New ß-decaying state in 214Bi

A new β-decaying state in 214Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred Iπ = (8−) assignment was suggested for this state based on the β-decay feeding pattern to levels in 214Po and shell-model calculations. The half-life of the Iπ = (8−) state was deduced to be T1/2 = 9.39(10) min. The deexcitation of the levels populated in 214Po by the β decay of this state was investigated via γ -γ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in 214Bi and 214Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new β-decaying state as an Iπ = 8− isomer and allow for tentative assignment of shell-model states to several high-spin states in 214Po.peerReviewe

New ß-decaying state in 214Bi

A new β-decaying state in 214Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred Iπ = (8−) assignment was suggested for this state based on the β-decay feeding pattern to levels in 214Po and shell-model calculations. The half-life of the Iπ = (8−) state was deduced to be T1/2 = 9.39(10) min. The deexcitation of the levels populated in 214Po by the β decay of this state was investigated via γ -γ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in 214Bi and 214Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new β-decaying state as an Iπ = 8− isomer and allow for tentative assignment of shell-model states to several high-spin states in 214Po.peerReviewe

Pairing and vibrational correlations in the higher Tamm-Dancoff approximation (HTDA) approach

The higher Tamm-Dancoff Approximation (HTDA) is extended to include vibrational correlations with or without pairing correlations. The residual interaction in use is of the delta (in the T = 1 channel) plus multipolemultipole type. In this paper we have limited our study to the mere case of isoscalar quadrupole correlations. The approach is illustrated by the consideration of ground state and isoscalar giant quadrupole resonance properties in the 40Ca nucleus

THE HIGHER TAMM–DANCOFF APPROXIMATION: THEORETICAL CONTEXT AND PHENOMENOLOGICAL ASPECTS

We present the key aspects of the theoretical foundations of the Higher Tamm–Dancoff Approximation which can be interpreted as a truncated shell-model approach based on a Hartree–Fock solution, ensuring the conservation of the particle number. Then we discuss some phenomenological aspects of the residual interactions used, namely the delta interaction to describe the neutron–neutron and proton–proton pairing correlations and the quadrupole–quadrupole interaction to describe vibrational correlations

Lifetime measurements in the yrast band of Po-212 with a shell-model investigation

The lifetimes of the first excited 4(+) and 6(+ )states in Po-212 were measured using the recoil-distance Doppler shift method. The nucleus of interest was populated in the Pb-208(O-18, C-14)Po- 212 reaction. The experimental results are compared to large-scale shell model calculations performed using the recently developed H208 effective interaction. The calculations describe well the low-lying structure of( 212)Po with an exception of the 2(1)(+) -> 0(1 )(+)transition rate which is strongly overestimated. This has been attributed to additional components in the wave function of the ground state

Proton-Neutron Pairing Correlations in the Self-Conjugate Nucleus K-38 Probed via a Direct Measurement of the Isomer Shift

A marked difference in the nuclear charge radius was observed between the I/pi = 3+ ground state and the I/pi = 0+ isomer of 38K and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of (r_c^2)(38Km)-(r_c^2)(38Kg)=0.100(6)fm^2 was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in 38K have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the N, Z=20 shell gaps, confirming the significance of cross-shell correlations in the region of 40Ca.status: publishe