Identification of new excited levels in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>28</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>through the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:m

et al. 1995

Abstract. The systematics of 7-decay modes and radiative widths of highly excited states in 28Si has been extended by taking 7-ray spectra on 60 resonances of the 27Al(p, 7) reaction in the range 1097keV_< E,_< 4492keV (12643 keV _< Ex _< 15915 keV) and on the 24Mg(e,7) resonances at E~ = 3355, 3431, 4003 keV (Ex = 12860, 12925, 13415 keV). The y-decay modes of levels in the sub-resonance region (Ex = 10-12.5 MeV) were studied with both the 27Al(p, 7) reaction and the 27Al(d, nT) reaction at Ee = 4, 5, 6 MeV. Information on radiative widths of levels was obtained by measuring the resonance strengths S 7 = (2I + 1)FpF~fF for 52 resonances of the 27Al(p, 7) reaction with an emphasis on prospective T = 1 states.

Section: New Levels In 288i From the Zyal + P Reactionsmentioning

confidence: 98%

The structure of28Si above 10 MeV excitation energy I: gamma-decay modes and radiative widths of levels

et al. 1995

“…The observation of the 12 301keV level as a weak resonance in the 24Mg(~,7 ) reaction implies the presence of a small T = 0 component in its wave function which is not embarassing. 4 The study of two-particle transfer in the 26Mg(z, n) reaction [16] has yielded a U = 0 +, 1 + state at 12.27MeV excitation energy, which could be identical with the 12 301 keV level but also with a 12266keV level from the 27Al(d, n) reaction [25], whose quantum numbers are as yet uninvestigated.…”

Section: Isotopic Spin Assignmentsmentioning

confidence: 98%

The structure of28Si above 10 MeV excitation energy II: Assignments of quantum numbers

et al. 1995

Abstract. New assignments of quantum numbers have been obtained for more than 50 levels in 2ssi between 8953 and 15915 keV excitation energy. They are based on the measurement of 7-ray angular distributions or anisotropics on 29 resonances of the 27Al(p,7) reaction and on the 24Mg(c~,7) resonance at E~ = 3355keV. A total of 15 high-spin states with I = 5-7 has been obtained and the spectrum of T = 1 states has been identified up to 15 915 keV excitation energy and a maximum spin I=6.

“…These facts raise the suspicion that we have here a series of intruder states which form a K ~ = 0 + rotational band. The I ~ = 0 + bandhead must then be sought in the as yet unconsidered 8819 keV level, which has been observed in the 2:Al(d, n) reaction [17] and which is also visible, though only weakly, in a published spectrum [271 of the 27Al(T, d) reaction. There is no chance of observing the 4 § --* 2 + and 2 + --, 0 § "inband transitions" because they are hindered by a low transition energy.…”

Section: Intruder States and Unconsidered Statesmentioning

confidence: 99%

“…Only 16 out to 246 levels most of them above 13.4 MeV excitation energy, remain uninvestigated. Most of these have been observed in the ZTAl(d, n) reaction only [17] and their existence has been considered as dubious in the 1990 compilation. Above 14.53 MeV excitation energy our knowledge of the 2sSi level scheme as given in Table 1 is no longer complete, but several interesting levels, most of them with a tentative T = 1 assignment have been observed [11].…”

Section: Introductionmentioning

confidence: 96%

“…An asterisk is indicative of excitation energies obtained (with keV accuracy) in a preceding paper [10]. Errors are given only if:they exceed 1 keV b Quantum numbers without reference have been obtained from the compilation of [12] for E~ < 14 MeV and from [13] for higher energies ~ h Quantum numbers and/or excitation energies adopted from c [14], a [15], ~ [17], ~ [18], g [19], h [12] i From 7,decay modes of [10] k From Table 4 of [11] 1From Table 2 of [11] reAssignments of J, 7z, T from Table 5 of [11] "The T-assignment is obtained :in Table 5 of [11] ~ I = = 0 +, 1 + assignment which is based on an observed L = 0 transfer in the 26Mg(~', n) reaction [20] should not be taken for granted since the transfer could lead to the 12 301 keV level…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The structure of28Si above 10 MeV excitation energy III: Level scheme and shell model interpretation

et al. 1995

Abstract. The 2*Si level scheme up to 14.5 MeV excitation energy is reevaluated using information from two preceding papers. It consists of approximately 250 levels which are almost completely characterized according to the quantum numbers 1, re, T of the levels. The properties of positive-parity states are compared to the predictions of shell model calculations within the complete s-d basis space using the unified s-d shell Hamiltonian. A spectrum of 48 experimental T = 1 states between 9.3 and 16 MeV is reproduced with a rms deviation of only 150 keV. A calculation of radiative widths and 7-decay modes which uses free-nucleon 9-factors yields excellent agreement with experiment and confirms that quenching of M1 transitions is only marginal in 2ssi. The detailed shell model analysis of the T = 0 spectrum is extended to the limiting energy where T = 1 wave function admixtures, not contained in the theory, become important experimentally. This happens at 6-8 MeV above the yrast state, depending on the spin value. Altogether it appears that a spectrum of 171 levels below 14.5 MeV, which have positive or unassigned parity, is almost completely accounted for by the model. Apparent intruder states from outside the s-d shell space are observed at Ex=lO945keV (U=4 +) and 12860 keV (U= 6 +) and are interpreted as members of a K S = 0 + rotational band.