Nuclear Structure of Na22.I. Gamma-Ray Correlations and Lifetime Measurements for Levels of Eex<3.1 MeV

E. K. Warburton, J. W. Olness, and A. R. Poletti
Phys. Rev. 160, 938 – Published 20 August 1967
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Abstract

Levels of Na22 below an excitation energy of 3.1 MeV have been investigated through the F19(α, nγ)Na22 and Ne20(He3, pγ)Na22 reactions. Gamma-ray spectra from the first reaction were recorded with an 8-cc Ge(Li) detector at 90°, 0°, and 166° to the α beam using CaF2 targets and α energies between 4.0 and 7.0 MeV. Spectra were similarly recorded at 90° for EHe3=5.65 MeV in the second reaction. These studies were supplemented by γγ coincidence measurements with both NaI(Tl)-NaI(Tl) and NaI(Tl)-Ge(Li) γ-ray detector combinations. Gamma-ray angular distributions were measured at Eα=5.48 MeV using the F19(α, n)Na22 reaction and pγ angular correlations were measured at EHe3=5.65 MeV using the Ne20(He3, p)Na22 reaction. From these measurements excitation energies and γ-ray decay modes were determined for the levels below 3.1-MeV excitation, information on spin-parity and isotopic-spin assignments was obtained, and values or limits for the mean lifetimes of the levels were extracted from observations of the γ-ray Doppler shifts. An isotopic-spin assignment of T=1 was made to the Na22 1.952-MeV level; all other levels in the range 0.7<Ex(MeV)<3.1 were assigned T=0. Upon combining our results with previously available information, we deduce the following spin-parity and lifetime information {Eex(MeV)[Jπ; τm(psec)]} for the third through eleventh levels of Na22: 0.891 (4+; >8), 1.528 (3+, 5+; 3.8±0.9), 1.937 (1+; <0.06), 1.952 (1, 2; <0.09), 1.984 (2+, 3+; 1.6±0.34), 2.211 (1; >11), 2.572 (≤3; >10), 2.969 (≤3; <0.14), 3.059 (≤3; <0.09). The combined influence of Doppler effects and the lifetimes of the initial states on the shapes of the full-energy-loss peaks of the 1.528 → 0 and 1.984 → 0.583 transitions is quite marked. The analysis of these shapes to obtain the lifetimes given above is described in detail. Some incidental information concerning excitation energies and lifetimes of energy levels in F19 and Ne22 is given in an Appendix.

  • Received 17 March 1967

DOI:https://doi.org/10.1103/PhysRev.160.938

©1967 American Physical Society

Authors & Affiliations

E. K. Warburton, J. W. Olness, and A. R. Poletti

  • Brookhaven National Laboratory, Upton, New York

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Issue

Vol. 160, Iss. 4 — August 1967

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