Early Signal of Emerging Nuclear Collectivity in Neutron-Rich ^{129}Sb

Radioactive ^{129}Sb, which can be treated as a proton plus semimagic ^{128}Sn core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, B(E2), for the 2^{+}⊗πg_{7/2} multiplet members and candidate πd_{5/2} state were measured. The results indicate that the total electric quadrupole strength of ^{129}Sb is a factor of 1.39(11) larger than the ^{128}Sn core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations performed with two different sets of nucleon-nucleon interactions suggest that this enhanced collectivity is due to constructive quadrupole coherence in the wave functions stemming from the proton-neutron residual interactions, where adding one nucleon to a core near a double-shell closure can have a pronounced effect. The enhanced electric quadrupole strength is an early signal of the emerging nuclear collectivity that becomes dominant away from the shell closure.

Electromagnetic Moments of Radioactive ^{136}Te and the Emergence of Collectivity 2p⊕2n Outside of Double-Magic ^{132}Sn

Radioactive ^{136}Te has two valence protons and two valence neutrons outside of the ^{132}Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon-nucleon interactions. Coulomb excitation of ^{136}Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0_{1}^{+}→2_{1}^{+}), Q(2_{1}^{+}), and g(2_{1}^{+}). The results indicate that the first-excited state, 2_{1}^{+}, composed of the simple 2p⊕2n system, is prolate deformed, and its wave function is dominated by excited valence neutron configurations, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2_{1}^{+}) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(2_{1}^{+}) was used to differentiate among several state-of-the-art theoretical calculations. Our results are best described by the most recent shell model calculations.

1p3/2 proton-hole state in 132Sn and the shell structure along N = 82

A low-lying state in 131In82, the one-proton hole nucleus with respect to double magic 132Sn, was observed by its γ decay to the Iπ=1/2- β-emitting isomer. We identify the new state at an excitation energy of Ex=1353  keV, which was populated both in the β decay of 131Cd83 and after β-delayed neutron emission from 132Cd84, as the previously unknown πp3/2 single-hole state with respect to the 132Sn core. Exploiting this crucial new experimental information, shell-model calculations were performed to study the structure of experimentally inaccessible N=82 isotones below 132Sn. The results evidence a surprising absence of proton subshell closures along the chain of N=82 isotones. The consequences of this finding for the evolution of the N=82 shell gap along the r-process path are discussed.

Coulomb excitation of radioactive 132,134,136Te beams and the low B(E2) of 136Te

The B(E2;0(+)-->2+) values for the first 2+ excited states of neutron-rich 132,134,136Te have been measured using Coulomb excitation of radioactive ion beams. The B(E2) values obtained for 132,134Te are in excellent agreement with expectations based on the systematics of heavy stable Te isotopes, while that for 136Te is unexpectedly small. These results are discussed in terms of proton-neutron configuration mixing and shell-model calculations using realistic effective interactions.

[A telemetric study of central rhythms in children]

Data concerning central (mu) rhythms in children are reported, these rhythms being studied by means of prolonged telemetric recording which makes it possible to study various experimental situations. Several different patterns of mu rhythm were observed in every subject, depending on the experimental situation. The level and the quality of attention on the one hand, immobility on the other, were found to be the two main factors which facilitated the occurrence or the maintenance of mu rhythms. The induction of movement, especially of the hand, was the major cause of blocking pre-existing mu rhythms, but attention alone was also able to provoke the same reaction. These data were compared with those obtained in animals by direct recording from the cortical somaesthetic areas. The respective roles of vigilance, attention and movement are discussed.