Identification of the6+and8+Yrast States in

Abstract

The reaction 28 Si( 14 N,/my) 40 Ca has been used to populate high-spin states in 40 Ca, and levels at 6930 and 8098 keV are identified as the 6 + and 8 + yrast states. The results suggest the termination at spin 8 of the band based on the 3.35-MeV state. The previously identified level at 6930 keV is found to be a doublet.The softness of the doubly magic 40 Ca nucleus to particle-hole excitations has been used to explain the nature of the first excited 0 + state at 3.35 MeV, which is interpreted as the lowest member of a 4p-4h (four particle, four hole) prolate rotational band. 1 The experimental evidence for such a band is primarily the energies of the lowest 2 + and 4 + states, which fit reasonably well a J(J + 1) spacing from the excited 0 + state, and the enhanced E2 transitions between these states. 2 It is of crucial importance for the understanding of the 40 Ca spectrum and hence of other/-/)-shell nuclei to test this interpretation by locating the higher-spin members of this band. We have located two states which we suggest are the 6 + and 8 + yrast states. The location of the proposed 8 + state and the small E2 enhancement of its decay to the proposed 6 + state indicate that the rotational model ceases to be applicable at spin 8.The "grazing-collision" picture of Klapdor et at. 3 suggested that 28 Si( 14 N, pny) 40 C2L at an incident laboratory energy of 30-40 MeV would feed highspin states in 40 Ca. The experimental procedures were similar to those used in other heavy-ion reactions in this mass region, 4 " 6 We have measured y-ray excitation functions and y-ray angular distributions (which also permit observation of Doppler shifts). To identify 40 Cay rays, ayy coincidence experiment was performed with a 35-MeV 14 N beam incident on a silicon chip. Ad-200 100 0 200| IOO o: M^dhAtiMMt^iMi \mi)kxMUt GATE-1169 (8 + -6 + ) J*kmJi& MH,,^M*mUM-.,

Superdeformation in the Doubly Magic NucleusC2040a20

“…Their contributions were subtracted to obtain a clean data set for 40 Ca. Some of the high-spin structures in 40 Ca have previously been studied [13,14]up to spin 8 1 at 8.1 MeV. An interesting feature of the previous level schemes is the presence of second 0 1 2 and third 0 1 3 states, which are indications of shape coexistence [7].…”

Deformed states of high spin in42Ca

“…8+~6 + transition. Simpson et al [6] interpret this phenomenon as a termination of the rotational band, which could be explained if the microscopic description involved 2 p -2 h rather than 4 p -4 h excitations. On the other hand the smooth change of parameters of the rotational band from 3BAr to 42Ca suggests, that the 4~ band should behave regularly.…”