Collinear laser spectroscopy was performed on the nuclear ground states of the neutron-deficient isotopes (206,205,204)Fr. A new technique was developed to suppress hyperfine pumping in collinear laser spectroscopy of atoms. This involved high-frequency intensity modulation of narrow-linewidth laser light using fast-switching electro-optical modulators. The nuclear ground-state spins of (206,205,204)Fr were determined to be 3, 9/2, and 3, respectively. Both the changes in mean-squared charge radii and nuclear magnetic dipole moments indicate a departure from single-particle estimates.
Collinear-laser spectroscopy with bunched-beams technique was used for the study of neutron deficient Rb isotopes, out to 74 Rb (N = Z = 37) at TRIUMF. The measured hyperfine coupling constants of 76,78m Rb were in agreement with literature values. The nuclear spin of 75 Rb was confirmed to be I = 3/2, and its hyperfine coupling constants were measured for the first time. The mean-square charge radius of 74 Rb was determined for the first time. This result has improved the isospin symmetry breaking correction term used to calculate the Ft value, with implications for tests of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.The unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is one of the cornerstones of the Standard Model of particles and fields. Therefore, the value of all its matrix elements should be measured as accurately and as precisely as possible for the search of new physics phenomena, such as the existence of right-handed currents, extra Z bosons or another quark generation [1]. Indeed, over the years, the value of these matrix elements have been independently determined from different experiments. Superallowed Fermi transitions of nuclear beta decays (0 + → 0 + ) provide the most competitive method to determine the up-down quark matrix element V ud [2]. Assuming the Conserved Vector Current (CVC) hypothesis, which states that the vector coupling constant of semileptonic weak interactions G V remains unchanged in all superallowed beta transitions, this matrix element can be obtained from V ud = G V /G F , where G F is the weak interaction constant for leptonic muon decay, and G V is defined in terms of the corrected F t value of the beta decay [3],.The f t value is related to the measured half-lives, branching ratios and the Q value of the beta decay. The terms δ ′ R and δ N S are transition-dependent theoretical corrections, and δ C is the isospin symmetry breaking term [4]. The latter is purely nuclear structure dependent, the error of which normally dominates the uncertainty on the F t value. The term ∆ V R is transition-independent and K is a constant. Evaluations of the isospin symmetry breaking correction involve the 13 most precisely measured superallowed beta emitters which span a wide Z range (6 ≤ Z ≤ 37) [4]. Within the existing theoretical approaches used to determine δ C [5] the leading source of uncertainty stems from the incomplete knowledge of the radial extension of the charge distribution of the parent and daughter isotopes. Where experimental data are unavailable, the nuclear structure input is based on extrapolations of the existing models. For the lighter elements, shell model calculations with a Saxon-Woods potential provide a more consistent framework from which this information can be reliably extracted. However, with higher Z, the orbitals of the f p shell are filled and shell model calculations become computationally difficult, due to the larger model space required. In addition, effective interactions become less reliable [6]. There have been many theoretical ef...
The ratio of electric quadrupole moments of 11Li and 9Li was measured using the zero-field β-detected nuclear quadrupole resonance technique at Triumf-Isac. The precision on the ratio Q11/Q9 = 1.0775(12) was improved by more than one order of magnitude and an absolute value for the quadrupole moment of 11Li was inferred. Systematic effects, as argued here, are not expected to contribute to the ratio on this scale. The zero-field spin-lattice relaxation time for 8Li implanted within SrTiO3 at 295 K in zero-field was found to be T1 = 1.73(2) s. A comparison of the quadrupole moments of 9, 11Li and their ratio is made with the latest models, however, no conclusion may yet be drawn owing to the size of the theoretical uncertainties.
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