Parameters and gamma-ray spectra of neutron resonances in the isotopes of mercury

doi:10.1016/0029-5582(60)90032-8

Nuclear Physics

Volume 21, November–December 1960, Pages 66-98

https://doi.org/10.1016/0029-5582(60)90032-8 Get rights and content

Abstract

The Argonne fast chopper has been used to study the neutron resonances of mercury. The neutron transmissions of five samples of normal mercury and six isotopically enriched samples were measured in the energy interval from 10 to 30 000 eV. Twenty-eight resonances were isotopically identified and parameters, including the spin, were determined for most of them. Average values of level spacings, radiations widths, and neutron strength functions were derived from the individual parameters. The spacings and radiation widths exhibit the expected rapid increase as the doubly closed shell is approached. Unexpectedly, the total radiation widths of different resonances of Hg²⁰¹ are found to fluctuate by a larger factor than has been previously observed in any other nuclear species. The gamma-ray spectra and the multiplicity of gamma rays from capture in these resonances were measured and both quantities were found to differ from resonance to resonance in a way that is consistent with the fluctuations in the widths. Seven high-energy gamma rays were resolved in the capture gamma-ray spectra of three resonances in Hg²⁰¹. The absolute intensities of the transitions were determined by a least-squares fit of the data to an experimentally determined line shape. It was found that these high-energy transitions are on the average enhanced, relative to those of lower energy, by about a factor of 15 beyond the usual E_γ³ law. The remainders obtained by subtracting the partial widths of the seven high-energy transitions from the total radiation widths are constant, within errors, for the three resonances investigated. This indicates that the fluctuations in the total radiation width are the result of fluctuations in the intensities of the transitions of highest energy. The observed magnitude of the fluctuations is shown to be consistent with that expected from random fluctuations of the partial radiation widths.

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Cited by (15)

Nuclear Data Sheets for A = 199
2007, Nuclear Data Sheets
Nuclear spectroscopic information for known nuclides of mass number 199 (Os,Ir,Pt,Au,Hg,Tl,Pb,Bi,Po,At,Rn,Fr) with Z = 76 to 87 and N = 123 to 112 have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No excited state data are available for ¹⁹⁹Os and ¹⁹⁹Fr, and very little information is available for levels in ¹⁹⁹Ir, ¹⁹⁹Rn and ¹⁹⁹At. The decay of ¹⁹⁹Ir to ¹⁹⁹Pt has not been studied. The decay of the 90-min activity of ¹⁹⁹Pb to ¹⁹⁹Tl is known in detail but remains unpublished in the open literature, while the decay of the 12.2-min isomer remains mostly unknown. The decays of the two activities of ¹⁹⁹Tl to ¹⁹⁹Pb are not known as separate decay scheme for each of the activities, thus only a composite decay scheme is presented. Similar is the case for the decay of the two activities of ¹⁹⁹Po to ¹⁹⁹Bi. In (³He,d) and (α,t) studies for ¹⁹⁹Au, disagreements are found between two independent contemporary studies. The most detailed structure known is for ¹⁹⁹Pb with five magnetic-rotational (MR) dipole bands together with many other dipole bands which are of probable multi-quasiparticle nature. This work supersedes previous evaluations of A = 199 published in update mode by 1994Ar13; as full A-chain updates by 1988Sc02, 1978Ha12 and 1971Le37; and a mid-stream update of ¹⁹⁹Pb nuclide by 2001Si44.
Nuclear data sheets for A = 202
1997, Nuclear Data Sheets
Nuclear data sheets for A = 202
1987, Nuclear Data Sheets
Nuclear data sheets for A = 202
1978, Nuclear Data Sheets
Resonance neutron capture in 198,199,201Hg
1975, Nuclear Physics, Section A
Partial radiation widths of γ-rays of energies E_γ > 4.1 MeV following capture of neutrons with E_n < 211 eV have been measured in ¹⁹⁹Hg, ²⁰⁰Hg and ²⁰²Hg. Gamma-ray tables and decay schemes are given. Gamma-ray strength functions and level density distributions are derived. Departures from statistical behaviour are observed in ¹⁹⁹Hg. It is found that the energy dependence of the level density below 3 MeV differs in functional form in the three isotopes.
P-wave neutron resonances in 203Tl and 205Tl
1972, Nuclear Physics, Section A
Neutron-transmission measurements on a thick sample of normal thallium reveal weak resonances at 38.0 and 44.6 eV. Neutron-capture capture γ-ray measurements by Bartholomew et al. show that the 39 eV resonance belongs to ²⁰³Tl and the 45 eV resonance to ²⁰⁵Tl. Parameters for the new resonances are obtained by curve-fitting the transmission data. The small values of the neutron widths indicate that both resonances are almost surely excited by p-waves.

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^†: Work performed under the auspices of the U.S. Atomic Energy Commission.

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Nuclear Physics

Abstract

References (30)

Nuclear Physics

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Cited by (15)

Nuclear Data Sheets for A = 199

Nuclear data sheets for A = 202

Nuclear data sheets for A = 202

Nuclear data sheets for A = 202

Resonance neutron capture in <sup>198,199,201</sup>Hg

P-wave neutron resonances in <sup>203</sup>Tl and <sup>205</sup>Tl