Multiple coulomb excitation of202Hg and204Hg

Abstract

Multiple Coulomb excitation measurements on z~176have been performed with 5 MeV/u 2~ projectiles. The ground bands are excited up to the newly discovered 6 + states and B(E2) values are derived for the 4 + -->2 + and 6 + --+4 + transitions. Whereas the 2 + and 4 + levels in the Hg isotopes with 196_<A<204 have an almost constant energy, the 6 + levels increase in 2~and 2~ compared to the lighter isotopes, by approximately 100 and 300 keV, respectively. The relative B(E2) values in both nuclei show that the collectivity in the neutron rich Hg nuclei is of more complex origin than expected from the few proton and neutron holes with respect to the 82 and 126 major shells.

Isotope shift of182Hg and an update of nuclear moments and charge radii in the isotope range181Hg-206Hg

“…Unfortunately no fi3 values for other mercury isotopes have been measured. Re-cent multiple Coulomb excitation measurements on 2~176 [62] have shown that the collectivity in the neutron rich Hg nuclei is of more complex origin than expected from the few proton and neutron holes with respect to the Z = 82 and N = 126 major shells.…”

Investigation of196,198Pt and202,204Hg with the (d, pn?) reaction

“…The positive parity levels in 2~ and 2~ can be compared with theoretical predictions of the particle-vibration coupling model [32] and the interacting boson model [-33]. A discussion of the ground bands is given in [1] where it is concluded that these levels show an unusually large collectivity, which can not be fully explained by the two models. In 2~ three additional low lying levels are observed with I~--2 +, 2 +, and 4 +.…”

“…ions [1]. A study of 7-rays in the deuteron break-up reaction seemed promising for an investigation of levels with moderately high spins, since this method has been successfully used in the uranium region [2].…”

Identification of the one-quadrupole phonon 21,ms+ state of 204Hg

“…This spectrum is dominated by the 437-keV, 2 + 1 → 0 + , transition of 204 Hg with 9.5 × 10 7 counts. All other strong γ rays originate from 204 Hg excited states [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] as well and most of these are in coincidence with the ground-state transition (cf. Fig.…”

“…The high detection efficiency of Gammasphere permits measurements of angular distributions for sufficiently intense transitions, allowing to extract the A 2 /A 0 and A 4 /A 0 coefficients given in [31]) of the 4 + 1 state which may lead to a substantial attenuation of the anisotropy when excited 204 Hg nuclei recoil in vacuum [44]. This effect is even more pronounced for the 2 + 1 → 0 + transition -its detected angular distribution is isotropic (cf.…”