Die differentiellen Anregungsfunktionen dern+2-Zustände von Helium

Abstract

Energy and angular dependences for the electron impact excitation of the Helium 2 3S, 2 1S, 2 3p, and 2 1p states have been measured using monochromatic (0.05 eV) electrons in the energy range from 19 to 23 eV and for scattering angles ranging from 0 to 110 ~ The structures near the 2 3S-threshold have been analyzed in terms of resonant and non resonant i.e. direct scattering phase shifts. The first peak in this excitation function at 19.95 eV is mostly due to the rapid change with collision energy of the direct s-wave phase of the inelastic scattering, which in turn is a consequence of the existence of the 2 2S-resonance at 19.3 eV. The energy position and behaviour with collision energy of the first peak at 20.7 eV in the 2 1S-channel is in agreement with the predictions for the existence of a virtual resonance state of BURKE et al. A term sceme of the He-resonances with assignments of configurations is presented.Die Untersuchung yon Anregungsfunktionen in der N/ihe der Schwelle mit Hilfe monochromatischer Elektronen und durch den Nachweis der gestreuten Elektronen ist erst in den letzten Jahren technisch mSglich geworden. Dabei wurden neben der direkten Anregung A+e-~A*+e-Resonanzen, d.h. kurzlebige negative Ionenzust/inde

Theoretical investigation of the autoionization process in molecular collision complexes: Computational methods and applications to He*(23S)+H(12S)

“…In order to test our procedures, we have investigated the (1s2s 2 ) 2 S resonances of Li and He Ϫ , two three-electron atomic systems that closely resemble the collisional complex under consideration here: the He Ϫ resonance involves the same open shell 1s He orbital, and Li represents the united atom limit of He*(2s 3 S) ϩ H. Both cases have been treated previously by various theoretical methods [39][40][41][42][43][44][45] and comparison can be made with precise measurements of the resonance energies [46][47][48][49][50][51][52] and, in the case of He Ϫ , also with experimental data for the width. [46][47][48][49] As pointed out by Davis and Chung, 45 the proper account of electron correlation is essential for accurate results for the widths of these 2 S atomic resonances. A basis of 13s,7p,3d Gaussian functions, comparable to that used for He*ϩH, appeared to give converged results, once sufficiently diffuse functions had been included ͑to describe properly the continuum and the correlation in the resonance state͒.…”

High-resolution measurement of the helium1s2s2S2resonanc

“…(1), and Eq. (3) with & =2 for all higher terms. The lack of dependence on the formulation was checked by also using p~f rom Eq.…”

Electron impact differential and integral cross sections for excitation of the n = 2 states of helium at 29.2 eV, 39.2 eV and 48.2 eV

“…At present, while several measurements of integral cross sections for exciting the 2 1 P state have been reported [8]- [11], very few measurements of the differential cross sections for excitation of the n = 2 states below 60 eV have been made. Ehrhardt and coworkers [12]-[13] obtained relative differential cross sections near the threshold of these states which gave insight into the resonant processes which dominate these cross sections in this region. In pioneering work, Trajmar and coworkers [14]- [16] measured differential cross sections for these states between 26 eV and 55 eV up to a 700 scattering angle and placed them on an absolute scale by normalization to the optically measured 2 1P integral cross sections of Jobe and St. John [8].…”