High-spin states in 40K investigated with the 26MG + 16O reaction

doi:10.1016/0375-9474(77)90153-1

Nuclear Physics A

Volume 285, Issue 1, 18 July 1977, Pages 167-188

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Abstract

Yrast levels in ⁴⁰K and ⁴⁰Ar have been investigated with the ²⁶Mg(¹⁶O, pnγ)⁴⁰K and ²⁶Mg(¹⁶O, 2pγ)⁴⁰Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The ⁴⁰K decay scheme involves new high-spin levels at E_tx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of $J^{π} = 5^{−}, 6^{+}, 8^{+}, 9^{+} and (8, 10)^{−}$ to the ⁴⁰K levels at E_x = 0.89, 2.88, 4.37, 4.88 and 6.23 and of $J^{π} = 4^{+} and 6^{+} to the^{40} Ar$ levels at E_x = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported.

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Cited by (17)

Nuclear Data Sheets for A=40
2017, Nuclear Data Sheets
The experimental nuclear structure data and decay data are evaluated for the known nuclides of mass 40 (Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti). Detailed evaluated nuclear structure information is presented with the best values recommended for level energies, half-lives, γ-ray energies and intensities, decay properties (energies, intensities and placement of radiations), and other spectroscopic data. The ⁴⁰Ca and ⁴⁰K nuclides remain as the most extensively studied from many different reactions and decays; no excited states are known in ⁴⁰Mg, ⁴⁰Al, ⁴⁰P and ⁴⁰Ti. This work supersedes the earlier full evaluation of A=40 by J. Cameron and B. Singh (2004Ca38).
Nuclear data sheets for A = 40
2004, Nuclear Data Sheets
Nuclear spectroscopic information for the known nuclides of mass 40 (Al,Si,P,S,Cl,Ar,K,Ca,Sc,Ti) has been evaluated. The principal sources of the adopted levels presented are Endt's evaluations (1990En08, 1978En02). The data sets for reactions and decays, including all available gamma-ray data, are based mostly on the original literature. There are no data available for the excited states in ⁴⁰Al, ⁴⁰Si, ⁴⁰P and ⁴⁰Ti. The identification and particle stability of ⁴⁰Mg are still uncertain, although search for this nuclide has been made (2002Lu09,2002No11,2003Pe31).
Energy levels of A = 21-44 nuclei (VII)
1990, Nuclear Physics, Section A
The experimentally determined properties of A = 21–44 nuclides are complied and evaluated with special emphasis on nuclear spectroscopy.
Separate tables for each of the nuclides reviewed present the available information about the following properties (in this order):
- •
  - excitation energies E_x,
- •
  - γ-ray branching ratios b(γ),
- •
  - γ-ray mixing ratios σ,
- •
  - lifetimes γ_m or widths Λ,
- •
  - neutron, proton, or α-particle resonances,
- •
  - partial widths,
- •
  - single-nucleon transfer reactions,
- •
  - beta-decay,
- •
  - arguments for spin and parity (J^π) and isospin (T) assignments.
For each nuclide a master table summarizing the “best” or adopted values for E_x, J^π; T and τ_m or Λ precedes the auxiliary tables listed above.
The review of each A-chain concludes with a discussion of isospin multiplets.
Figures are presented of the level schemes of all nuclei and, for each A-chain, an overview of the relative energies of the ground states and lowest analogue states of all nuclei in the chain.
Spectroscopy of 41K by thermal neutron capture in 40K
1984, Nuclear Physics, Section A
The γ-ray spectrum emitted after thermal neutron capture in ⁴⁰K has been studied at the ILL high flux reactor with curved crystal Bragg, pair and Ge(Li) spectometers. 585 transitions were assigned to the reaction ⁴⁰K(n, γ)⁴¹K and 490 of them were placed into a ⁴¹K level scheme; 68 new states are proposed. On the basis of γ-ray branches to states with established spin and parity, many new spin-parity assignments were made. The level energies up to 4 MeV were measured with a precision of 8–50 eV relative to the 411.8 keV ¹⁹⁸Au standard, those above 4 MeV with a precision of 50–100 eV. The spin of the capture state was found to be $I = 72$ ; the neutron binding energy was determined to E_B = 10095.25(10) keV. The level density of $I^{π} = 52^{±}, 72^{±}, 92^{±}$ states was analyzed in terms of the constant-temperature Fermi gas model. It was shown that in this spin window the level scheme is almost complete up to an excitation energy of 5 MeV.
High-spin states in 38K
1983, Nuclear Physics, Section A
High-spin states in ³⁸K are investigated with the ²⁴Mg(¹⁶O, pnγ)³⁸K reaction at $E(^{16} O) = 36–44 MeV$ . A recently developed Compton-suppression spectrometer with 120 msr solid angle and a pulsed beam are employed to study their γ-decay. For the E4 transition from the isomeric level at E_x = 3458 keV to the ground state a branching ratio of (0.15 ± 0.02)% is found. On the basis of angular distribution and polarization measurements, in which the delayed feeding component is eliminated, spin-parity assignments are obtained of J^π(2646 keV) = (2, 4)⁻, J^π(3420 keV) = (4, 6)⁻ and J^π(3458 keV) = (5, 7)⁺. Prompt-delayed and prompt γγ coincidence experiments are performed to locate high-spin levels above the isomer. Hitherto unobserved levels of high spin are found at E_x = 5254, 7397, 8693, 8747 and 10980 keV and assignments of J^π = (9⁺), (10⁻), (12⁻), (11⁻) and (13⁻) respectively, are suggested by weak-coupling considerations. The experimental results are compared with a large-scale shell-model calculation performed in a configuration space with a ²⁸Si core and ten active particles distributed over the ( $2 s_{12}, 1 d_{32}, 1 f_{72}, 2 p_{32})$ shells. The high-spin states appear to have a rather simple shell-model structure.
Improvement of the performance of a Compton-suppression spectrometer by minimizing the dead layer of the central Ge detector
1980, Nuclear Instruments and Methods
The performance of a Compton-suppression spectrometer is investigated for two different Ge crystals as central detector; a 126 cm³ Ge(Li) with a dead layer of 1.0 mm and a 90 cm³ HPGe with a dead layer of 0.22 mm. The thin dead layer HPGe gives a 32% improvement in the overall Compton suppression. Predictions of the influence of the dead-layer thickness by means of Monte Carlo calculations are in good agreement. The spectrometer is further tested with radioactive sources of ⁸⁸Y and ¹⁵²Eu and the in-beam reaction ²⁴Mg + (45 MeV)¹⁶O.

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Nuclear Physics A

Abstract

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Cited by (17)

Nuclear Data Sheets for A=40

Nuclear data sheets for A = 40

Energy levels of A = 21-44 nuclei (VII)

Spectroscopy of <sup>41</sup>K by thermal neutron capture in <sup>40</sup>K

High-spin states in <sup>38</sup>K

Improvement of the performance of a Compton-suppression spectrometer by minimizing the dead layer of the central Ge detector