192
P. Koehler et al.
Table 1 Gaussian γ distribution parameters from ML analysis of the data (row 3) and NSM
calculations (rows 4–8). σ G is the standard deviation of the assumed Gaussian distribution
Case
γ J = 1 − − γ J = 2 (meV)
σ G (meV)
J = 1
J = 2
Data
21.8 ± 4.9
24.1 ± 3.1
16.3 ± 1.8
Oslo
7.7
14.8
12.5
A1
11.4
13.3
10.4
A2
13.4
22.2
14.7
A3
14.8
18.8
12.8
A4
13.5
23.7
16.6
4 Conclusions
Distributions of total radiation widths for 197 Au neutron resonances were obtained
from simultaneous R-matrix analysis of new data from DICER as well as previous
data from n_TOF and GELINA. These data were compared to calculated distributions in the framework of the NSM using published NLDs and PSFs measured
using the Oslo technique. There were significant differences between the measured
and calculated distributions. We obtained agreement with the data by adjusting the
spin distribution of the NLD. As far as we know, the spin distribution is otherwise
poorly constrained, except at very low excitation in 198 Au. The technique we used is
applicable to other nuclides for which there are high-quality neutron resonance data
and could be used to obtain much better constraints on the nuclear spin distribution
as a function of excitation energy. As the spin distribution affects the shapes of
the NLD and PSF extracted using the Oslo technique, this work could have broad
implications.
References
1. A.C. Larsen et al., Analysis of possible systematic errors in the Oslo method. Phys. Rev. C 83,
034315 (2011)
2. P.E. Koehler et al., Extreme nonstatistical effects in γ decay of 95 Mo neutron resonances, Phys.
Rev. C 88, 041305(R) (2013)
3. F. Giacoppo et al., Level densities and thermodynamical properties of Pt and au isotopes. Phys.
Rev. C 90, 054330 (2014)
4. F. Giacoppo et al., γ decay from the quasicontinuum of 197,198 Au. Phys. Rev. C 91, 054327
(2015)
5. I. Sirakov et al., Results of total cross section measurements for 197 Au in the neutron energy
region from 4 to 108 keV at GELINA. Eur. Phys. J. A 49, 144 (2013)
6. C. Massimi et al., 197 Au(n,γ) cross section in the resonance region. Phys. Rev. C 81, 044616
(2010)
7. Koehler, P. E.: Total Cross Sections as a Surrogate for Neutron Capture, los Alamos National
Laboratory Report LA-UR-14-21466 (2014)
8. D.A. Brown et al., ENDF/B-VIII.0. Nuclear Data Sheets 148, 1 (2018)
P. Koehler et al.
Table 1 Gaussian γ distribution parameters from ML analysis of the data (row 3) and NSM
calculations (rows 4–8). σ G is the standard deviation of the assumed Gaussian distribution
Case
γ J = 1 − − γ J = 2 (meV)
σ G (meV)
J = 1
J = 2
Data
21.8 ± 4.9
24.1 ± 3.1
16.3 ± 1.8
Oslo
7.7
14.8
12.5
A1
11.4
13.3
10.4
A2
13.4
22.2
14.7
A3
14.8
18.8
12.8
A4
13.5
23.7
16.6
4 Conclusions
Distributions of total radiation widths for 197 Au neutron resonances were obtained
from simultaneous R-matrix analysis of new data from DICER as well as previous
data from n_TOF and GELINA. These data were compared to calculated distributions in the framework of the NSM using published NLDs and PSFs measured
using the Oslo technique. There were significant differences between the measured
and calculated distributions. We obtained agreement with the data by adjusting the
spin distribution of the NLD. As far as we know, the spin distribution is otherwise
poorly constrained, except at very low excitation in 198 Au. The technique we used is
applicable to other nuclides for which there are high-quality neutron resonance data
and could be used to obtain much better constraints on the nuclear spin distribution
as a function of excitation energy. As the spin distribution affects the shapes of
the NLD and PSF extracted using the Oslo technique, this work could have broad
implications.
References
1. A.C. Larsen et al., Analysis of possible systematic errors in the Oslo method. Phys. Rev. C 83,
034315 (2011)
2. P.E. Koehler et al., Extreme nonstatistical effects in γ decay of 95 Mo neutron resonances, Phys.
Rev. C 88, 041305(R) (2013)
3. F. Giacoppo et al., Level densities and thermodynamical properties of Pt and au isotopes. Phys.
Rev. C 90, 054330 (2014)
4. F. Giacoppo et al., γ decay from the quasicontinuum of 197,198 Au. Phys. Rev. C 91, 054327
(2015)
5. I. Sirakov et al., Results of total cross section measurements for 197 Au in the neutron energy
region from 4 to 108 keV at GELINA. Eur. Phys. J. A 49, 144 (2013)
6. C. Massimi et al., 197 Au(n,γ) cross section in the resonance region. Phys. Rev. C 81, 044616
(2010)
7. Koehler, P. E.: Total Cross Sections as a Surrogate for Neutron Capture, los Alamos National
Laboratory Report LA-UR-14-21466 (2014)
8. D.A. Brown et al., ENDF/B-VIII.0. Nuclear Data Sheets 148, 1 (2018)