Nuclear levels in 187W

doi:10.1016/S0375-9474(97)00148-6

Nuclear Physics A

Volume 619, Issues 1–2, 16 June 1997, Pages 1-48

https://doi.org/10.1016/S0375-9474(97)00148-6 Get rights and content

Abstract

Levels in ¹⁸⁷W have been studied up to 2.2 MeV with the (d, p) and (n, γ) reactions. The (d, p) studies were performed at deuteron energies of 24 and 28 MeV and at two angles of 30° and 50° by using the high resolution Q3D spectrograph in Munich. Primary and secondary γ-rays and γ-γ coincidences were studied with Ge detectors. The combination of these results with the previously known ones allows us to extend the existing level scheme and refine some of its structure assignments. Most of the low-lying states have been classified in terms of the Nilsson model with the extension of some vibrational degrees of freedom. The possibility for the coexistence of triaxial or oblate shapes in ¹⁸⁷W is observed in the form of anti-aligned states with a bandhead of $92^{−}$ at 364 keV. The polarization effects towards the triaxial shape produced by the odd neutron in specific Nilsson orbitals have been studied. The calculated polarization energies for some γ-driving orbitals are comparable with the prolate-oblate energy difference which indicates the possibility of the stabilization of triaxial or oblate shapes in these states.

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Levels of 188Re nucleus populated in thermal neutron capture reaction
2016, Nuclear Physics A
Levels of ¹⁸⁸Re populated in thermal neutron capture reaction with enriched ¹⁸⁷Re targets have been studied. Single γ-ray spectrum of ¹⁸⁸Re, measured with the high-resolution crystal diffraction spectrometer GAMS5, as well as γγ-coincidence experiments performed with high efficiency Ge detectors, allowed to develop model-independent level scheme of the doubly-odd ¹⁸⁸Re nucleus up to $\sim 1.5 MeV$ excitation energy. Analysis of the established ¹⁸⁸Re level scheme in terms of the quasiparticle-plus-rotor model indicates coexistence of axially-deformed and triaxial structures in the energy range above 400 keV.
Emission probabilities of some intense prompt γ rays of 24Na, 28Al, 52V, 56Mn, 60Co, 142Pr, 187W and 198Au with thermal neutron capture determined using γ rays following β decay
2012, Annals of Nuclear Energy
Citation Excerpt :
Concerning the other two γ-rays of 5261.7- and 5320.7-keV, the reasons of disagreement could not be made clear, but, it is possible that there are some contaminating γ rays from other W isotope in the results by Révay et al. (2004). This speculation was supported by the results by Bondarenko et al. (1997, 2008). Bondarenko et al., proposed two results in 1997 and 2008 by using the enriched sample (99.8%) of 186W.
Some emission probabilities of relatively intense or less contaminant prompt γ rays of ²⁴Na, ²⁸Al, ⁵²V, ⁵⁶Mn, ⁶⁰Co, ¹⁴²Pr, ¹⁸⁷W and ¹⁹⁸Au with thermal-neutron capture reactions were determined by successive measurement of γ rays following the β decay of produced radioisotopes, namely β-delayed γ rays. Prompt and β-delayed γ rays were measured with the same HPGe detector the efficiency of which is well determined for a wide energy range, from 0.1 to 11 MeV. The previously proposed values for ²⁴Na, ²⁸Al, ⁶⁰Co and ¹⁹⁸Au except for low energy, were generally in agreement with the present results, while those for ⁵²V, ⁵⁶Mn, ¹⁴²Pr and ¹⁸⁷W were not. The reasons for the disagreement are discussed in terms of the detection efficiencies of the detectors, the used nuclear data and the normalization procedure for determining prompt γ-ray intensities. The effectiveness of this method at checking the intensities of prompt γ rays is demonstrated.
Nuclear levels of 183W studied with (n,γ) and (d,p) reactions
2011, Nuclear Physics A
The level structure of ¹⁸³W has been studied using gamma–gamma coincidences from thermal neutron capture in ¹⁸²W accompanied with the reaction $(\vec{d}, p)$ . From these data and those of previous studies a total of 76 levels and about 490 connecting γ-transitions have been established for energies below 2.4 MeV. An analysis based on the standard distorted-wave Born approximation (DWBA) provides the lj-angular momentum transfers and spectroscopic factors for 36 levels up to 2.2 MeV excitation energy. A large number of particle transitions indicate an influence of strong mixing between particle and probably hole states. The extra exchange of phonons across the Fermi surface leads to a fine structure in the fragmentation of most single particle strengths and at the same time has the effect of breakdown of the individual properties of Nilsson states. The extracted $l = 1$ and 2 (d, p) sum below 2 MeV has about the same magnitude as in ^185,187W. It comprises a rather small fraction of the expected strengths. The observed states below 2 MeV are compared with predictions of the quasiparticle–phonon model. Of particular interest is the identification of “quasi-bands” with inverse spin sequence based on the state $9 / 2^{+}$ at 622.8 keV; this indicates some transition aspects from rigid rotors of light W to γ-soft nuclei in the Os-Pt region.
Low-lying levels of 188Re nucleus from γγ-coincidence measurements
2010, Nuclear Physics A
Low–high and low–low energy γγ-coincidences, following the ${}^{187}{Re} (n, γ) {}^{188}{Re}$ reaction with thermal neutrons, have been measured. Spectra have been recorded in the energy range from 50 to 2600 keV, and from 4500 to 6500 keV. The earlier known ¹⁸⁸Re level scheme is corrected and extended up to ∼800 keV excitation energy and 62 levels by including 20 new levels. For 11 levels, the earlier interpretation has been changed. The complete level scheme is presented for up to ∼400 keV energy and spins ⩽5. Core plus two-quasiparticles model calculations have been performed. Some ¹⁸⁸Re two-quasiparticle states display features indicating the nuclear shape phase transition from axial-deformation to γ-soft form.
Nuclear Data Sheets for A = 187
2009, Nuclear Data Sheets
Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for ¹⁸⁷Hf, ¹⁸⁷Ta, ¹⁸⁷W, ¹⁸⁷Re, ¹⁸⁷Os, ¹⁸⁷Ir, ¹⁸⁷Pt, ¹⁸⁷Au, ¹⁸⁷Hg, ¹⁸⁷Tl, ¹⁸⁷Pb, ¹⁸⁷Bi, and ¹⁸⁷Po. This evaluation for A = 187 supersedes the earlier one by R.B. Firestone (1991Fi02) published in Nuclear Data Sheets 62, 159 (1991) and the ¹⁸⁷Tl evaluation by C.M. Baglin (1999Ba24) published in Nuclear Data Sheets 86, 487 (1999).
Highlights of this publication are the following:
This evaluation includes first identifications of ¹⁸⁷Hf, ¹⁸⁷Ta (1999Be63, 2000PoZY) and ¹⁸⁷Po (2006An11) nuclides.
A B(E2)↑ = 0.080 12 was determined by 1967Bi10 for the 9/2+ state at 845 keV in ¹⁸⁷Re Coulomb Excitation. Using this B(E2) value and the adopted 845γ ray properties, a $T_{1 / 2} = 54$ fs 34 can be deduced for the 845 keV level of ¹⁸⁷Re. This T_1/2 yields a large $B(E2)(W.u.) \approx 1.3 \times 105$ for the 263γ (depopulating the same level) indicating either substantial unobserved feeding or incorrect g-ray branching intensities of this level.
The decay of g.s. and isomer of ¹⁸⁷Tl are poorly known (please see ¹⁸⁷Tl ε decay (51 s+15.60 s)).
Based on ¹⁹¹Po α decay studies, 2002An19 establishes a ¹⁸⁷Pb isomeric level energy at 2(15) keV and assigns $J π = 13 / 2 +$ for the ¹⁸⁷Pb g.s. and $J π = 3 / 2 -$ for the isomeric state (inverse of the systematics of odd-mass Pb nuclei in this region). From ¹⁸⁷Pb and ¹⁸⁷Pb^m mass measurements, 2005We11 determined the isomeric level energy at 33(13) keV.
Nuclear structure of 187W studied with (n, γ) and (d, p) reactions
2008, Nuclear Physics A
The level structure of ¹⁸⁷W has been studied using prompt and delayed gamma–gamma coincidences from thermal neutron capture in ¹⁸⁶W and also measuring the $(d, p)$ reaction. From these data and those of previous studies a total of 170 levels (121 connected by γ transitions) have been established for energies below 2.35 MeV. Some of these levels have been grouped into rotational bands built on 14 intrinsic states of quasi-particle and quasi-particle plus phonon character. Of particular interest has been the identification of “quasi bands” with inverse spin sequence based on the newly established isomeric $11 / 2^{+}$ state at 410.1 keV. Although the DWBA analysis permitted definite spin–parity assignments for most states a large number of particle transitions have “anomalous” angular distribution shapes with respect to the DWBA which indicate an influence of strong mixing between particle and probably hole states. The exchange of phonons across the Fermi surface leads to a fine structure in the extra fragmentation of most single particle strengths and, at the same time, it produces the effect of breakdown of individual properties of Nilsson states. The total extracted $l = 1$ , 2 and 3 $(d, p)$ strengths below 2 MeV have about the same magnitudes as in ¹⁸⁵W that comprise a rather small fraction of the expected strengths. The observed states below 2 MeV are compared with predictions of the quasi particle phonon model. The discussion focuses on transition aspects from rigid rotors of light W to γ-soft nuclei in the Os, Pt region.

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²: Present address: TeleMedia P.O. Box 256, LV-1047 Riga, Latvia.

³: Present address: Sektion Physik, Universität München, D-85748 Garching, Germany.

⁴: Present address: Max-Planck Institut für Extraterrestische Physik, D-85748 Garching, Germany.

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Nuclear Physics A

Abstract

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Cited by (12)

Levels of <sup>188</sup>Re nucleus populated in thermal neutron capture reaction

Emission probabilities of some intense prompt γ rays of <sup>24</sup>Na, <sup>28</sup>Al, <sup>52</sup>V, <sup>56</sup>Mn, <sup>60</sup>Co, <sup>142</sup>Pr, <sup>187</sup>W and <sup>198</sup>Au with thermal neutron capture determined using γ rays following β decay

Nuclear levels of <sup>183</sup>W studied with (n,<sup>γ</sup>) and (d,p) reactions

Low-lying levels of <sup>188</sup>Re nucleus from γγ-coincidence measurements

Nuclear Data Sheets for A = 187

Nuclear structure of <sup>187</sup>W studied with (n, γ) and (d, p) reactions