Springer Online Journal Archives 1860-2000
Abstract Theγ-decay of levels in21Ne up to 10 MeV excitation energy has been investigated byn — γ coincidence measurements initiated with the18O(α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining then — γ angular correlation measurements performed atE α=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleus21Na. The resulting values of Ex[keV]−J π are as follows: 4525-5+, 4686-3+, 5431-7+, 5549-3+, 5819-7−, 6175-7+, 6268-9+, 6550-9, 6639-9, 7006-7+, 7041-9, 7356-7 or 9, 7422-11(−), 7648-7+, 7981-11 or (7+), 8154-9, 8240-11, 8664-9− or 11 or 13−, 9401-13−, 9867-13− or 15+, 9941-13− or 15 or 17+. The assignment of mirror levels in21Ne —21Na has been extended to the 6175 keV level of21Ne. Excitation energies, electromagnetic properties, Gamow−Teller matrix elements and spectroscopic factors of positive parity states are compared with the results of shell-model calculations which employ a unifieds—d shell Hamiltonian and the unrestricted configuration space of the 0d 5/2 —1s 1/2—0d3/2 shell. Collective properties contained in shell model wave functions are explored up to the termination of bands atJ=17/2 or 19/2. The spectrum of intruder states in21Ne is observed to begin with a 5628 keV,J π=7/2+ state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands.
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