E. Arnold

Nuclear spin and magnetic moment of 11Li

Abstract Nuclear spin and magnetic moment of 11Li have been measured by optical pumping of a fast atomic beam. The angular asymmetry of the β-radiation from the polarized nuclei was used to detect the hfs of the 2s 2 S 1 2 −2 p 2 P 1 2 resonance line and the NMR signal cubic LiF crystal lattice. The results I= 3 2 and μI=3.6673(25) n.m. indicate a pure 1p 3 2 state of the valence proton.

Quadrupole moment of 11Li

Abstract The quadrupole coupling constants of 11Li and 9Li in LiNBO3 have been measured by β-NMR spectroscopy on implanted lithium nuclei. These were polarized by optical pumping on a fast beam of neutral atoms. The deduced ratio of quadrupole moments, |Q( 11 Li)/Q( 9 Li)|=1.14(16) , is in accordance with the current models describing the 11Li nucleus as being clustered into a 9Li core and halo of two loosely bound neutrons.

Laser-spectroscopy measurements of 72–96Kr spins, moments and charge radii

Abstract The spins, moments and radii of krypton isotopes have been investigated by collinear fast-beam laser spectroscopy in combination with ultra-sensitive collisional ionization detection. The sequence of isotopes under study ranges from the neutron-deficient N = Z = 36 isotope 72 Kr to the neutron-rich 96 Kr ( N = 60). The mean-square charge radii in the neighbourhood of the N = 50 neutron-shell closure exhibit a pronounced shell effect which has recently been explained in the framework of relativistic mean-field theory. The results for the neutron-deficient nuclei are related to the shape coexistence of strongly prolate and near-spherical states which is known from nuclear spectroscopy. Here, an inversion of the odd-even staggering is observed below the neutron number N = 45. The neutron-rich transitional nuclei are influenced by the N = 56 subshell closure. In contrast to the N = 60 isotones 97 Rb, 98 Sr and 100 Zr, the new isotope 96 Kr is not strongly deformed.

Xenon isotopes far from stability studied by collisional ionization laser spectroscopy

Abstract The new collisional ionization scheme in collinear laser spectroscopy has enabled the study of hyperfine structures and isotope shifts of xenon isotopes over the large mass range A = 116−146. The sensitivity of this method is demonstrated by the discovery of 146 Xe. Mean square charge radii, and spins and moments of the neutron-rich isotopes 137,139,141,143 Xe are deduced and discussed in comparison with earlier results on barium.

Quadrupole moments and nuclear shapes of neutron-deficient gold isotopes

Abstract The hyperfine structure splitting and the isotope shift of the neutron-deficient gold isotopes 194−191Au in the optical transition 5 d 9 6 s 2 2 D 3 2 → 5 d 10 6 p 2 P 1 2 (627.8 nm) have been determined by collinear laser spectroscopy at the on-line isotope separator ISOLDE. The nuclear magnetic moments, spectroscopic quadrupole moments and changes in the mean square charge radii are deduced. Experimental electromagnetic moments and deformation parameters are compared with results of a particle-triaxial-rotor model calculation for both odd-A and odd-odd gold nuclei. Very good overall agreement between calculation and experimental data has been achieved. We find, for the first time, consistent evidence for a relatively large contribution from hexadecapole deformation (ϵ4 = 0.06, β4 = −0.05) to odd-A gold isotopes ground states in the region of 183 ≤A ≤ 197. Calculated values of quadrupole deformation are consistent with the prolate-to-oblate shape change between ground states of 186Au and 187Au. In addition, our results suggest another shape change between 190Au (oblate) and 191Au (triaxial). The former change is accompanied by a considerable change in quadrupole deformation, the latter occurs at almost constant deformation.

Nuclear moments of strongly deformed strontium isotopes

Nuclear spins, moments and mean square charge radii of78–100Sr have been obtained by fast ion-beam collinear laserspectroscopy. The experiments performed at ISOLDE have been extended to include99Sr, measured by a non-optical detection scheme with a two-step optical pumping sequence. The results for the strongly deformed isotopes are discussed in the frame of the particle-plus-deformed core model.

TOTAL CROSS-SECTIONS OF REACTIONS INDUCED BY NEUTRON RICH LIGHT NUCLEI

Total nuclear reaction cross-sections are determined by means of a 4π-γ method. The results cover a wide span of targets for various stable beams. The validity of the method is shown in a combined systematics including also the results of transmission-type experiments. The data are very well described by the formula developed by Kox et al. The same method is applied to secondary fragment beams produced from a 44 MeV/u22Ne beam on a 332mg/cm2181Ta target. Using the LISE spectrometer the fragments4, 6He,6–9, 11Li,7, 9–12, 14Be,10–15, 17B11–19C,13–19N,15–21O,18– 21F and20,21 Ne are analyzed and transported to interact with a 199.4 mg/cm2 Cu target surrounded by a 4π-γ counter. The measured total reaction cross-sectionsσR are discussed in terms of the reduced strong absorption radiusr0 and compared with other experimental results.

Very high sensitivity in collinear laser spectroscopy: resonance detection by particle counting techniques

Abstract Fast-beam collinear laser spectroscopy with resonance detection by counting of fluorescence photons provides a versatile tool for precise determinations of nuclear ground-state properties. The intrinsic high sensitivity of this method can be further increased by almost three orders of magnitude if measuring schemes based on ion or atom counting are introduced. The optical pumping from one atomic state to another at an appreciably different excitation energy is detected via state-selective collisional charge exchange processes and charge-state separated atom or ion counting. Applications of these techniques on alkaline earth, noble gas, mercury and thallium beams is examined.

Nuclear ground-state spins of short-lived strontium isotopes

Nuclear ground state spins of the odd-mass strontium isotopes between A=79 and 97 were determined by measurements of the hyperfine structure in the ionic transition 5s2S1/2−5p2P3/2. The spins of93Sr and97Sr are revised to I=5/2 and I=1/2, respectively, while assignments for the remaining isotopes are confirmed.

The quadrupole moment of the neutron-halo nucleus11Li

The quadrupole moment ratio of 9Li and 11Li was measured by a combination of in-beam laser induced nuclear polarization and β-NMR in LiNbO3. The result |Q(11Li)/Q(9Li)| = 1.14(16) is consistent with cluster models describing 11Li as composed of a 9Li core and a far extended halo of two loosely bound neutrons.