Measurements of Absolute Cross Sections for (e,H2) Collision Processes. Formation and Decay ofH

Abstract

Energy and angular&dependences of the elastic and inelastic scattering of electrons from H2 have been measured in the energy range 10 to 16 eV and for scattering angles ranging from 10' to 120'. Three resonance series have been investigated starting at 11.30, ll. 50, and 13.63 eV, respectively. The last two series decay preferentially into one single electronic channel, while the first resonance (resonance I) decays into all energetically possible exit channels, i.e. , X'Z~, b Z'", B'Z'". Throughout, stress is laid on the importance of absolute cross sections and reported values, and excitation f unctions have been presented in absolute units. The cross sections for the elastic channel and some inelastic channels (X Z'", v = 1 and 2, and the dissociative continuum b Z'") are composed of resonant and nonresonant scattering and show pronounced and rapidly changing interference structures. Relative branching ratios for resonance series I in terms of absolute total cross sections have been listed for those channels where practically no direct scattering amplitude is present. Summarizing those results, one cgn state that the probabilities (branching ratios) for the decay of resonance series I into the three electronicstates X Z~, b Z'", and B Z'"of the H& molecule summed over all vibrational states of the exit channel are of the same order of magnitude.From the observed angular dependence of the scattered electrons, the configuration of the resonances has been determined and compared with existing theoretical predictions.

Symmetry breaking by quantum coherence in single electron attachment

“…However, very little information is available for the 14 eV process as compared to that for the 4 eV and 10 eV processes. Transmission as well as scattering experiments had indicated the presence of a 2 Σ g + NIR in the 11eV to 13.5 eV range [20,21]. The same NIR was identified in the electron scattering experiments at 14 eV with a width of 90 meV [21].…”

“…Transmission as well as scattering experiments had indicated the presence of a 2 Σ g + NIR in the 11eV to 13.5 eV range [20,21]. The same NIR was identified in the electron scattering experiments at 14 eV with a width of 90 meV [21]. Subsequent DA measurements concluded that this Σ g + NIR is the main contributor to the 14 eV DA process [22] and this has been the accepted wisdom until now [16,23].…”

Cross sections for electron-impact excitation of the H2molecule using the MOB-SCI strategy

“…Weingartshofer et al [6], Watson and Anderson [7], Srivastava and Jansen [8], Hall and Andric [9], Ajello et al [10], Nishimura and Danjo [11], Mason and Newell [12], Khakoo and Trajmar [13][14][15], Khakoo and Segura [16] and, more recently, by Wrkich et al [17].…”

Differential cross sections for near-threshold electron impact dissociation of molecular hydrogen

“…Prior to the Trajmar et al review there was only one study of absolute excitation cross sections for this state, by Weingartshofer et al (1970) and these values have been tabulated by They measured DCS at four energies, 10.5, 11.0, 11.6 and 12.0 eV and also derived integral cross sections at each of these energies. Unfortunately, they do not provide tabulated cross sections.…”