Breakdown of the Born-Oppenheimer description explains neutron Compton-scattering anomaly

Abstract

Several neutron Compton scattering experiments reveal an apparent drop of the proton cross section when the collision time q is around 1 fs. Such small q corresponds to a large energy spread of the proton wave packet after collision, allowing it to access excited electronic levels. This nonadiabatic excitation of electrons leads to a distortion of the shape of the neutron scattering response function with some redistribution of intensity at energies higher than the nuclear recoil energy and a slight shift of the main neutron intensity peak to lower energies.

Interpretation of the hydrogen anomaly in neutron and electron compton scattering

“…The existence of these anomalies still seems to remain valid in spite of extensive searches for errors in detection or data interpretation [4,5]. Major efforts have also been spent on different theoretical interpretations [6][7][8][9][10] of the intensity loss, so far without reaching a consensus about its origin. The proposed explanations fall into two classes: In one of these (called non-BornOppenheimer), it is assumed that the recoil energy and momentum are shared between the proton and an electron in the eV range, which leads to intensity reduction at the normal position of the Compton peak [6,7].…”

“…Major efforts have also been spent on different theoretical interpretations [6][7][8][9][10] of the intensity loss, so far without reaching a consensus about its origin. The proposed explanations fall into two classes: In one of these (called non-BornOppenheimer), it is assumed that the recoil energy and momentum are shared between the proton and an electron in the eV range, which leads to intensity reduction at the normal position of the Compton peak [6,7]. The other class of theories is based on quantum entanglement between the protons, either caused by interaction with a common electronic field [3 (p 555), 8] during scattering or through the antisymmetrization rules valid for scattering on identical particles [9,10].…”

Elastic electron scattering from methane at high momentum transfer

“…Chatzidimitriou-Dreismann et al 1997 or AbdulRedah and Chatzidimitriou-Dreismann 2002), deviations that were interpreted as a sign of the quantum nature (in particular attosecond entanglement) of protons in matter. The interpretation of these measurements remains however highly controversial (Karlsson and Lovesey 2000, Cowley 2003, Karlsson 2003, Reiter and Platzman 2005, Gidopoulos 2005, Chatzidimitriou-Dreismann 2005, ChatzidimitriouDreismann and Stenholm 2007 and a consensus on the cause of the anomalous hydrogen intensity has not been reached. Thus our present understanding of high momentum-transfer collisions (both in neutrons and in electron scattering) is far from complete.…”

Anomalous neutron Compton scattering cross section in zirconium hydride

“…On the one side, there are different theoretical models [13,14] which are consistent with the FMSR. On the other side, as pointed out in Ref.…”

“…Several theoretical models have been suggested to explain this striking effect. They propose the existence of short-lived quantum entanglement of protons in condensed matter [10][11][12] and/or refer to the breakdown of the Born-Oppenheimer approximation during the scattering process [12][13][14]. * Corresponding author.…”