Theory of Cold Neutron Scattering by Homonuclear Diatomic Liquids: I. Free Rotation

Sears, V. F.

doi:10.1139/p66-108

Cited by 201 publications

(123 citation statements)

References 18 publications

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“…In this case, the observed signal is proportional to the energy integral below the resolution-broadened rotational peak. Taking into account the quantum-mechanical form factor of the para-H 2 molecule, 18 the scattered intensities are proportional to…”

Section: Resultsmentioning

confidence: 99%

Solidpara-hydrogen as the paradigmatic quantum crystal: Three observables probed by ultrahigh-resolution neutron spectroscopy

et al. 2012

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Quantum crystals are characterized by zero-point-energy motions large enough to explore the details of the interaction potential beyond the harmonic approximation even at zero temperature. By making recourse to ultrahighresolution neutron spectroscopy, we have probed simultaneously three observables sensitive to anharmonic effects in solid para-H 2 over a wide temperature range, namely, Bragg scattering, molecular root-mean-square displacements, and the spectral linewidth of the J = 0 → 1 rotational transition which, on average, amounts to a half-width at half-maximum of 1.8 ± 0.2 μeV. These three quantities show no measurable variation with temperature, thus signaling the existence of a fully expanded crystal across the entire solid phase. Our results provide unambiguous experimental evidence for the intrinsic quantum character of this fundamental molecular solid.

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Section: Resultsmentioning

confidence: 99%

Solidpara-hydrogen as the paradigmatic quantum crystal: Three observables probed by ultrahigh-resolution neutron spectroscopy

et al. 2012

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“…15 The expression for d /d⍀ ͑up to the first order in angular momentum transfers͒ can be derived from it as…”

Section: Estimation Of Ortho-hydrogen Contentsmentioning

confidence: 99%

“…where b (ϩ) ϭ1.0817ϫ10 Ϫ14 m and b (Ϫ) ϭϪ4.742 ϫ10 Ϫ14 m are the proton-scattering lengths in the triplet and singlet states respectively, 16 rϭ0.742 Å is the mean distance between hydrogen nuclei in the molecule, 15 and j ᐉ are the spherical Bessel functions of ᐉ-th order. S(Q) is the molecular structure factor that in the limit Q→0 has the thermodynamic limit 0.054.…”

Section: Estimation Of Ortho-hydrogen Contentsmentioning

confidence: 99%

“…The functions f 1 and f 2 , are obtained from the integral of the incoherent scattering law over the allowed kinematic range of out experiment. 15 Based on recoil scattering results 18 we will describe the incoherent scattering law as that of a gas at 63 K. In such a way, the second and third terms of Eq. ͑13͒ contribute with an inelastic pedestal as shown in Fig.…”

Section: Para-hydrogen Differential Cross Sectionmentioning

confidence: 99%

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Static structure factor of liquid parahydrogen

et al. 2004

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The single-differential neutron-scattering cross section of liquid parahydrogen has been measured at 15.2 K and 2 bars of applied pressure by means of low-energy neutron diffraction. Our experimental conditions enable the direct observation of the peak of the liquid structure factor and therefore largely improve the signal-to-noise ratio with respect to measurements carried out using higher-energy neutron diffraction. This avoids the need of performing corrections of approximate nature to the measured cross section that is dominated by molecular rotational components if measured by conventional neutron diffraction.

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“…This fact implies that the double-differential neutron scattering cross-section, (dσ 2 /dΩdE ), is separable in the sum of two convolution products between COM and roto-vibrational parts, and, moreover, that the latter are substantially identical to the equivalent quantities observed in the gas phase [51,52]:…”

Section: The Theoretical Point Of Viewmentioning

confidence: 99%

Mean Kinetic Energy and Final State Effects in Liquid Hydrogens From Inelastic Neutron Scattering

Corradi¹,

Colognesi²,

Celli³

et al. 2003

Condens. Matter Phys.

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We have measured, using the TOSCA spectrometer at ISIS, the neutron scattering spectrum of liquid para-hydrogen ( T = 19.3 K and n = 25.4 nm ). From the high-energy region of the spectrum, namely 40 meV < ω < 1 eV, where the incoherent approximation for the center-of-mass motion applies, we have been able to extract the translational mean kinetic energy, which, as expected, turns out to be rather different from the classical values. However, significant deviations from the impulse approximation have been detected and the inclusion of some correction terms (accounting for the so-called final state effects) had to be accomplished in order to accurately describe the experimental spectra. The comparison of the present mean kinetic energy values with the available experimental and simulated data in the literature is quite good and confirms the excellent performances of TOSCA in the spectroscopic analysis of the condensed phases of liquid hydrogens.

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Theory of Cold Neutron Scattering by Homonuclear Diatomic Liquids: I. Free Rotation

Cited by 201 publications

References 18 publications

Solidpara-hydrogen as the paradigmatic quantum crystal: Three observables probed by ultrahigh-resolution neutron spectroscopy

Solidpara-hydrogen as the paradigmatic quantum crystal: Three observables probed by ultrahigh-resolution neutron spectroscopy

Static structure factor of liquid parahydrogen

Mean Kinetic Energy and Final State Effects in Liquid Hydrogens From Inelastic Neutron Scattering

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