Lifetimes of 2+ and 4+ rotational states in heavy doubly even nuclei

Ton, H.; Beens, W. W.; Roodbergen, S.; Blök, J.

doi:10.1016/0375-9474(70)90088-6

Cited by 50 publications

(3 citation statements)

References 18 publications

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“…The lifetimes of the first J π = 2 + and 4 + states have previously been measured using the delayed-coincidence technique, where the difference in time between detection of a populating α particle and the de-exciting γ-ray was measured [27]. Our results are in good agreement with these studies confirming a large quadrupole deformation in the ground state.…”

Section: Measurement Of the Lifetimes Of Excited States Of 228 Thsupporting

confidence: 86%

First direct measurement of the intrinsic dipole moment in pear-shaped thorium isotopes

Chishti,

O'Donnell,

Battaglia

et al. 2019

Preprint

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It is now well established that atomic nuclei composed of certain combinations of protons and neutrons can adopt reflection-asymmetric, or octupole-deformed, shapes at low excitation energy. These nuclei show promise in the search for a permanent atomic electric dipole moment, the existence of which has implications for physics beyond the Standard Model. Theoretical studies have suggested that certain isotopes of thorium may have the largest octupole deformation. However, due to experimental challenges, the extent of the octupole collectivity in the low-energy states in these thorium nuclei has not yet been demonstrated. This paper reports measurements of the lifetimes of low-energy states in 228 Th (Z = 90) undertaken using the mirror symmetric centroid difference method, which is a direct electronic fast-timing technique. Lifetime measurements of the low-lying J π = 1 − and 3 − states, which are the first for a thorium isotope, have allowed the B(E1) rates and the intrinsic dipole moment to be determined. The results are in agreement with those of previous theoretical calculations allowing the extent of the octupole deformation of 228 Th to be estimated. This study indicates that the nuclei 229 Th and 229 Pa (Z = 91) may be good candidates for the search for a permanent atomic electric dipole moment.

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Section: Measurement Of the Lifetimes Of Excited States Of 228 Thsupporting

confidence: 86%

First direct measurement of the intrinsic dipole moment in pear-shaped thorium isotopes

Chishti,

O'Donnell,

Battaglia

et al. 2019

Preprint

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“…However, decay spectroscopy combined with fast electron detection (using a plastic scintillator) allows high-precision lifetime measurements in actinides. This technique was used almost 50 years ago to measure the 2 + lifetimes in 228 Th, 234,236 U, 238,240 Pu and 248 Cm [323]. In the last nucleus, the measured value t 120 10 1 2 =  ps still represents the only direct measurement; the adopted value 122.5 ± 2.5 ps [324] actually results from analysis of Coulex data and is therefore deduced from the measured B E2 ( ).…”

Section: Global Properties Of Rotational Bandsmentioning

confidence: 99%

“…Besides energies of γ-ray transitions, the reduced transition probabilities B E2 ( ) were also deduced up to I 22 = . The fit procedure included the lifetime of the 2 + state measured by Ton et al [323]. No similar measurement could be yet performed for the heaviest nuclei.…”

Section: Global Properties Of Rotational Bandsmentioning

confidence: 99%

Nuclear structure features of very heavy and superheavy nuclei—tracing quantum mechanics towards the ‘island of stability’

Ackermann

Theisen

2017

Phys. Scr.

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The quantum-mechanic nature of nuclear matter is at the origin of the vision of a region of enhanced stability at the upper right end of the chart of nuclei, the so-called ‘island of stability’. Since the 1960s in the early second half of the last century, various models predict closed shells for proton numbers 114–126 and neutron numbers such as 172 or 184. Being stabilized by quantum-mechanic effects only, those extremely heavy man-made nuclear species are an ideal laboratory to study the origin of the strong nuclear interaction which is the driving force for matter properties in many fields ranging from microscopic scales like hadronic systems to cosmic scales in stellar environments like neutron stars. Since the 1950s, experiments on the synthesis of new elements and isotopes have also revealed various exciting nuclear structure features. The contribution of Bohr, Mottelson and Rainwater with, in particular, the development of the unified model played an essential role in this context. Although not anticipated in the region of the heaviest nuclei, many phenomena were subsequently discovered like the interplay of collective features manifesting themselves e.g. in nuclear deformation, ranging from spherical to prolate and oblate shapes with the possible occurrence of triaxial symmetries, and single particle states and their excitation into quasiparticle configurations. The continuous development of modern experimental techniques employing advanced detection set-ups was essential to reveal these exciting nuclear structure aspects in the actinide and transactinide regions since the production cross-section becomes extremely small with increasing mass and charge. Further technological progress, in particular, high intensity stable ion beam accelerator facilities presently under construction, as well as potentially in the farther future radioactive neutron rich ion beams provide a high discovery potential for the basic understanding of nuclear matter.

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Nuclear data sheets for A = 215,219,223,227

Browne

1992

Nuclear Data Sheets

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Lifetimes of 2+ and 4+ rotational states in heavy doubly even nuclei

Cited by 50 publications

References 18 publications

First direct measurement of the intrinsic dipole moment in pear-shaped thorium isotopes

First direct measurement of the intrinsic dipole moment in pear-shaped thorium isotopes

Nuclear structure features of very heavy and superheavy nuclei—tracing quantum mechanics towards the ‘island of stability’

Nuclear data sheets for A = 215,219,223,227

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