The sign of the multiple Coulomb excitation interference term and the static quadrupole moment of the first 2+ state of 114Cd

doi:10.1016/0375-9474(72)90725-7

Nuclear Physics A

Volume 195, Issue 1, 6 November 1972, Pages 119-128

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Abstract

A Coulomb excitation experiment has been performed on the first 2⁺ state of ¹¹⁴Cd. Thin foils of enriched ¹¹⁴CdO were bombarded by 50 MeV ³²S ions. The relative excitation probabilities of the first 2⁺ state were measured at backward and forward projectile scattering angles. Particle-γ coincidences were used to identify the inelastic events. The data were analyzed with the aid of the Winther-De Boer multiple Coulomb excitation program. The projectile and its bombarding energy were chosen to minimize the effect on the experiment of Coulomb excitation of the first 2⁺ state via the second 2⁺ state. By comparing the results of this work with the results of the high excitation probability experiment of Berant et al., it was possible to deduce that the sign of the interference term due to Coulomb excitation of the first 2⁺ state via the second 2⁺ state is positive. The static quadrupole moment of the first 2⁺ state was determined to be Q_2⁺ = −0.35±0.07 b.

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The static electric quadrupole moments Q(2₁⁺) of the first excited states of ^138,134,130Ba and the reduced transition probabilities B(E2;O₁⁺→ 2₁⁺) have been measured using the reorientation effect in Coulomb excitation. It is found for ¹³⁸Ba that Q(2₁⁺) = −0.14 (7) [0.08 (7)] e · b, where in this and the following cases the unbracketed value corresponds to constructive interference from the 2₂⁺ state and the bracketed value corresponds to destructive interference; for $^{134} Ba Q(2_{1}^{+}) = −0.32 (6) [0.09 (6)] e · b$ for P₃(4₁⁺) < 0 or Q(2₁⁺) = −0.20 (6) [0.21 (6)] e · b for P₃(4₁⁺) > 0; for ¹³⁰Ba if it is assumed that the mixing ratio δ(E2/M1; 2₂⁺→2₁⁺) > 1 then Q(2₁⁺) = -1.02 (15) [−0.09 (15) ] e · b. Results obtained for B(E2; O₁⁺→ 2₁⁺) are 0.241 (6) e² · b², 0.655 (6) e² · b² and 1.167(11)[1.159 (12)] e² · b² for $^{138},134,130 Ba$ respectively. The results are compared with previous measurements and with the predictions of various nuclear models.
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A formulation of the boson expansion technique given in our previous publication has been developed further by adding the contributions of the quadrupole-pairing interaction and the coupling between the collective and noncollective modes of excitations. Based on this formalism numerical calculations were carried out to describe the properties of a number of collective nuclei found in various regions of the periodic table. In general, very good agreement with experiment was obtained both for vibrational and rotational nuclei. Comparison with earlier theoretical work is also made.

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^††: Work supported by the National Science Foundation.

^†: Present address: University of Wisconsin, Madison, Wisconsin, USA.

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Nuclear Physics A

Abstract

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Electric quadrupole moments of the first excited states of <sup>130,134,138</sup>Ba

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Measurement of the static quadrupole moments of the first 2<sup>+</sup> states in <sup>76</sup>Se, <sup>78</sup>Se, <sup>80</sup>Se and <sup>82</sup>Se

Description of nuclear collective motions in terms of the boson expansion technique. (II). Additional formulation and numerical calculations