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Title: Comment on 'Anomalous neutron Compton scattering from molecular hydrogen'

Abstract

Claims in the paper by Chatizidimitiou-Dreismann et al. [Phys. Rev. B 72, 054123 (2005)] that our analysis of the keV neutron scattering data is incorrect are shown to be wrong. Their analysis neglects the effect of the neutron attenuation in the relatively thick samples, thus creating an artificial anomaly of {approx}21% in the scattering intensity ratio of H{sub 2}O relative to that of D{sub 2}O.

Authors:
 [1];  [2]; ;  [3]
  1. Physics Department, Ben-Gurion University of the Negev, Beer-Sheva (Israel)
  2. (United States)
  3. Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)
Publication Date:
OSTI Identifier:
20976679
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevB.75.057101; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATTENUATION; COMPTON EFFECT; HEAVY WATER; HYDROGEN; KEV RANGE; NEUTRON DIFFRACTION; NEUTRONS

Citation Formats

Moreh, R., Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180, Block, R. C., and Danon, Y. Comment on 'Anomalous neutron Compton scattering from molecular hydrogen'. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.057101.
Moreh, R., Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180, Block, R. C., & Danon, Y. Comment on 'Anomalous neutron Compton scattering from molecular hydrogen'. United States. doi:10.1103/PHYSREVB.75.057101.
Moreh, R., Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180, Block, R. C., and Danon, Y. Thu . "Comment on 'Anomalous neutron Compton scattering from molecular hydrogen'". United States. doi:10.1103/PHYSREVB.75.057101.
@article{osti_20976679,
title = {Comment on 'Anomalous neutron Compton scattering from molecular hydrogen'},
author = {Moreh, R. and Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180 and Block, R. C. and Danon, Y.},
abstractNote = {Claims in the paper by Chatizidimitiou-Dreismann et al. [Phys. Rev. B 72, 054123 (2005)] that our analysis of the keV neutron scattering data is incorrect are shown to be wrong. Their analysis neglects the effect of the neutron attenuation in the relatively thick samples, thus creating an artificial anomaly of {approx}21% in the scattering intensity ratio of H{sub 2}O relative to that of D{sub 2}O.},
doi = {10.1103/PHYSREVB.75.057101},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 5,
volume = 75,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 2007},
month = {Thu Feb 01 00:00:00 EST 2007}
}
  • Claims in a Comment by R. Moreh et al. [Phys. Rev. B 75, 057101 (2007)] that their analysis of the keV neutron scattering data is correct and yields conventional results are shown to be wrong. Here we show that accounting for the neutron attenuation in the relatively thick samples, but neglecting the strong anisotropic distribution of double scattered neutrons from protons, creates an artificial and faulty decrease of about 19% in the theoretically predicted scattering intensity ratio of H{sub 2}O relative to that of D{sub 2}O.
  • Application of neutron Compton scattering, which operates in the attosecond time scale, to (a) the equimolar H{sub 2}-D{sub 2} mixture and (b) the mixed-isotope system HD (liquids, both at 20 K), reveals a strong anomalous shortfall (about 30%) of the ratio R={sigma}{sub H}/{sigma}{sub D} of H and D cross sections. This striking effect is similar to that observed in liquid H{sub 2}O-D{sub 2}O mixtures [C. A. Chatzidimitriou-Dreismann et al., Phys. Rev. Lett. 79, 2839 (1997)]. Crucially, the shortfall of R is equal in both samples (a) and (b). This result demonstrates that quantum exchange correlations of identical nuclei play nomore » significant role in this effect, thus refuting corresponding theoretical models claiming its interpretation. In contrast, our findings are consistent with alternative theoretical models, in which attosecond dynamics of electronic degrees of freedom (via violation of the Born-Oppenheimer approximation) is considered to participate significantly in the dynamics of an elementary neutron-proton (-deuteron) scattering process. Possible implications for attosecond chemical dynamics, e.g., the onset of bond breaking, are mentioned.« less
  • Cited by 4
  • A shortfall of the scattering intensity from protons has been observed in liquids (water, benzene, etc.) and solids (metal hydrogen systems, organic polymers, etc.) using neutron Compton scattering (NCS). However, the suitability of the conventional NCS data reduction scheme, used to obtain the scattering intensities, based on the convolution approximation (CA) of the nuclear momentum distribution with the instrument resolution function has been questioned. In the present work the commonly used data reduction scheme is compared to a model-free approach [B. Dorner, J. Neutron Res. (to be published)] that is independent of the form of the momentum distribution and themore » resolution function. Specifically, the ratios of the scattering cross section density of H to C are presented for polyethylene. The model-free approach is shown to lead to the same results as for experimental data published earlier and treated with the CA thus addressing a great part of the previous comments.« less
  • Neutron powder diffraction and magnetic Compton scattering measurements were conducted for ferromagnetic CaRu{sub 0.85}Fe{sub 0.15}O{sub 3} at temperatures between 10 and 300 K. Anomalous volume expansion was observed in the neutron diffraction measurement below the Curie temperature (85 K), and Invar-like behavior was observed below 40 K. However, no structural phase transition was observed down to 10 K. The strong correlation between the volume expansion, {delta}V, and the square magnetization, M{sup 2}, suggests that the anomalous volume expansion is due to the magnetovolume effect that is caused by the occurrence of ferromagnetism. The magnetic Compton scattering experiments revealed the existencemore » of a magnetic moment on Ru and the antiferromagnetic configuration of Fe and Ru moments. The formation of a ferrimagnetic order through the induction of the magnetic moment on the Ru ion is a possible reason for the anomalous volume expansion observed for CaRu{sub 0.85}Fe{sub 0.15}O{sub 3}.« less