Shell-model calculations on A = 38 nuclei

doi:10.1016/0375-9474(69)90902-6

Nuclear Physics A

Volume 123, Issue 1, 13 January 1969, Pages 225-240

https://doi.org/10.1016/0375-9474(69)90902-6 Get rights and content

Abstract

The shell model is used to investigate properties of levels in the A = 38 nuclei.

An inert ²⁸Si core with a residual two-particle interaction between the outer nucleons is assumed. The negative parity states are described by a closed $2 s_{12}$ shell, five nucleons in the $1 d_{32}$ shell and one nucleon in the $1 f_{72} or 2 p_{32}$ shell. For the positive parity states, all configurations in the $2 s_{case12} and 1 d_{32}$ shell are taken into account. The effective two-particle interaction is chosen to be a modified surface delta interaction. The four parameters of this effective interaction are determined in a least-squares fit to the excitation energies of 15 nuclear levels. The rms deviation of the calculated energies from the experimental energies is 0.28 MeV. From the values of these parameters, the energies and wave functions of about 50 levels are derived.

The wave functions are used to determine γ-ray branching ratios, mean lives, $ƒt$ values in allowed β-decay and spectroscopic factors for the ³⁷Cl(d, p)³⁸Cl reaction.

The computed branching ratios, mean lives and $ƒt$ values agree generally within a factor of 2.5 with the experimental values. Good agreement with experiment is obtained for the spectroscopic factors.

References (26)

F.C. Erné
Nucl. Phys.
(1966)
G.A.P. Engelbertink et al.
Nucl. Phys.
(1968)
P.W.M. Glaudemans et al.
Nucl. Phys.
(1967)
P.W.M. Glaudemans et al.
Nucl. Phys.
(1964)
P.W.M. Glaudemans et al.
Nucl. Phys.
(1964)
P.M. Endt et al.
Nucl. Phys.
(1967)
T.T.S. Kuo et al.
Nucl. Phys.
(1968)
F.C. Erné et al.
Nucl. Phys.
(1966)
B. Bošnjaković et al.
Nucl. Phys.
(1968)
K.P. Lieb
Nucl. Phys.
(1968)

J. van Klinken et al.

Nucl. Phys.

(1968)

J. Rapaport et al.

Nucl. Phys.

(1966)

R.D. Lawson

Nucl. Phys.

(1968)

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The nuclear-structure dependence of radiative corrections in superallowed Fermi beta-decay
1992, Nuclear Physics, Section A
We give a shell-model calculation of the nuclear-structure-dependent axial-vector contribution of the Born graphs to the radiative correction in superallowed Fermi β-decay. The impact of the correction is to give a modest improvement in the test of the conserved-vector-current (CVC) hypothesis, and a slightly smaller value of the quark-mixing matrix element, V_ud. The test of the unitary of the first row of the Kobayashi-Maskawa matrix gives: V_ud² + ν_us² + V_ub² = 0.9962 ± 0.0016, violating the three-generation standard model. Hints from neutron-only data suggest that nuclear-structure corrections in superallowed Fermi β-decay are still not fully under control.
Short lifetimes in 38Ar
1984, Nuclear Physics, Section A
Mean lifetimes of levels in ³⁸Ar have been measured using the Doppler-shift-attenuation (DSA) method and the reaction ³⁷Cl(p, γ)³⁸Ar. The lifetime values or limits were determined for 37 bound levels below the excitation energy of 9 MeV; the lifetimes of 9 levels, upper limits of 2 and lower limits of 3 levels are reported for the first time. For the effective stopping of recoils, the targets were prepared by implanting ³⁷Cl into Ta backings. The Monte Carlo method and the experimental stopping power were used in the DSA analysis.
Investigation of 1p-2h states in 39K with the 38Ar(3He, d)39K reaction
1974, Nuclear Physics, Section A
The 1p-2h aspect of ³⁹K states was examined by means of the ³⁸Ar(³He, d) reaction at $E(^{3} He) = 24 MeV$ . Angular distributions for 17 states up to an excitation energy of 7 MeV have been measured and analysed with DWBA calculations to determine the transferred angular momentum and spectroscopic factors. Almost the complete transition strengths have been observed for 1f_$72$ and 2p_$32$ states in ³⁹K with $T = 12$ . The isobaric analog state of the ³⁹Ar g state with $J^{π} = 72^{−}$ was found at an excitation energy of 6547 ± 15 keV. The spectroscopic results represent a sensitive test of shell-model wave functions calculated previously by several authors.
Investigation of 38Ar levels by 37Cl+p reactions. (II). Lifetimes, spins, parities and theory
1974, Nuclear Physics, Section A
The mean lives of 16 bound states of ³⁸Ar have been determined from DSA measurements at 14 selected ³⁷Cl(p, γ)³⁸ Ar resonances in the range E_p = 0.9–1.5 MeV. Spins and parities of 20 (p, γ) resonances have been determined from a precision comparison with corresponding ³⁷Cl(p, α₀)³⁴S resonances. Gamma-ray transition strengths combined with γ-ray angular distribution measurements at two resonances determine (or limit) the spins of 15 bound states of ³⁸Ar.
The experimental data on ³⁸Ar are compared with the results from shell-model calculations. The negative-parity states, especially those with high spin, can be very well described in terms of a model with five active nucleons in the 1d_$32$ shell and one in either the 1f_$72$ or 2p $32$ shell. For the positive-parity states, the new data underline the importance of two-particle four-hole excitations.
Investigation of 38Ar levels by 37Cl+p reactions. (I). Yield curves, excitation energies and branching ratios
1974, Nuclear Physics, Section A
Yield measurements have been performed on the reactions ³⁷Cl(p, p₀)³⁷Cl, ³⁷Cl(p, α₀)³⁴S (E_p = 1.17–1.70 MeV) and ³⁷Cl(p, n₀)³⁷Ar, ³⁷Cl(p.γ)³⁸Ar (E_p = 0.64–2.92 MeV); detailed investigations are restricted to resonances below E_p = 1.79 MeV. Resonance energies, strengths and (some) widths are reported for 12, 26 and 247 resonances in the reactions (p, p₀), (p, n₀) and (p, γ), respectively.
Simultaneous (p, α₀) and (p, γ) yield measurements over selected E_p intervals in the E_p = 0.88–1.64 MeV range established the existence of 42 resonances decaying by both γ and α₀ emission. Analysis of the γ-ray spectra of 100 ³⁷Cl(p, γ)³⁸Ar resonances leads to precision excitation energies (ΔE_x = 0.1–2 keV) of 57 bound states (E_x < 8 MeV) and branching ratios of the resonances and of 50 bound states.
Investigation of the reaction 37Cl(n, γ)38Cl
1973, Nuclear Physics, Section A
With Ge(Li) detectors the γ-radiation following thermal-neutron capture in natural and in ³⁷Cl enriched targets was studied. A total of 79 γ-lines has been assigned to the ³⁷Cl(n, γ) reaction and 64 of these lines have been placed in a decay scheme of ³⁸Cl. The excitation energies of 24 bound states of ³⁸Cl have been determined with 0.09–1.2 keV errors. The neutron separation energy of ³⁸Cl is 6107.7 ± 0.4 keV. A strong correlation between reduced stripping widths and (n, γ) primary reduced widths was found for the l_n(d, p) = 1 states if, instead of the Weisskopf reduction factor E_γ⁻³, a factor E_γ^−1.2 was used.

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^☆: This investigation was partly supported by the joint program of the “Stichting voor Fundamenteel Onderzoek der Materie” and the “Nederlandse Organisatie voor Zuiver Wetenschappelijk Onderzoek”.

^∗: The authors wish to thank Professor P.M. Endt for his stimulating interest in this work. The kind criticism of the manuscript by Dr. P.J. Brussaard is appreciated.

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Nuclear Physics A

Abstract

References (26)

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Cited by (44)

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Investigation of <sup>38</sup>Ar levels by <sup>37</sup>Cl+p reactions. (II). Lifetimes, spins, parities and theory

Investigation of <sup>38</sup>Ar levels by <sup>37</sup>Cl+p reactions. (I). Yield curves, excitation energies and branching ratios

Investigation of the reaction <sup>37</sup>Cl(n, γ)<sup>38</sup>Cl

Shell-model calculations on A = 38 nuclei☆

Abstract

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.