1-H - 1
1-H - 1 LANL EVAL-OCT05 G.M.Hale
DIST-MAY10 20080703
----JENDL-4.0 MATERIAL 125
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
HISTORY
08-07 All data were taken from ENDF/B-VII.0.
Compiled by K.Shibata (jaea).
******************************************************************
2200m/s Sig (b) res. integ. (b) [0.5 to 2.0e+7 eV]
total 20.768 -
elastic 20.436 -
capture 0.332 0.1492
******************************************************************
****************************************************************
The new R-matrix analysis of the N-N system on which the ENDF/B-
VII evaluation for 1H is based differs from the previous one use
for ENDF/B-VI in several respects. Firstly, the n-p capture
reaction (MT=102), and its inverse, deuteron photo-
disintegration, were a part of the analysis, rather than added
later as before. The analysis used a new method for including
photon channels in R-matrix theory [1], which gave a better
description of the E1 transitions, in particular. The data for
these reactions are mostly integrated and differential cross
sections, but some information about polarizations was also
included. The thermal capture cross section was taken to be
332.0 mb, as was the recommendation from preliminary data
testing. Good agreement was obtained with recent cross-section
measurements [2,3] by astrophysical groups in the 20-550 keV
range, as well as with earlier measurements that had been done
mostly as photo-disintegration experiments at energies below 14
MeV.
The new analysis includes several additional measurements of the
total cross section (MT=1). The evaluated cross section
deviates at most by about -0.5% around 10 MeV from that of
ENDF/B-VI. The estimated uncertainty of the MT=1 cross section
is given at 2 MeV steps in the following table:
En Uncert. (%)
0 0.20
2 0.22
4 0.30
6 0.36
8 0.44
10 0.50
12 0.49
14 0.46
16 0.40
18 0.35
20 0.30
For n-p scattering (MT=2), new information was included about the
low-energy cross sections (MF=3) and about the angular
distributions (MF=4). A new measurement of the angular
distribution at 10 MeV [4], plus corrections to earlier data at
14 MeV, moved the back-angle asymmetry in the 10-14 MeV range to
values that lie between those obtained for ENDF/B-V and ENDF/B-
VI. The addition of the latest value of the thermal coherent
scattering length [5] had the interesting effect of reducing the
"zero-energy" scattering cross section somewhat to agree
perfectly with an earlier measurement by Houk [6], and disagree
with the later, more precise, value of Dilg [7]. The
covariances for MT=2 will be added later, but the uncertainties
on the integrated cross section should be similar to those
listed above for the total cross section.
REFERENCES
[1] G. M. Hale and A. S. Johnson, Proc. 17th Int. IUPAP Conf. on
Few-Body Problems in Physics, 5-10 June 2003, Durham NC, W.
Gloeckle and W. Tornow, eds., Elsevier B.V., pp. S120-S122
(2004).
[2] T. S. Suzuki et al., Astrophys. Lett. 449, L59 (1995).
[3] Y. Nagai et al., Phys. Rev. C 56, 3173 (1997).
[4] N. Boukharouba et al., Phys. Rev. C 65, 014004 (2002).
[5] K. Schoen et al., Phys. Rev. C 67, 044005 (2003).
[6] T. L. Houk, Phys. Rev. C 3, 1886 (1971).
[7] W. Dilg, Phys. Rev. C 11, 103 (1975).
****************************************************************