto, R. J.↗
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Glauber theory of atomic hydrogen excitation by electron impact
Glauber and Born approximations of electron impact excitations of hydrogen atomic energy levels
Bassel, R. H.↗
Simultaneous ionization and charge transfer in fast-proton-helium-atom collisions
Cross sections for simultaneous ionization and charge transfer in fast proton-helium atom collisions, using Born approximation
Oldham, W. J. B., Jr.↗
Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91
The structures of Zr-93 and Zr-91 were studied by the stripping reaction Zr-92(d,p)Zr-93 and the pick-up reaction Zr-92(d,t)Zr-91 using 13 MeV incident deuterons. The reaction product particles were detected by counter telescope. Typical spectra from the reactions were analyzed by a nonlinear least squares peak fitting program which included a background search. Spin and parity assignments to observed excited levels were made by comparing experimental angular distributions with distorted wave Born approximation calculations.
Baron, N.↗
Excitation of Mg/+/ by electron collisions.
Demonstration that the Mg II resonance doublet at 2800 A represents a suitable diagnostic tool for the study of physical conditions in the solar chromosphere. The interpretation of intensities and line profiles requires the knowledge of all electron collision cross sections, which can affect directly or indirectly the population of upper levels of the doublet. For this purpose collision cross sections for transitions between levels 3s, 4s, 5s, 6s, 3p, 4p, 5p, 3d, 4d, and 5d have been calculated in the unitarized Coulomb-Born approximation without exchange. For the 3s-3p and 3s-3d transitions the present results are in a good agreement with the close-coupling calculations of Burke and Moores (1968).
Blaha, M.↗
Energy loss of a relativistic ion in a plasma.
The stopping power of a plasma for a relativistic heavy ion is calculated in a simplified derivation. The total contribution results from (1) individual electron scattering in the Coulomb field of the ion wherein large momentum transfers are involved and (2) small momentum transfers in which quantized plasma oscillations are excited. The resulting general formula for the stopping power is in agreement with a specialization of the results of a more elaborate treatment by Tsytovich. The nonrelativistic limit of the general formula agrees with an expression given earlier by Larkin from field-theory techniques and by the author in a Born-approximation approach. However, the general formula differs slightly in its details from that given by Hayakawa and Kitao.
Gould, R. J.↗
Collisional-rate coefficients for sodiumlike Ar VIII ions.
Determination of collisional-excitation-rate coefficients for sodium-like Ar VIII ions theoretically using the Coulomb-Born approximation as well as experimentally from the absolute intensities of lines emitted by these ions in well-diagnosed plasmas whose parameters were obtained from the analysis of scattered laser light. These plasmas were produced in a theta-pinch device. The agreement between theory and experiment is within the estimated accuracy of plus or minus 50% for excitation from the ground state to the n = 3 and n = 4 levels, whereas some deviations are observed for two transitions to the n = 5 levels at lower temperatures. A rate coefficient for ionization was obtained from the time dependence of the ionization.
Datla, R. U.↗
Energy loss of fast electrons and positrons in a plasma.
Calculation of the stopping power of a plasma for fast electrons and positrons. First the classical limit is considered where beta = v/c is much less than alpha is the fine structure constant. Then the nonrelativistic Born-approximation formulas are derived; this domain corresponds to alpha much less than beta much less than 1. Finally, the general case of relativistic electrons and positrons is treated; in the relativistic case the scattering cross sections of Moller (electron-electron) and Bhabha (positron-electron) are used in the calculation. In all three energy domains the problem is broken up into cases of small and large momentum transfers. For large q, scattering off individual plasma electrons is considered, while in the limit of very small q for the quantum-mechanical domain, excitation of quantized plasma oscillations contributes to dE/dx; in the classical limit for small q the polarizability of the plasma provides the effective cutoff. The formulas for the stopping power differ slightly from those for a heavy ion going through a plasma because there are exchange effects and the fast electrons and positrons can lose a large fraction of their energy in one scattering off a plasma electron.
Gould, R. J.↗
Electron impact excitation cross sections and energy degradation in CO.
We determine a comprehensive set of electron impact cross sections for carbon monoxide mainly on the basis of recently accumulated data on electron impact spectra, the Born approximation at high energies, and simple rules developed earlier to take into account low-energy effects. The calculation of the complete energy degradation of electrons incident on CO is carried out with these input cross sections, and the efficiencies associated with possible loss channels are presented.
Sawada, T.↗
A measurement of the relative cross sections for simultaneous ionization and excitation of the degenerate He(plus) n equals 4 levels
The relative cross sections for simultaneous ionization and excitation of helium by 200 eV electrons into the 4S, 4P, 4D and 4F levels have been measured via a fast delayed coincidence technique. Results are in poor agreement with Born approximation calculations for simultaneous ionization and excitation of helium, the 4P component being larger than expected.
Sutton, J. F.↗
Asymptotic form for the cross section for the Coulomb interacting rearrangement collisions
It is shown that in a rearrangement collision leading to the formation of the highly excited hydrogenlike states the cross section in all orders of the Born approximation behaves as 1/n sq, with n the principal quantum number, thus invalidating the Brinkman-Kramers approximation for large n. Similarly, in high energy inelastic electron-hydrogenlike atom collisions the exchange cross section for sufficiently large n dominates the direct excitation cross section.
Omidvar, K.↗
Calculation of electron energy flux distributions in noble gases.
The electron flux spectrum has been calculated over the entire range from delta-ray energies to ionization-potential energies. Estimates based on the Born approximation indicate that electron-gas atom elastic losses can be neglected. Gryzinski's (1965) classical cross sections show that electron-thermalized electron interactions can be ignored. Under those conditions the energy degradation is primarily due to the excitation and ionization of background gas.
Lo, R.↗
Calculation of energy loss by highly charged particles and the interpretation of cosmic ray data
The use of the Born approximation in describing the energy loss process for relativistic cosmic rays with Z above 20 underestimates the energy loss due to the production of high-energy secondary electrons. The implications of this fact for the response of various detectors, such as ion chambers, scintillators, emulsions, and Cerenkov counters are discussed.
Eby, P.↗
Acoustic scattering from a turbulent vortex
With the aid of the Born approximation, the time autocorrelation and power spectral density are calculated for the received acoustic signal scattered from velocity fluctuations in a turbulent aircraft trailing vortex. The turbulence is required to be globally stationary, but only locally homogeneous. The treatment includes the effects of spectral broadening due to convection of the scattering eddies by a spatially varying mean flow and by macroeddies. The 3 db bandwidth of the received signal is related to the scattering angle and the core Mach number of the vortex. A primary feature of the analysis is that it provides a method for inferring the radial intensity distribution of turbulence in a vortex. The analysis technique is also applicable to scattering from other turbulent flows where significant variations of turbulence level occur over distances on the order of the macroeddy size.
Ramsey, V. W.↗
Asymptotic form of the charge-exchange cross section in three-body rearrangement collisions
A three-body general-type rearrangement collision is considered in which the initial and final bound states are described by hydrogen-like wave functions. It is shown that the charge-exchange amplitude in the first Born approximation can be expanded at all incident energies in terms of the inverse powers of the principal quantum number (n). By expanding the exchange amplitude in this way, it is demonstrated conclusively that the cross section for capture into the s, p, and d states as well as for the sum over all the angular-momentum states is proportional to 1/n-cubed plus terms proportional to higher inverse odd powers of n. It is found that the low-lying levels cannot be scaled to the 1/n-cubed law irrespective of the value of the incident energy except in the case of capture into the s states in accordance with the Oppenheimer-Brinkman-Kramers approximation. Zeros and minima in the differential cross sections are given in the limit of high principal quantum number for electron capture by protons from atomic hydrogen and for positronium formation by proton-atomic hydrogen collisions.
Omidvar, K.↗
Investigation of forbidden transitions in argon ions
An attempt has been made to observe the visible forbidden argon coronal lines at 553.6 nm (Ar X), 691.7 nm (Ar XI), 847.6 nm (Ar XIII), and 441.2 nm (Ar XIV) in a deuterium-argon plasma produced in a large theta pinch. The electron temperature (250 eV) and the electron density (5 by 10 to the 16th power per cu cm) were measured by Thomson scattering of ruby laser radiation. This temperature is adequate to produce ionization stages up to Ar XIV, as was verified by photographic observation of Ar XIV lines. No line corresponding to the coronal lines was observed from the high-temperature plasma, but lines with wavelengths very nearly identical to those of two of the forbidden transitions were observed; these lines were due to allowed transitions of Ar II in a cooler portion of the plasma. Calculation of rate coefficients in the Coulomb-Born approximation shows that for laboratory experiments, electron collisions are much more important than radiative decay in depopulating the upper state of the forbidden lines.
Jalufka, N. W.↗
Satellite observations of snow and ice with an imaging passive microwave spectrometer
The scanning microwave spectrometer (SCAMS) on the Nimbus-6 satellite continuously maps the terrestrial surface with a resolution of about 150 km at 22.235 and 31.400 GHz. SCAMS observes at six angles besides nadir, yielding brightness temperatures which are a function of the distribution and character of various types of snow and ice, including microstructure and subsurface profiles in refractive index, loss (moisture or salinity), and temperature. Spectral signatures exhibiting interesting topographical structure have been observed. To aid in the interpretation of these data, a model was developed to describe the propagation of microwave intensity in a scattering medium characterized by three-dimensional random fluctuations of refractive index in addition to nonrandom variations in permittivity, temperature, and loss. The model combines Maxwell's equations in the Born approximation with radiative-transfer theory; this approach yields the variation of intensity with polarization, direction, and position.
Fisher, A. D.↗
Emissivity of half-space random media
Scattering of electromagnetic waves by a half-space random medium with three-dimensional correlation functions is studied with the Born approximation. The emissivity is calculated from a simple integral and is illustrated for various cases. The results are valid over a wavelength range smaller or larger than the correlation lengths.
Tsang, L.↗