H in H2O
h(h2o) LANL EVAL-apr93 MACFARLANE
ref. 4 (1994) DIST-MAY10 20100309
----JENDL-4.0 MATERIAL 1
-----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 generated at the los alamos national
laboratory (april 93) using the leapr code. the physical
model is very similar to the one used at general atomic
in 1969 to produced the original endf/b-iii evaluations
(see ref. 1). the alpha and beta grids were extended, and
the constants were changed to match the endf/b-vi values.
theory
------
water is represented by freely recoiling h2o molecules of
mass 18. each molecule can undergo torsional harmonic
oscillations (hindered rotations) with a broad spectrum of
distributed modes. between 0.04 and 0.165 ev, the rotation
spectrum is taken from the work of haywood and thorson (ref. 2)
joined to a quadratic law below 0.04 ev. In addition, there
are two internal vibrations at frequencies of 0.205 and 0.48 ev
taken over from the Nelkin model (ref. 3) with slightly
readjusted masses of 6 and 3, respectively. the torsional band
is normalized to a mass of 18/8. 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. b.c.haywood and j.m.thorson, "proc. conf. on neutron
thermalization", brookhaven (1962).
3. m.s.nelkin, phys. rev. 119, 741(1960).
4. r.e.macfarlane, new thermal neutron scattering files for
endf/b-vi release 2, los alamos national laboratory report
LA-12639-MS (ENDF-356) March 1994.