Atomic-size Fraunhofer-type Diffraction for Single Electron Capture in He2+ + He Collision
Using the reaction microscope, the Angular Distributions of the Projectile (ADP) He+ in He2++He (1s2)→He+ (1s) + He+ (1s)reactions were obtained at incident electron energies of 40keV and 70keV at Institute of Modern Physics, Chinese Academy of Sciences (IMP). Clear oscillation structures in the ADP are observed (see fig.1).By analogy with the Fraunhofer Diffraction of light, the oscillations can be explained by the diffraction of incident ions on target atoms.
On the basis of a molecular Coulombic over-barrier model and a two-state model, the radius of the circular aperture has been calculated, with which the angular spacing and fringe position of the diffraction pattern are predicted. By comparing with the measured values, it is found that the two-state model (see fig.2) could well estimate the radius of the circular aperture, i.e. the range of impact parameters in which electron is captured with a great probability and the relative error is only 0.88% for incident energies of 40keV.Further, the radius of the circular aperture is nearly independent onincident energy in the energy range from 40 keV to 70 keV.
The results have been published in Journal of Physics B: At. Mol. Opt. Phys. 45 025202(2012)
Fig.1 Angularintensity distribution of the diffraction pattern for
He2++He (1s2) →He+ (1s) +He+ (1s). (Image by IMP)
Fig.2 Schematic diagramsfor two-state collision process. (Image by IMP)