Quadrupole moments of high spin isomers inFr213,Fr

Abstract

The level mixing spectroscopy method has been applied to measure the static quadrupole moments of six isomeric states in "Fr, " Fr, and "Fr (Z = 87). For isomers with the proton configuration mh 9/2l13/2 a large increase of the quadrupole moment was observed with the removal of neutrons from the closed %=126 core: Q( -+, ' Fr)= -70 (7) e fm, Q(15, ' Fr)= -80(12) e fm', and Q ( -',9, 2 "Fr) = -107(18) e fm'. Quadrupole moments for very high spin states were also measured: Q( -, ',' "Fr)= -219(53) e fm', Q(27, '"Fr)= -152(31) e fm, and Q( -, ',"' Fr)= -198(56) e fm . The observed values are in good agreement with shell-model calculations, but are lower than that predicted using the deformed-independent particle model. The implantation behavior of Fr in a Tl host is also discussed.

Review of metastable states in heavy nuclei

“…Its magnitude can be explained by the mixed shell-model configurations, without requiring significant deformation [203]. A similar conclusion was reached [205,206] from the measurement of the quadrupole moments in the francium isotopes, which have related configurations, although, in contrast, general agreement is obtained with MOPC shell-model calculations. The theoretical analysis of Sagawa and Arima [212], for a number of high-spin isomers in the lead region, also concurs.…”

“…The 30 + →27 − decay is similar, with two interfering components. A similar scenario applies to the decay of numerous high-spin isomers with related configurations that have been discovered in this region, including the astatine isotopes [151,169,201,202], other radon isotopes [203,204] and the francium isotopes [205,206,207]. 212 Rn The DIPM calculations of Andersson et al [139] used the Strutinsky method and the modified harmonic oscillator potential to predict states (specifically yrast traps) up to 30 in 212 Rn.…”

“…Considering the four two-valenceparticle and hole nuclei in which the high-spin j 2 isomers are expected, 206 Hg, 206 Pb, 210 Pb and 210 Po, the two-proton-hole case, 206 Hg, was the only one for which such experimental information was missing, largely because of the absence of experimental techniques to populate high-spin states in neutron-rich nuclei. Observation of the 10 + , 92(8) ns isomer [184] then gave an effective charge of 1.60(7) for the h 11/2 protonhole orbital.…”

“…The two-proton-hole, two-neutron-hole nucleus 204 Hg [186], includes a proposed J π = 22 + isomer at 7226 keV obtained from the maximum alignment of the high-spin proton and neutron holes, πh 11/2 , J π = 10 + state is found at 3723 keV in 206 Hg. Combining the experimental energies of these two states and allowing for the residual interaction of −543 keV predicted for the fully aligned coupling, leads to an expected energy of 4027 + 3723 − 543 = 7207 keV, very close to both the observed state and the shell-model calculation (which effectively incorporates the same interactions).…”

LEMS: application of the method to study the static quadrupole moment of the isomer in 179W

“…The method of the level mixing spectroscopy (LEMS) [1] has proven to be a powerful tool to study the quadrupole interaction of a nuclear isomeric state with the electric field gradient (EFG) of a host material, especially at high spin. Recently the quadrupole moments of a number of high-spin isomers have been determined in the lead region [2,3,4].The LEMS method can be explained as follows: an aligned ensemble of highly excited nuclei is produced in a heavy-ion fusion-evaporation reaction. The reaction products recoil into a host material.…”