Search

The γ-decay of levels inNe up to 10 MeV excitation energy has been investigated by n - γ coincidence measurements initiated with theO( α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining the n - γ angular correlation measurements performed at E=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleusNa. The resulting values of E[keV]− J 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 inNe -Na has been extended to the 6175 keV level ofNe. 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 unified s-d shell Hamiltonian and the unrestricted configuration space of the 0 d -1 s-0d shell. Collective properties contained in shell model wave functions are explored up to the termination of bands at J=17/2 or 19/2. The spectrum of intruder states inNe is observed to begin with a 5628 keV, J=7/2 state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands. [ABSTRACT FROM AUTHOR]

Particle γ-ray coincidences have been measured in theSi ( d,pγ) reaction at 6.5 and 7 MeV bombarding energy, in theMg ( α,nγ) reaction at 12, 14 and 15 MeV, and in theA1 ( τ,pγ) reaction at 9 MeV. The γ-decay has been observed for all bound states ofSi and for 56 unbound states up to 12,960 KeV excitation energy. Particle γ-ray angular correlations were measured in theSi ( d,pγ) reaction at 6.5 MeV and in theMg ( α,nγ) reaction at 12 MeV. Spin (-parity) assignments or restrictions were obtained for nearly all bound states and some high-spin states above the binding energy. The assignment of mirror levels inSi andP has been extended to 8.2 MeV excitation energy. The excitation energies of 41 positive-parity states are reproduced by shell model calculations. The possible existence of a K=5/2 band with prolate deformation is discussed. [ABSTRACT FROM AUTHOR]

A search for high-spin states inSi has been performed by n−y coincidence measurements in theMg( α, nγy) reaction at E=14 and 15.5 MeV. Spin-parity assignments of the observed levels were obtained from n−γ angular correlation and lifetime measurements at E=14.5 MeV. The γ-decay of the 9,164 keV level was investigated separately with theAl( p, γ) reaction at the E=2,160 and 2,312 keV resonances. Rotational bands with K=3 (comprising levels at E=6,879, 8,413, 10,188 and 12,204 keV), K =5 (comprising levels at E=9,702, 11,577 and 13,741 keV) and K=0 (comprising levels at E=6,691, 7,381, 9,164 and 11,509 keV) were observed. The finding of the latter band supports the idea of coexisting oblate and prolate shapes inSi. A level at 14,643 keV excitation energy has the properties of the I=8 member of the ground state band. There are additional positive-parity high-spin states which do not fit into rotational bands. All types of positive-parity states are well accounted for by shell model calculations. [ABSTRACT FROM AUTHOR]

Highly excited states inSi were investigated using theAl( α, p γ) reaction. Proton- γ ray angular correlations were measured at E=12, 14.1 and 15MeV. At 15MeV linear polarizations of γ-rays were measured in coincidence with protons using a five-crystal Compton-polarimeter. Lifetimes were measured at E=14.6 MeV using the Dopper-shift attenuation method. Unambigious spin-parity assignments were obtained for the levels at 6,865 (3), 7,001 (5), 7,079 (3), 7,810 (4), 9,371 (6), 7,613 (4), 8,196 (5), 8,596 (4), 8,963 (5), 9,111 (6), 9,350 (4), 9,507 (5), 9,777 (6), 10,188 (5), 10,305 (3), 10,561 (6), 10,725 (7), 11,477 (6) and 11,544 (7)keV excitation energy, respectively. The structure ofSi is understood both in terms of the shell model and the collective model. The levels at 5,487, 6,505, 8,196, 9,777 and 11,544keV, respectively, are the I=3 through 7 members of a well developed K=3 rotational band with intrinsic quadrupole moment | Q|=350mb. There is evidence of further rotational bands, among them a K=3 band with | Q|=800 mb. [ABSTRACT FROM AUTHOR]

The γ-decay modes ofAr levels with E≦11,630keV and ofCa levels with E≦10,036keV have been studied using theCl( α, pγ) reaction at 16MeV and theK( α, pγ) reaction at 15.14 MeV, respectively. In both nuclei the number of states with J≧6 exceeds fifty. Weak coupling calculations of the Bansal and French type reproduce the density of high-spin states. The success of the model implies that the excitations of up to four particles from the d into the f shell play a role in both nuclei. The structure of deformed states was found to be predominantly 4 p/s 6 h inAr and 4 p/s 2 h inCa, respectively. [ABSTRACT FROM AUTHOR]

TheSc( α, p γ) reaction has been investigated at E=11, 12 and 13MeV. The γ-decay of 198 levels inTi up to 8,323 keV excitation energy has been observed. High-spin states were investigated by proton- γ ray angular correlation measurements at E=11 and 13MeV and by DSAM lifetime measurements at E=11 MeV. From the combined evidence spin (-parity) assignments were obtained for the levels at E=8,323 keV ( J= 10,8,6), 8,091(12, 10, 8, 6), 7,668(10, 8), 7,427(9, 7), 7,374(11, 9, 7), 6,906(10, 8, 6), 6,172(8,6), 6,102(10,8), 6,039(6), 6,034(9, 7), 5,630(7), 5,197(8), 5,169(7), 5,155(5), 4,404(5), 4,398(6) and 4,046keV (5). Most of the ambiguous spin assignments become unique if the 8,091 keV level has J=12, an assumption which is favoured by its excitation function. The level spectrum thus obtained is well reproduced by shell model calculations in the pure ( f) configuration space. Discrepancies exist in the reproduction of γ-decay modes. The reason is found in low-lying high-spin intruder states which include the 7,427 and 8,323 keV levels. The spectrum of negative-parity states is understood qualitatively by a comparison withTi andCa. [ABSTRACT FROM AUTHOR]

The excited states ofMg have been investigated up to E=7976 keV using theMg( d, pγ) reaction. A measurement of proton- γ-ray angular correlations at E=6.5 MeV has yielded spin-parity assignments or restrictions of levels up to E=6508 keV and accurate excitation energies and branching ratios of levels up to E=7976keV, respectively. The Doppler-shift attenuation of γ-rays has been measured at E==5.5 MeV yielding information on the lifetimes of levels up to E=6009keV. The properties of positive-parity levels up to E=5 MeV are successfully reproduced by recent shell-model calculations. The rotational model is also applicable to the description of collective properties without reaching the overall agreement of the shell model. The negative-parity states are well described by the rotational model. [ABSTRACT FROM AUTHOR]

The γ-decay of 93Ar levels between 6.84 and 10 MeV excitation energy has been measured using theCl(α, pγ) reaction at E=14 MeV. A previous measurement of the same reaction could be exploited in the light of the present results, yielding spin(-parity) assignments J(7,070)=5, J(7,507)=7,5, J(8,077)=7, J(8,129)=5,6 and J(8,488)=7,5. The γ-decay modes of yrast levels, which have been previously observed in heavy ion induced reactions, are revised leading to major changes in their spin-parity assignments. New candidates for the J=8 and 9 levels were found in the levels at 9,644 and 9,928 keV excitation energy, respectively. A comparison of yrast levels with shell-model calculations is satisfying. [ABSTRACT FROM AUTHOR]

TheCa levels at 4,715 and 6,633 keV excitation energy have been investigated using the K(α,pγ reaction at E=14 and 15 MeV. From particle- γ-ray angular correlations the spin assignments J(4,715)=6, 4 and J(6,633)=8, 6, 4 have been obtained. Lifetime measurements using the Doppler-shift attenuation method yielded τ (4,715)=120±46 fs and τ(6,633)=52±21 fs. Both levels have positive parity and decay by enhanced E2 transitions. They are interpreted as the J=6 and 8 members, respectively, of the K=0 rotational band which has the E=1,837, 2,423 and 3,250 keV states as further members. The enhancement of inband E2 transitions is 50W.u. (6→4) and 63 W.u. (8→6) respectively. The intrinsic quadrupole moments which have been derived on the basis of the coexistence model, are Q=1.13−0.16/+0.37 b(8→6) and Q=1.36±0.25 b(6→4), respectively. The J=10 member of the rotational band has possibly been observed as a level at 8,856±5 keV excitation energy. [ABSTRACT FROM AUTHOR]

TheMg(α, nγ) reaction has been used in connection with a neutron time-of-flight spectrometer to search for high spin states inSi between E=8.4 and 11.4 MeV. The γ-decay of twenty levels has been observed. Nine levels have not been observed before. A candidate for the J=13/2, K=7/2 state has been located with the E=8761 keV level. [ABSTRACT FROM AUTHOR]