D in D2O
D(D2O) GA EVAL-DEC69 KOPPEL,HOUSTON
REF.1 (1978) DIST-MAY10 20100309
----JENDL-4.0 MATERIAL 11
-----THERMAL NEUTRON SCATTERING DATA
------ENDF-6 FORMAT
==================================================================
The data were taken from ENDF/B-VI.8.
==================================================================
TEMPERATURES = 296 350 400 450 500 600 800 1000 DEG K.
HISTORY
-------
THIS EVALUATION WAS PRODUCED AT GENERAL ATOMIC IN 1969 USING
THE GA CODE GASKET (SEE REF.1). IT WAS CONVERTED
TO ENDF-6 FORMAT AT LOS ALAMOS IN 1989. THE ONLY CHANGES
MADE TO THE CONTENTS WERE ADJUSTMENTS OF CROSS SECTIONS
TO MATCH THE ENDF/B-VI VALUES.
THEORY
------
WHEREAS HYDROGEN IS NEARLY A COMPLETELY INCOHERENT NEUTRON
SCATTERER, THE SCATTERERING FROM DEUTERIUM IS LARGELY COHERENT.
ALTHOUGH IT WOULD APPEAR THAT DUE TO THIS FACT A TREATMENT
OF D2O ANALOGOUS TO THE ONE USED FOR H2O WOULD BE INADEQUATE,
CALCULATIONS (REF. 2) HAVE SHOWN THAT BECAUSE OF A GREAT DEAL
OF CANCELLATION BETWEEN INTER AND INTRA-MOLECULAR INTERFERENCE
SCATTERING, INTEGRAL QUANTITIES LIKE THE TOTAL CROSS SECTION
OR THERMAL NEUTRON SPECTRA CAN ACTUALLY BE PREDICTED QUITE
ACCURATELY WITH AN INCOHERENT MODEL.
THEREFORE, THE SCATTERING LAW FOR D2O IS BASED ON A MODEL
QUITE SIMILAR TO THE ONE USED FOR THE GA EVALUATION OF H2O;
NAMELY, FREELY RECOILING D2O MOLECULES OF MASS 20. EACH
MOLECULE CAN UNDERGO TORSIONAL HARMONIC OSCILLATIONS (HINDERED
ROTATIONS) WITH A BROAD SPECTRUM OF DISTRIBUTED MODES. BETWEEN
0.025 AND 0.127 EV, THE ROTATION SPECTRUM IS TAKEN FROM THE
WORK OF HAYWOOD (REF. 3) JOINED TO A QUADRATIC LAW BELOW
0.025 EV. IN ADDITION, THERE ARE TWO INTERNAL VIBRATIONS AT
FREQUENCIES OF 0.142 AND 0.305 EV (THE FREQUENCIES ARE
APPROXIMATELY 1/SQRT(2) TIMES THE CORRESPONDING FREQUENCIES
FOR H2O AS EXPECTED FROM THE MASS RATIO) WITH MASSES OF 6 AND
3, RESPECTIVELY. THE TORSIONAL BAND IS NORMALIZED TO A MASS
OF 20/9. THE SCATTERING BY THE OXYGEN ATOMS IS NOT INCLUDED
IN THE TABULATED SCATTERING LAW DATA. IT SHOULD BE TAKEN INTO
ACCOUNT BY ADDING THE THE SCATTERING FOR FREE OXYGEN OF
MASS 16.
REFERENCES
----------
1. J.U.KOPPEL AND D.H.HOUSTON, REFERENCE MANUAL FOR ENDF
THERMAL NEUTRON SCATTERING DATA, GENERAL ATOMIC REPORT
GA-8774 REVISED AND REISSUED AS ENDF-269 BY THE NATIONAL
NUCLEAR DATA CENTER, JULY 1978.
2. J.U.KOPPEL AND J.A.YOUNG, NUKLEONIK 7, 408(1965).
3. B.C.HAYWOOD, "PROC. IAEA SYMP. ON PULSED NEUTRON RESEARCH",
KARLSRUHE, VOL. i, P.434(1965).