An ion cooler-buncher for high-sensitivity collinear laser spectroscopy at ISOLDE

Mané, E.; Billowes, J.; Blaum, Klaus; Campbell, P.; Cheal, B.; Delahaye, P.; Flanagan, K.T.; Forest, D. H.; Frånberg, H.; Geppert, Christopher; Giles, T.; Jokinen, A.; Kowalska, M.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Podadera, I.; Tungate, G.; Vingerhoets, Pieter; Yordanov, Deyan T.

doi:10.1140/epja/i2009-10828-0

Cited by 98 publications

(68 citation statements)

References 13 publications

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“…The Ga yield was selectively enhanced by a factor of 100 using the Resonant Ionization Laser-Ion Source [17], extracted and accelerated to 30 keV and mass selected. The ions were cooled and bunched by the newly-installed ISCOOL [4] and delivered to the collinear laser spectroscopy setup [18]. The ion beam was…”

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confidence: 99%

“…The sensitivity of the laser technique has been critically enhanced using bunched beams from a gas-filled linear rf quadrupole known as an ion beam cooler [3]. In this Letter we report the application of ISCOOL [4]-an ion beam cooler recently installed at ISOLDE-for collinear laser spectroscopy on Ga isotopes from stable to the magic N ¼ 50 shell gap, located 15 isotopes away from stability. For the first time g.s.…”

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Nuclear Spins and Moments of Ga Isotopes Reveal Sudden Structural Changes betweenN=40andN=50

et al. 2010

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Collinear laser spectroscopy was performed on Ga (Z ¼ 31) isotopes at ISOLDE, CERN. A gas-filled linear Paul trap (ISCOOL) was used to extend measurements towards very neutron-rich isotopes (N ¼ 36-50 Nuclear structure has for some time been described by the single-particle (SP) states of nucleons in the shell model. The evolution and reordering of these levels along isotopic chains is explored at radioactive ion beam facilities to provide information on the nature of the nucleonnucleon interaction. Key to these studies is the determination of the value of the nuclear spin of each state, which provides a means of level identification. Whereas the spin may sometimes be inferred from nuclear decay and -spectroscopy data, laser spectroscopy [1,2] permits a measurement of the nuclear spin, in addition to the state's magnetic dipole and electric quadrupole moments. The latter two observables are very sensitive to the wave function and thus to the SP shell evolution. The sensitivity of the laser technique has been critically enhanced using bunched beams from a gas-filled linear rf quadrupole known as an ion beam cooler [3]. In this Letter we report the application of ISCOOL [4]-an ion beam cooler recently installed at ISOLDE-for collinear laser spectroscopy on Ga isotopes from stable to the magic N ¼ 50 shell gap, located 15 isotopes away from stability. For the first time g.s. spins have been measured, revealing sudden changes not observed in earlier experiments.The Ga isotopes have three protons outside the Z ¼ 28 shell gap. In a normal shell-model ordering, the three protons would occupy the p 3=2 level, leading to a g.s. spin I ¼ 3=2 for all odd-A Ga isotopes. However, in the Cu isotones with two protons fewer, it has been demonstrated that the proton SP ordering changes when neutrons start occupying the g 9=2 orbital around N ¼ 40 [5][6][7][8][9][10][11][12][13][14][15]. An inversion of the p 3=2 and f 5=2 SP levels was established recently in 75 Cu at N ¼ 46 [11], where the 5=2 À g.s. is near degenerate with a 3=2 À and 1=2 À state [11]. In this Letter we establish the g.s. spins and structure of the odd-A Ga isotopes from N ¼ 36 up to the N ¼ 50 shell closure, and we investigate the systematics of the 1=2 À , 3=2 À and 5=2 À levels.Fission fragments were produced in a thick UC x target (45 g=cm 2 ) using 1.4 GeV protons at an average current of $2 A. A proton-neutron converter [16] was used to suppress the Rb production. The Ga yield was selectively enhanced by a factor of 100 using the Resonant Ionization Laser-Ion Source [17], extracted and accelerated to 30 keV and mass selected. The ions were cooled and bunched by the newly-installed ISCOOL [4] and delivered to the collinear laser spectroscopy setup [18]. The ion beam was

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Nuclear Spins and Moments of Ga Isotopes Reveal Sudden Structural Changes betweenN=40andN=50

et al. 2010

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“…The resonant ionization laser ion source (RILIS) was used to stepwise resonantly laser ionize the Cu atoms within the ionizer tube [25]. The ions produced were accelerated through 30 kV and mass separated by the high resolution separator (HRS) before they were injected into a radiofrequency quadrupolar (RFQ) linear gas-filled Paul trap (ISCOOL) [26], which was floated at about 100 V below the ion-source acceleration potential. The application of ion cooling and bunching in collinear laser spectroscopy has been demonstrated in Jyväskylä (Finland) [27].…”

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Experimental determination of anIπ=2−ground state inCu72

et al. 2010

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This article reports on the ground-state spin and moments measured in 72,74 Cu using collinear laser spectroscopy at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. From the measured hyperfine coefficients, the nuclear observables µ( 72 Cu) = −1.3472(10)µ N , µ( 74 Cu) = −1.068(3)µ N , Q( 72 Cu) = +8(2) efm 2 , Q( 74 Cu) = +26(3) efm 2 , I ( 72 Cu) = 2, and I ( 74 Cu) = 2 have been determined. Through a comparison of the measured magnetic moments with different models, the negative moment reveals a strong πf 5/2 ⊗ νg 9/2 component in the ground-state wave function. Consequently, a negative parity has been assigned to the ground states of 72,74 Cu. Large-scale shell-model calculations illustrate the strong sensitivity of the nuclear moments to configuration mixing and to the effective interaction employed. The neutron-rich nuclei surrounding the Z = 28 and N = 50 shell closures have received a great deal of experimental and theoretical attention in the last decade. This region presents a key proving ground for the latest shell-model interactions, since it offers an attractively simple structure of the excited states in terms of particle-particle or particle-hole couplings. A compelling question in this region is related to the rapid reduction in energy of the 5/2 − state as the νg 9/2 orbital is filled in the Cu isotopes [1,2]. Given that this state remains static at approximately 1 MeV as neutrons fill the fp shell, its abrupt change at N = 40 garnered a great deal of interest and motivated further experimental and theoretical attention [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. A major step in understanding the evolution of nuclear structure in this region was the suggestion to include the monopole term from the tensor force interaction [18,19]. This work predicted a reduction in energy of the 5/2 − state and an inversion with the 3/2 − state in the mid-shell region, which was recently confirmed to occur at N = 46 in the odd-Cu isotopes [20]. Effective shell-model interactions which include this effect have recently been developed in the fpg model space. Two of these interactions start from a 56 Ni core [21,22], while the most recent one also includes excitations of protons from the πf 7/2 orbit across Z = 28 [23]. The odd-odd Cu isotopes are an ideal testing ground for these models, as their properties are extremely sensitive to the proton-neutron interaction.Recent beta-decay studies of 72 Ni [8] have tentatively assigned a spin I = 2 to the ground state (gs) of 72 Cu. Shell-model calculations, based on effective and realistic interactions, could not reproduce such gs spin [8], but placed the 2 − and 2 + states around 400 keV. A gs spin I = 2 is particularly interesting since the spins of 71,73 Cu now have been measured as I = 3/2, and their magnetic moments are compatible with a leading πp 3/2 configuration [20]. However, a [πp 3/2 ⊗ νg 3 9/2 , σ = 1] cannot couple to spin 2, so this configuration cannot be the leading term in the gs wave function of 72 Cu. Alternatively it could be...

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“…The isotopes of interest were mass separated by the high resolution mass separator (HRS) [25]. Cooling and bunching of the ions was performed with the use of the ISCOOL radio-frequency gas-filled linear Paul trap [28,29]. The release time for these bunches was synchronized with the duty cycle of the laser system.…”

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Laser and decay spectroscopy of the short-lived isotope Fr214 in the vicinity of the N=126 shell closure

et al. 2016

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Combined decay and laser spectroscopy measurements of the isotope 214 Fr are reported, using the collinear resonance ionization spectroscopy (CRIS) technique at the ISOLDE facility at CERN. For the I π = (1 − ) spin assignment, the g-factor value of g( 214 Fr) = +0.241(16) corresponds to a relatively pure (π 1h 9/2 ⊗ ν2g 9/2 ) ground-state configuration. An alternative interpretation with g( 214 Fr) = +0.144(10), for a (2 − ) spin assignment suggests a greater contribution of configuration mixing with the ν1i 11/2 orbital. As the N = 126 shell closure is passed, a kink is observed at the δ r 2 213,214 value, which is analogous to the behavior observed in the neighboring isotopic chains.

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An ion cooler-buncher for high-sensitivity collinear laser spectroscopy at ISOLDE

Cited by 98 publications

References 13 publications

Nuclear Spins and Moments of Ga Isotopes Reveal Sudden Structural Changes betweenN=40andN=50

Nuclear Spins and Moments of Ga Isotopes Reveal Sudden Structural Changes betweenN=40andN=50

Experimental determination of anIπ=2−ground state inCu72

Laser and decay spectroscopy of the short-lived isotope Fr214 in the vicinity of the N=126 shell closure

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