Abstract
The excitation cross-sections of the nS states of atomic hydrogen, n = 2 to 6, by electron impact on the ground state of atomic hydrogen were calculated using the variational polarized-orbital method at various incident electron energies in the range 10 to 122 eV. Converged excitation cross-sections were obtained using sixteen partial waves (L = 0 to 15). Excitation cross-sections to 2S state, calculated earlier, were calculated at higher energies than before. Results obtained using the hybrid theory (variational polarized orbital method) are compared to those obtained using other approaches such as the Born–Oppenheimer, close-coupling, R-matrix, and complex-exterior scaling methods using only the spherical symmetric wave functions. Phase shifts and elastic cross-sections are given at various energies and angular momenta. Excitation rate coefficients were calculated at various electron temperatures, which are required for plasma diagnostics in solar and astrophysics to infer plasma parameters. Excitation cross-sections are compared with those obtained by positron impact excitation.
Highlights
Cecilia Payne, a student of Eddington, suggested that hydrogen is the most abundant element in the universe
The electron impact excitation of hydrogen to the 2p level resulting in Lyman-alpha radiation in astrophysics is well known
Temkin and Lamkin [14] showed that in the presence of the incident electron the target wave function can be written as φ0( r 2)
Summary
Cecilia Payne, a student of Eddington, suggested that hydrogen is the most abundant element in the universe. In earlier publications [2,3], cross-sections for excitation of the atomic hydrogen by electrons and positrons were presented. Burke et al [4], using the closecoupling approximation, carried out such a calculation Their wave function includes both 1S and 2S states for 2S excitation. Bartlett and Stelbovics [6] used the Temkin–Poet models to study electron-hydrogen scattering and calculated excitation cross-sections to various S states. Since the hydrogenic functions are exact, different approximations can be used to judge the possibility of obtaining accurate results. Even though the calculations were carried out as a single-channel approximation, the phase shifts obtained have lower bounds to the exact phase shifts and agree well with those obtained using other approximations.
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