<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>Decay of Deformed Actinide Nuclei

Stewart, Timothy L.; Kermode, M W; Beachey, D; Rowley, N.; Grant, I. S.; Kruppa, A. T.

doi:10.1103/physrevlett.77.36

Cited by 40 publications

(34 citation statements)

References 15 publications

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“…Hereby, all four possible choices for the relative phases between the partial a waves are considered. For one choice ͓sgn͑a 0 , a 2 , a 4 ͒ ͑1, 2, 2͔͒ the formation amplitudes turn out to be rather constant for a wide range of actinide nuclei [22]. Moreover, the a 2 amplitudes are negative for this solution.…”

Section: Nucleusmentioning

confidence: 98%

“…Large prolate deformations, however, cause sufficient mixing between the different L waves to induce preferential emission along the symmetry axis. Using the values thus derived, the a anisotropies of various odd-A nuclei are computed [22]. It should be noted that in contrast with the work of Delion et al, Stewart et al assume that no mixing of the daughter states occurs in the decay.…”

Section: Nucleusmentioning

confidence: 99%

“…In Ref. [22] no prediction for 229 Pa was given. The reason for the difference between experiment and theory is not very clear.…”

Section: Nucleusmentioning

confidence: 99%

“…[20] Table II. Stewart et al [22] also use Fröman's method [5], but use a realistic nuclear potential to calculate the tunneling probability of the a particle through the deformed barrier, including b 2 and b 4 deformations. The formation amplitudes a L of the partial a waves with angular momentum L at the nuclear surface, however, are extracted from the fine structure in the a decay of neighboring even-even nuclei.…”

Section: Nucleusmentioning

confidence: 99%

“…Systematic uncertainties in the derivation of the f parameter used in the evaluation for each isotope are included in the uncertainties given in Table I. [19][20][21], by Stewart et al [22], and by Berggren [23]. In their "tunneling" model, the former have adopted the same approach as in older work [3][4][5] but employed a much larger shell model configuration space to compute the formation probabilities and also included possible octupole deformation in the determination of the tunneling factors.…”

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confidence: 99%

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Angular Distributions ofαParticles Emitted by Deformed Oriented Nuclei

et al. 1999

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A detailed quantitative experimental investigation of the influence of nuclear deformation on the angular distribution of a particles emitted by oriented nuclei is reported. The favored a transitions in the decay of the deformed nuclei 221 Fr, 227 Pa, and 229 Pa were studied. In all three cases, very large anisotropies have been observed. The results are in good agreement with calculations based on a particle tunneling through a deformed Coulomb barrier. [S0031-9007(99) Alpha decay is a textbook example of quantum mechanical tunneling of a particle through a potential barrier. The exponential energy dependence of the a decay rate is indeed well explained by the tunneling of a preformed a particle through the Coulomb barrier of atomic nuclei [1]. Hill and Wheeler [2] argued that in a nucleus with a deformed Coulomb barrier the tunneling probability becomes direction dependent, resulting in anisotropic a emission from an ensemble of oriented nuclei (i.e., nuclei with a preferential spin direction in space). A firmer theoretical framework was built later [3][4][5][6], in which the shell model-including Bardeen-Cooper-Schriefer pairing [7]-was used to compute the formation amplitude of the a particle at the nuclear surface while employing the Wentzel-Kramers-Brillouin approximation [8] to calculate tunneling through the (deformed) Coulomb barrier.Based on the works mentioned above, the observation of anisotropic a emission from heavy nuclei has often been attributed to the tunneling of the a particles through a deformed barrier, thus relating a anisotropies to nuclear deformation [9]. This relationship, however, has not been firmly established experimentally. Indeed, the only a anisotropy experiments on nuclei known to be deformed were performed on prolate actinide nuclei more than two decades ago [10]. As predicted, a preferential emission of the a particles along the nuclear symmetry axis was observed. However, at that time, the source preparation technique and the quality of the detectors available did not allow resolution of the different a transitions in the decays investigated and no detailed conclusions could be drawn. These problems were solved for the first time when high-resolution particle detectors operating near 4.2 K were linked with ion implantation techniques for sample preparation [11]. Using this combination we have recently shown that for nuclei near the N 126 and Z 82 shell closures, anisotropic a emission in favored decays, i.e., in transitions which are (almost) unhindered compared to the ground-state-to-ground-state transitions in neighboring even-even nuclei, is not dominated by deformation but rather by nuclear structure effects [12]. One is thus lead to the conclusion that the assumed relation between nuclear deformation and the angular distribution of a particles is not evident. It may be noted here that only the higher order partial a waves with angular momentum L fi 0 determine the a anisotropy. The a decay of unoriented nuclei is isotropic in space and hence decay rate experiments are i...

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Section: Nucleusmentioning

confidence: 98%

Section: Nucleusmentioning

confidence: 99%

“…In Ref. [22] no prediction for 229 Pa was given. The reason for the difference between experiment and theory is not very clear.…”

Section: Nucleusmentioning

confidence: 99%