Neutron Compton scattering (NCS) results obtained from liquid hydrogen and hydrogen–deuterium mixtures at
20
K
are presented. The measurements have been repeated changing the scattering geometry and ...employing various experimental setups. The results exhibit the following striking effect. By comparing the recoil-peak intensities for H and D in the mixtures, a strong anomalous shortfall (up to ca. 30%) of the ratio of H and D cross-sections is found, which is rather independent of the scattering angle
θ. A related (but systematically
θ-dependent) anomaly is also observed in the ratio of the recoil-peak intensities of H and Al (the latter being due to the sample cell). This effect was previously observed in other materials, too, and it was proposed to be caused by short-lived quantum entanglement involving protons in condensed matter.
Scattering of neutrons in the 24–
150
keV
incident energy range from
H
2
O
relative to that of
D
2
O
and
H
2
O
–
D
2
O
mixtures was reported very recently. Studying time-of-flight integrated ...intensities, the applied experimental procedure appears to be transparent and may open up a novel class of neutron experiments regarding the “anomalous” scattering from protons, firstly observed in our experiment at ISIS in the 5–
100
eV
range. The keV-results were analyzed within standard theory, also including (1) multiple scattering and (2) the strong incident-energy dependence of the neutron–proton cross-section
σ
H
(
E
0
)
in this energy range. The analysis reveals a striking anomalous ratio of scattering intensity of
H
2
O
relative to that of
D
2
O
of about 20%, thus being in surprisingly good agreement with the earlier results of the original experiment at ISIS.
Very recently, a temperature dependent decrease of the protonic neutron scattering cross section aH in LiH using neutron Compton scattering (NCS) has been reported. The decrease of aH - which has ...been found in various materials using different experimental methods - is attributed to short-lived protonic quantum entanglement and it was suggested that the novel temperature dependence is due to the different coupling of the protons to the environment. The exact mechanism of the loss of coherence (i.e. decoherence) of the protonic quantum entangled states due to the interaction with the environment in condensed matter is not fully understood yet. To shed more light onto that, the NCS of LaH2 and LaH3 has been measured. While LaH2 is metallic, LaH3 is an isolator, thus providing completely different electronic environments the protons are coupled to. The experiment shows that aH is smaller for LaH3 than it is for LaH2. This result strongly suggest that the different couplings of the protons to the different electronic environments lead to different anomalies.
Decoherence of quantum entangled particles is observed in most systems, and is usually caused by system-environment interactions. Disentangling two subsystems A and B of a quantum system AB is ...tantamount to erasure of quantum phase relations between A and B. It is widely believed that this erasure is an innocuous process, which e.g. does not affect the energies of A and B. Surprisingly, recent theoretical investigations by different groups showed that disentangling two systems, i.e. their decoherence, can cause an increase of their energies. Applying this result to the context of neutron Compton scattering from H2 molecules, we provide for the first time experimental evidence which supports this prediction. The results reveal that the neutron-proton collision leading to the cleavage of the H-H bond in the sub-femtosecond timescale is accompanied by larger energy transfer (by about 3%) than conventional theory predicts. It is proposed to interpreted the results by considering the neutron-proton collisional system as an entangled open quantum system being subject to decoherence owing to the interactions with the “environment” (i.e., two electrons plus second proton of H2).
On the mechanism of proton conductivity in H3OSbTeO6 Boysen, Hans; Lerch, Martin; Fernandez-Alonso, Felix ...
The Journal of physics and chemistry of solids,
July 2012, 2012-7-00, 20120701, Letnik:
73, Številka:
7
Journal Article
Recenzirano
Pyrochlore-type H3OSbTeO6 is a remarkable proton conductor exhibiting an outstanding electrical conductivity even at ambient temperature. It consists of a three-dimensional interconnected (Sb,Te)O6 ...framework, built from randomly distributed corner-shared SbO6 and TeO6 octahedra, forming large cages in which the H3O+ ions are located. The dynamics of the caged species has been investigated by temperature-dependent neutron diffraction, quasielastic neutron scattering, and NMR experiments. Three types of motion may be discerned, namely, stochastic rotations of the H3O group around its 3-fold axis, jumps between four equivalent positions within the cage, and long-range inter-cage translational diffusion. The onset of ionic conductivity is clearly reflected by structural changes. Details of the complex diffusion mechanism are given.
► H3OSbTeO6 is an outstanding proton conductor. ► We investigated the dynamics of the caged hydronium ions as a function of temperature. ► Onset of proton conductivity is reflected by structural changes. ► A complex diffusion mechanism is observed.
Electron Compton scattering from methane and methane-d4 Cooper, G.; Hitchcock, A.P.; Chatzidimitriou-Dreismann, C.A. ...
Journal of electron spectroscopy and related phenomena,
3/2007, Letnik:
155, Številka:
1-3
Journal Article
Nuclei and electrons in condensed matter and/or molecules are usually entangled, due to the prevailing (mainly electromagnetic) interactions. However, the "environment" of a microscopic scattering ...system (e.g. a proton) causes ultrafast decoherence, thus making atomic and/or nuclear entanglement effects not directly accessible to experiments. However, our neutron Compton scattering experiments from protons (H-atoms) in condensed systems and molecules have a characteristic collisional time about 100–1000 attoseconds. The quantum dynamics of an atom in this ultrashort, but finite, time window is governed by non-unitary time evolution due to the aforementioned decoherence. Unexpectedly, recent theoretical investigations have shown that decoherence can also have the following energetic consequences. Disentangling two subsystems A and B of a quantum system AB is tantamount to erasure of quantum phase relations between A and B. This erasure is widely believed to be an innocuous process, which e.g. does not affect the energies of A and B. However, two independent groups proved recently that disentangling two systems, within a sufficiently short time interval, causes increase of their energies. This is also derivable by the simplest Lindblad-type master equation of one particle being subject to pure decoherence. Our neutron-proton scattering experiments with H2 molecules provide for the first time experimental evidence of this effect. Our results reveal that the neutron-proton collision, leading to the cleavage of the H-H bond in the attosecond timescale, is accompanied by larger energy transfer (by about 2–3%) than conventional theory predicts. Preliminary results from current investigations show qualitatively the same effect in the neutron-deuteron Compton scattering from D2 molecules. We interpret the experimental findings by treating the neutron-proton (or neutron-deuteron) collisional system as an entangled open quantum system being subject to fast decoherence caused by its "environment" (i.e., two electrons plus second nucleus of H2 or D2). The presented results seem to be of generic nature, and may have considerable consequences for various processes in condensed matter and molecules, e.g. in elementary chemical reactions.
In a recent paper by Blostein et al. (Physica B 304 (2001) 357) was presented a critical theoretical analysis of different procedures, with which data of deep inelastic neutron scattering (DINS) ...experiments are usually processed. One part of that criticism—which is experimentally tested in the present paper—claimed the existence of serious errors in the determined areas of overlapping DINS-peaks, in particular in the case of the considerable overlapping of the strong proton peak with the weak deuteron peak. Our experimental test presented here consists in the comparison of the D-peak areas determined from DINS-data of H/D mixed systems, taken in both the “forward” and the “backward” scattering directions. Since there is no H-peak in the “backward” scattering direction, the claimed error cannot occur in this regime. New experimental results from (A) pure D
2O, and (B) the equimolar H
2O/D
2O mixture, are presented. The liquids were contained in a Nb can. For both systems, it is shown that the D-peak areas in the “forward” and the “backward” scattering directions are essentially equal. This proves that the aforementioned criticism, although very stimulating, is of no relevance in the specific context of our (previous and present) DINS experiments. Moreover, the new experiments show that the cross-section of D is fully consistent with conventional expectations.
Recently, we reported the ‘anomalous’ neutron scattering behavior of protons in condensed systems, e.g. water, metallic hydrides, and organic materials as observed on the eVS instrument at ISIS. Very ...recently, Blostein et al. Physica B 304 (2001) 357 presented a theoretical investigation criticizing the convolution method used for the analysis of the data obtained on eVS. In particular, they criticize the expression of the experimentally observed spectral intensity as a convolution with the absorption peak of the analyzer foil. They conclude that the usually employed data analysis procedure fails in determining the inferred momentum distribution widths of the peaks and leads to incorrect values of peak areas in the case of two (or more) overlapping recoil peaks, in particular those of H and D. However, experimental results on metallic hydrides show very clearly that the objections concerning the peak areas are not relevant for the results and for the associated subfemtosecond quantum entanglement effect under consideration, thus supporting the validity of the convolution formalism for investigating peak areas on the eVS instrument.
The Comment by Mayers and Reiter criticizes our work on two counts. Firstly, it is claimed that the quantum decoherence effects that we report in consequence of our experimental analysis of neutron ...Compton scattering from H in gaseous H2 are not, as we maintain, outside the framework of conventional neutron scattering theory. Secondly, it is claimed that we did not really observe such effects, owing to a faulty analysis of the experimental data, which are claimed to be in agreement with conventional theory. We focus in this response on the critical issue of the reliability of our experimental results and analysis. Using the same standard Vesuvio instrument programs used by Mayers et al., we show that, if the experimental results for H in gaseous H2 are in agreement with conventional theory, then those for D in gaseous D2 obtained in the same way cannot be, and vice-versa. We expose a flaw in the calibration methodology used by Mayers et al. that leads to the present disagreement over the behaviour of H, namely the ad hoc adjustment of the measured H peak positions in TOF during the calibration of Vesuvio so that agreement is obtained with the expectation of conventional theory. We briefly address the question of the necessity to apply the theory of open quantum systems.
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