Anomalous quasi-elastic scattering of hydrogen isotopes

WHO:  Glyn Cooper, Adam Hitchcock, BIMR, McMaster University;  
            Aris Chatzidimitriou-Dreismann, Chemistry, Technical University, Berlin
             
 
WHERE:  ABB-332  McVAHRES - McMaster Variable Angle High Resolution Electron Scattering
 
WHEN:   2007               POSTED:  19 Feb 2008

WHAT:  At large scattering angles (>60 deg) and moderate or high impact energies (>2 keV) the atoms of a gas phase molecule (or a solid) scatter the electron beam independently from their neighbours, resulting in quasi-elastic electron scattering which can give rise to peaks separated by several eV in energy. The positions of these peaks are accurately predicted by simple conservation of energy and momentum considerations (Rutherford formula). The intensity should be proportional to the square of the atomic number and number of that type of atom in the molecule. Thus the signal for HD and a 50:50 mixture of H2:D2 should be the same. However, our measurements show a 30% deficiency of intensity of H2 relative to HD or D2 (see figure). The origin of this anomaly is not yet determined, but may be related to quantum entanglement of the incident electron and target nucleus on the attosecond time scale of the scattering. Further studies are underway to see if this relatively simply macroscopic scattering measurement can provide insight into quantum entanglement and the process of decoherence

REFERENCE: G. Cooper, A. P. Hitchcock and C. A. Chatzidimitriou-Dreismann, Anomalous quasi-elastic electron scattering from single H2, D2 and HD molecules at large momentum transfer: Indications of Nuclear Spin Effects, Phys.l Rev. Letts 100 (2008) 043204-(1-4).