We measured the Q-value and the scattering angle distributions for non-dissociative state selective single electron capture in collisions of 7.5 keV H+ and 15 keV H2+ with He. The experimental data are compared with semiclassical close-coupling calculations and predictions from the classical trajectory Monte Carlo simulations. By analogy with Fraunhofer diffraction, we also developed a toy model to reconstruct an imaginary screen that reflects the reaction impact-parameter dependence, in channels where the magnetic quantum number remains unchanged. It is well established that H2+ acts as a molecular double-slit in scattering processes. By demodulating the Young's double-slit-type interference pattern, we extracted the individual slit diffraction pattern of H2+ and compared it with that of the H+ atomic single-slit. For ground state electron capture, we found that the single and the double slit diffraction patterns have equal fringe width, whereas for excited state electron capture, diffraction patterns are quite different.
The authors report detailed experiments and comparison with first-principle theoretical calculation of the diffraction of cold neutrons ($\ensuremath{\lambda}\ensuremath{\approx}2$ nm) at single- and double-slit assemblies of dimensions in the 20-100 \ensuremath{\mu}m range. Their experimental results show all predicted features of the diffraction patterns in great detail. Particularly, their double-slit diffraction experiment is its most precise realization hitherto for matter waves.
We experimentally show novel phenomena: (1) in the same double slit or cross double slit experiment, within macroscopic distances from diaphragm, the patterns are non-interference and gradually evolve to the interference patterns near the screen; (2) in the same single slit or cross single slit experiment, within macroscopic distances from diaphragm, the patterns are non-diffraction and gradually evolve to the diffraction patterns near the screen; (3) in the same non-parallel-two-slits experiment, within macroscopic distances from diaphragm, the patterns are non-diffraction and gradually evolve to the diffraction-interference-hybrid patterns; (4) the diffraction-interference-hybrid patterns are angle-dependence. To interpret consistently above phenomena is the challenge to the existing wave theories of the physical optics. Advances in optical experiments demand new theory.