The goal of this proposal for beam time on MARI (direct geometry) is to independently confirm (or refute) our observation using VESUVIO (indirect geometry) of a novel quantum phenomenon, namely a ¿quantum heating¿ effect in neutron Compton scattering (NCS) from H in H2, in which the energy transfer is 2¿3% larger than can be explained by conventional neutron scattering theory. This surprising effect can be interpreted by considering the neutron¿proton collisional system as an entangled open quantum system subject to ultrafast decoherence owing to interactions with the "environment" (i.e., two electrons plus the second proton of H2). We propose to compare the positions of the recoil peaks of H in H2 and D in D2 at constant Q with initial energy 40 eV. Novel physical insights into ultrafast scattering quantum dynamics are expected.