Search

Background: The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible.Purpose: Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in $^{106}\mathrm{Cd}$.Methods: In an inverse kinematics reaction, a $^{106}\mathrm{Cd}$ beam impinging on a $^{12}\mathrm{C}$ target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure $g$ factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for $^{106}\mathrm{Cd}$.Results: The $g$ factors of the ${2}_{1}^{+}$ and ${4}_{1}^{+}$ states in $^{106}\mathrm{Cd}$ were measured to be $g({2}_{1}^{+})=+0.398(22)$ and $g({4}_{1}^{+})=+0.23(5)$. A lineshape analysis yielded lifetimes in disagreement with published values. The new results are $\ensuremath{\tau}(^{106}\mathrm{Cd};{2}_{1}^{+})=7.0(3)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ and $\ensuremath{\tau}(^{106}\mathrm{Cd};{4}_{1}^{+})=2.5(2)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$. The mean life $\ensuremath{\tau}(^{106}\mathrm{Cd};{2}_{2}^{+})=0.28(2)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ was determined from the fully-Doppler-shifted $\ensuremath{\gamma}$ line. Mean lives of $\ensuremath{\tau}(^{106}\mathrm{Cd};{4}_{3}^{+})=1.1(1)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ and $\ensuremath{\tau}(^{106}\mathrm{Cd};{3}_{1}^{\ensuremath{-}})=0.16(1)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ were determined for the first time.Conclusions: The newly measured $g({4}_{1}^{+})$ of $^{106}\mathrm{Cd}$ is found to be only 59% of the $g({2}_{1}^{+})$. This difference cannot be explained by either shell-model or collective-model calculations.

In this study, the structure of the semimagic Sn50 isotopes were previously studied via measurements of B(E2;21+ → 01+) and g factors of 21+ states. The values of the B(E2;21+) in the isotopes below midshell at N = 66 show an enhancement in collectivity, contrary to predictions from shell-model calculations. This work presents the first measurement of the 21+ and 41+ states' magnetic moments in the unstable neutron-deficient 110Sn. The g factors provide complementary structure information to the interpretation of the observed B(E2) values.

The g factors of the 2 1 + and 4 1 + states in radioactive 52 Ti ( T 1 / 2 = 1.7 m ) have been measured for the first time using the technique of α transfer to 48 Ca beams in inverse kinematics, in combination with transient magnetic fields. In addition, employing the Doppler-shift-attenuation method, the lifetime of the 2 1 + state has been re-determined with much higher precision while the lifetime values of the 4 1 + and the 2 3 + states were obtained for the first time. The B ( E 2 ) and g factor results were compared with the results obtained within the framework of full fp spherical shell model calculations using several recent effective interactions commonly utilized in this mass region. The two measured g factors were accounted for by none of the calculations except for the FPD6 calculation with modified input single-particle energies. The new data were also discussed in relation to the neighbouring isotopes, 48,50 Ti, isotones, 50,52,54 Cr, and the magic N = 28 shell closure. Our calculations generally reproduce well the trends of the data in terms of their dependence on neutron number.

Measurements of g factors and lifetimes of the 2 1 + states in 36,38Ar have been performed via α-transfer reactions using 32S and 34S ions in inverse kinematics combined with the techniques of transient magnetic fields and Doppler-shift-attenuation. The variations, with the neutron number, of the measured g factors and B ( E 2 ) values of 36,38,40Ar have been explained by large-scale shell model calculations. The good agreement achieved between experiment and theory demonstrates the impact of the effective nucleon–nucleon interactions and the magic N = 20 shell closure. The present new results are a very good show-case for the universal difference in sensitivity of excitation energies, magnetic moments and electromagnetic transition probabilities to nuclear wave functions behaviour as closed shells are approached, crossed, and left behind. Aspects of the collectivity of these nuclei are also discussed from the perspective of a simple vibrational model.

The Rare ISotopes INvestigation at GSI project combines the former EUROBALL Ge-Cluster detectors, the MINIBALL Ge detectors, BaF2--HECTOR detectors, and the fragment separator at GSI for high-resolution in-beam gamma-ray spectroscopy measurements with radioactive beams. These secondary beams produced at relativistic energies are used for Coulomb excitation or secondary fragmentation experiments in order to explore the nuclear structure of the projectiles or projectile like nuclei by measuring de-excitation photons. The newly designed detector array is described and the performance characteristics are given. Moreover, particularities of the experimental technique are discussed.

The g factor of the first excited 2 + state in 46 Ca has been remeasured with better accuracy than previously obtained, g(2 + , 46 Ca) =− 0.26(6). The experiment utilized the transient field technique combined with Coulomb excitation in inverse kinematics. This result was analyzed in terms of shell model plus deformed core calculations. The positive g factors of the 2 + states in 42 Ca and 44 Ca suggest that the 2 + state wave functions require significant particle–hole excitations of the Z = 20, N = 20 core. The new data for 46 Ca show that (fp) 6 configurations dominate near the shell closure at 48 Ca and indicate that core excitation plays a lesser role than was hitherto believed.

Measurements of nuclear spin precessions in the transient field (TF) of ferromagnetic gadolinium have provided for the first time evidence for demagnetization effects induced by the energy loss of traversing Mg ions. The primary electronic spike associated with the host electrons is probed in space and time on a nanometer and femtosecond scale by Coulomb-excited 76,80Se ions recoiling in and near the tracks of preceding 26Mg ions. The demagnetization that reduces the TF strength is observed via the spin precession of the Se probe ions. The present measurements are sensitive solely to the electronic spike and not to a succeeding lattice spike, as the lattice temperature is substantially lower than the Curie temperature and its build-up occurs significantly later in time than the interaction of the probe ions in the ferromagnet.

The g factor of the first 2+ state of radioactive 76Kr (T1/2=14.8 h) has been measured, extending the systematics of the previously measured stable 78, 80, 82, 84, 86Kr isotopes. The measurement was performed with a radioactive 76Kr ion beam applying projectile Coulomb excitation in inverse kinematics combined with the transient magnetic field technique. The 76Kr beam was produced and accelerated in batch mode (re-cyclotron method) at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. A total of three production and acceleration cycles yielded six hours of beam on target with peak rates of 108 particles/s. About 5.6×104 particle-γ coincidence events were recorded. The g factor g( 76 Kr ;2 + 1 )=+0.37(11) was obtained by direct comparison to the known g( 78 Kr ;2 + 1 ) value re-measured immediately after the 76Kr runs with the same setup and under almost identical kinematic conditions.

The g factors of the 21+ states in 42,44 Ca have been measured employing Coulomb excitation of isotopically pure calcium beams in inverse kinematics combined with the transient field technique. In addition, the lifetimes were redetermined using the Doppler-shift-attenuation method. While the g factor of 44 Ca (2 1 + ) has definitely a positive value, g=+0.17(3), for 42 Ca a vanishingly small g factor, g(21+)=+0.04(6), was observed in a very first measurement. These are striking results since one expects for an assumed inert 40 Ca core with two or four valence neutrons in the fp shell a negative g factor, g≃−0.4, in accordance with experimental data for the 7/2− ground states of the odd neighbouring isotopes. Therefore, the new experimental findings clearly require substantial admixtures of configurations from sd shell core excitations in the wave functions of the nuclear states. A “co-existence” picture, along the lines of Gerace and Green, suggests core-deformed components in the 2+1 state of 55(6)% and 66(4)% in 42 Ca and 44 Ca , respectively. A separate large scale shell model calculation in the (sd−fp) shell space results in good overall agreement with the experimental data.

The g factor of the 2 1 + state in radioactive 44 Ti has been measured for the first time with the technique of α transfer to 40 Ca beams in inverse kinematics in combination with transient magnetic fields, yielding the value, g (2 1 + )=+0.52(15). In addition, the lifetimes of the 2 1 + , τ =3.97(28) ps, and the 4 1 + states, τ =0.65(6) ps, were redetermined with higher precision using the Doppler shift attenuation method. The deduced B (E2)'s and the g factor were well explained by a full fp shell model calculation using the FPD6 effective NN interaction. The g factor can also be accounted for by a simple rotational model ( g = Z / A ). However, if one also considers the B (E2)'s and the E (4 1 + )/ E (2 1 + ) ratios, then an imperfect vibrator picture gives better agreement with the data.

The g factors of the 2 + 1 and 3 − 1 states in 96 Zr have been measured for the first time by Coulomb excitation of 96 Zr beams in inverse kinematics using transient magnetic fields. The resulting g factors are g (2 + 1 )=+0.03(7) and g (3 − 1 )=+0.98(15). The lifetime of the 2 + 1 state, τ =0.82(10) ps, was redetermined via the Doppler Shift Attenuation Method. The 2 + 1 →0 + 1 transition rate and the g -factor data are in fair agreement with shell-model calculations involving both proton and neutron excitations. The pronounced octupole strength of the 3 − 1 →0 + 1 transition is not seen in the g factor which exceeds significantly an expected Z / A value.

In view of the puzzlingly small g factor, obtained for the 20 Ne(4 1 + ) state in previous measurements, in contradiction to all existing theoretical calculations, we have performed a new set of experiments that rigorously test the former results. Besides employing the same nuclear reaction for populating the nuclear states, new experimental features were introduced to exert strict control on the relevant parameters of the transient magnetic hyperfine field technique. The new result, g (4 1 + )=+0.38(8), is close to theoretical predictions.

Following the successful identification of mixed-symmetric one- and two-phonon states in the N=52 nuclei 94Mo and 96Ru, we have performed a photon scattering experiment on the N=52 isotone 92Zr. Experimental data and shell model calculations show that both, single particle and collective degrees of freedom are present in the low-lying levels of 92Zr. The second excited quadrupole state shows the signatures of the one-phonon mixed-symmetric 2+ state, while calculations and data indicate an almost pure neutron configuration for the 2+1 state, in contradiction with the F-spin symmetric limit. Furthermore, two strong dipole excitations, which are candidates for the two-phonon quadrupole–octupole coupled E1 excitation and for the mixed-symmetric 1+ two-phonon state, were observed.

For high precision measurements of magnetic moments and reduced transition probabilities by the combined technique of projectile Coulomb excitation in inverse kinematics and transient magnetic fields sandwich targets of carbon and gadolinium had to be developed. A Gd layer of 4 mg/cm 2 was evaporated onto 1–3 mg/cm 2 Ta backings heated to 800 K for optimum ferromagnetic properties of the Gd. A Cu film of 3.5 mg/cm 2 was then deposited on the reverse side of the Ta backing. The Cu was required for stopping the Coulomb excited beam ions in a hyperfine interaction-free medium and for cooling the Gd film below its Curie temperature. The sandwich was then completed with 0.5 mg/cm 2 nat C deposited onto the Gd. The adherence of evaporated carbon on the ferromagnetic gadolinium was found to be poor, and good results were not easily reproduced. Therefore, deposition of carbon by laser plasma ablation was also investigated.

The evolution of shell structure and the fragility of the benchmark magic numbers is a topic of major interest in nuclear-structure physics. The authors measured the structure-sensitive $g$ factors of states in unstable even-even strontium isotopes, following $\ensuremath{\alpha}$-pickup reactions by krypton beams from a carbon target. The results help elucidate how protons and neutrons contribute to the evolution of nuclear structure in this important mass region where rapid structural changes occur.

Recent experiments have shown that the technique of Coulomb excitation of beam ions in inverse kinematics, where the target nuclei are lighter than the beam, combined with transient magnetic fields, provides a powerful method to measure magnetic moments of short-lived nuclear states with high precision and efficiency. The method is directly applicable to measurements on radioactive beams. In the conventional experiments, the beam and the Coulomb excited projectiles are stopped in a multi-layered target, while the lighter target nuclei traverse the whole target and are detected around 0∘ in coincidence with projectile γ-rays. But even for low intensity radioactive beams, this technique would lead to an excessive accumulation of activity in the target. A method is presented here, in which the beam passes through the target and a hole in the particle detector and is stopped in a downstream beam dump shielded from the detectors. A test was carried out on the g factor of the 2+1 state of 50 Ti .

The g factors of the 4 + 1 and 6 + 1 states in 144,148 Nd, the 4 + 1 state in 146 Nd and the 4 + 1 , 6 + 1 , 8 + 1 and 10 + 1 states in 150 Nd have been measured for the first time by projectile Coulomb excitation combined with the transient field technique. The g factors of the 2 + 1 states in 144,146,148,150 Nd have been remeasured with very high precision. A pronounced transition in the structure of these isotopes occurs as neutrons are removed from the rotational 150 Nd and shell closure at N =82 is approached. The g factors unambiguously reflect the increasing strength of the (2 f 7/2 ) ν n configuration.

The g factors of the 2 + 1 and 3 − 1 states in semi-magic 90 Zr have been measured for the first time with the technique of Coulomb excitation of 90 Zr beams in inverse kinematics in combination with transient magnetic fields. The resulting g factors, g (2 + 1 )=+1.25(21) and g (3 − 1 )=+0.986(56), are both consistent with a dominant g 9/2 proton configuration and a closed N =50 neutron shell. The lifetime of the 2 + 1 state was measured by the Doppler shift attenuation method, τ =0.126(3) ps.

Measurements of magnetic moments and lifetimes of ${2}_{1}^{+}$ and ${4}_{1}^{+}$ states of ${}^{46,48}\mathrm{Ti}$ and ${}^{50,52}\mathrm{Cr}$ were performed with high accuracy via projectile Coulomb excitation and the technique of transient magnetic fields. The high quality of the data allows for the first time to establish stringent constraints on large scale shell model calculations. Whereas the global behavior of the data is well explained by full $\mathrm{fp}$ shell model calculations, distinct deviations in the $g$ factors and $B(E2)$ values of ${}^{46,48}\mathrm{Ti}$ from theoretical predictions can be attributed to excitations of the ${}^{40}\mathrm{Ca}$ core. This suggestion is supported by recent Monte Carlo calculations which provide evidence that ${}^{48}\mathrm{Ca}$ is a better inert core.

g factors of the 2 + 1 and 4 + 1 states in 92,94 Zr have been measured via Coulomb excitation of isotopically pure 92,94 Zr beams in inverse kinematics in combination with the transient field technique. The high precision results, g ( 92 Zr; 2 + 1 ) = −0.180(10) and g ( 94 Zr; 2 + 1 ) = −0.329(15) as well as the new data on the 4 + 1 state, g ( 92 Zr; 4 + 1 ) = −0.50(11), provide, for the first time, clear evidence of the dominant role of d 5/2 neutrons in the wave functions of these nuclei just above the N =50 shell closure. Moreover, the data imply increased purity of the d 5/2 neutron component in the wave function with increasing spin.

We report on "safe" Coulomb excitation of neutron-rich (138,140,142) Xe nuclei. The radioactive nuclei have been produced by ISOLDE at CERN and post-accelerated by the REX-ISOLDE facility. The gamma-rays emitted by the decay of excited states have been detected by the MINIBALL array. Recent results are presented.

Measurements of transient magnetic fields (TF) were performed for the first time in the amorphous compounds of Fe80B20 and Fe85B15 for 24Mg(2+), 28Si(2+), 48Ti(2+) and 56Fe(2+) probe ions employing light and heavy ion beams. The motivation for these experiments was to investigate whether ion beam induced attenuations of TF are substantially weaker in these materials than in crystalline Fe. This expectation was indeed satisfied. The attenuations observed were found to be smaller at least by a factor of 2.

Measurements of transient (TF) and static (SF) magnetic hyperfine fields at 56 Fe(2 + ) ions, implanted in Fe host after Coulomb excitation using 16 O- and 56 Fe-beams, exhibit attenuations of the SF strength which is shown for the first time to be primarily due to the effect of the ion beam and only secondarily to that of the recoil ion. The beam induced attenuation is of the same nature and magnitude as for TF, which has been determined in former measurements. It must therefore arise from the depolarization of the Fe 3d electrons resulting from the ion stopping. The effect of the recoil implanted ion may be attributed to a thermal spike which seems to be more efficient for heavier probe ions.

Measurements of transient magnetic fields (TF) were performed on swift heavy ions of56Fe and80Se, with Coulomb excitation of their first 2+ state as probe, traversing thin Fe layers with segmented and unsegmented structures. The 50 µm×50 µm squares of the segments were accomplished applying the techniques of photolithography and ion etching. The magnitude of the TF deduced clearly shows that by segmentation of the targets the ion beam induced attentuations can be eliminated. This finding has direct applications tog-factor measurements.

Heavy ion beams induce by their stopping power severe demagnetizations of ferromagnetic materials of dynamic nature. This perturbation of ferromagnetism causes substantial attenuations of transient magnetic fields on traversing probe ions. A striking stopping power dependence has been found when the probe ions are in the H-like charge state. Due to the uncorrelated behaviour of beam ions and probe ions , moving on different trajectories through the ferromagnetic sample, the demagnetization, initially located at the ionization track of the beam ion, must propagate to the region of the probe ion. The determination of the range of demagnetization from its origin was the subject of the present measurements.

Background: The $g$ factors and lifetimes of the 2${}_{1}^{+}$ states in the stable, proton-rich Sn isotopes have been measured, but there is scant information on neutron-rich Sn isotopes.Purpose: Measurement of the $g$ factor and the lifetime of the 2${}_{1}^{+}$ state at 1.141 MeV in neutron-rich ${}^{126}$Sn (${T}_{1/2}=2.3\ifmmode\times\else\texttimes\fi{}{10}^{5}y$).Method: Coulomb excitation in inverse kinematics together with the transient field and the Doppler shift attenuation techniques were applied to a radioactive beam of ${}^{126}$Sn at the Holifield Radioactive Ion Beam Facility.Results: $g({2}_{1}^{+})=\ensuremath{-}0.25(21)$ and $\ensuremath{\tau}({2}_{1}^{+})=1.5(2)$ ps were obtained.Conclusions: The data are compared to large-scale shell-model and quasiparticle random-phase calculations. Neutrons in the ${h}_{11/2}$ and ${d}_{3/2}$ orbitals play an important role in the structure of the 2${}_{1}^{+}$ state of ${}^{126}$Sn. Challenges, limitations, and implications for such experiments at future rare isotope beam facilities are discussed.

Background: The evolution of and interplay between single-particle and collective excitations in the 40 $\ensuremath{\leqslant}N\ensuremath{\leqslant}$ 50 range for ${}_{38}$Sr and ${}_{40}$Zr isotopes have been studied.Purpose: Measurement of the $g$ factor of the 2${}_{1}^{+}$ and 4${}_{1}^{+}$ states in radioactive ${}^{88}$Zr while simultaneously remeasuring the $g({2}_{1}^{+})$ factors in the Sr isotopes and extention of the measurements to higher energy states in the Sr isotopes. Lifetimes of states in these nuclei are determined.Methods: The transient field technique in inverse kinematics and line-shape analysis using the Doppler-shift attenuation method are applied. The ${}^{88}$Zr nuclei were produced by the transfer of an $\ensuremath{\alpha}$ particle from the ${}^{12}$C nuclei of the target to ${}^{84}$Sr nuclei in the beam. The excited states in the stable ${}^{84}$Sr isotopes were simultaneously populated via Coulomb excitation by ${}^{12}$C in the same target. Coulomb excitation measurements on ${}^{86,88}$Sr were carried out with the same apparatus.Results: The resulting $g$ factors and $B(E2)$ values of these nuclei reveal similarities between the two chains of Zr and Sr isotopes. Large-scale shell-model calculations were performed within the ${p}_{3/2},{f}_{5/2},{p}_{1/2},{g}_{9/2}$ orbital space for both protons and neutrons and yielded results in agreement with the experimental data.Conclusions: In this paper the magnetic moments and lifetimes of several low-lying states in ${}^{88}$Zr and ${}^{84.86,88}$Sr have been measured and compared to large-scale shell-model calculations.

Background: The experimental study of $g(Ig2)$ factors of nuclear states can provide information about the evolution of collectivity in certain regions of the nuclear chart, and assist in obtaining a microscopic description of the nuclear wave functions. The measurements and explanations of $g(Ig2)$ factors are still a challenge for experiments and theory.Purpose: Measurement of the $g({2}_{1}^{+})$ and $g({4}_{1}^{+})$ factors, the latter for the first time, in the ${\phantom{\rule{0.16em}{0ex}}}_{44}^{96}$Ru nucleus. Comparison of the experimental results with calculations using the shell model and collective models.Methods: The experiments made use of the transient field technique, using a Coulomb-excitation reaction in inverse kinematics. Large scale shell model calculations were performed; comparisons with previous theoretical predictions, using the tidal-wave model and the hydrodynamical model, were carried out.Results: The values of $g({2}_{1}^{+})=+0.46(2)$ and $g({4}_{1}^{+})=+0.58(8)$ were experimentally obtained. While the $g({2}_{1}^{+})$ value agrees with the hydrodynamical model prediction of $g=Z/A=+0.46$, the $g({4}_{1}^{+})$ is in agreement with the shell model predictions. The trend of the experimental $g$ factors, as a function of nuclear spin, is not reproduced by the theoretical models discussed.Conclusions: Measurements of $g({2}_{1}^{+})$ and $g({4}_{1}^{+})$ in ${}^{96}$Ru were performed. Further theoretical efforts are necessary to explain the trend of the $g$ factors as a function of nuclear spin for the ${}^{96}$Ru nucleus. Future measurements of $g({4}_{1}^{+})$ should reduce the uncertainty of the result.

The g-factors of the 217, 523 and 761 keV levels in 79 Br have been measured using Coulomb excitation of 79 Br beams and transient field technique with Gd as ferromagnetic host. Lifetimes of several states have been determined using the Doppler-shift attenuation method. Mixing ratios of γ-transitions were deduced from measured angular correlations. The data are discussed in the framework of the weak particle-core coupling and the particle-axial-rotor coupling models.

Transient field (TF) precessions have been measured in Fe for high-velocity 28 Si ions following projectile Coulomb excitation of the first 2 + -state. In contrast to a recent measurement on 24 Mg ions which yielded at comparable velocity with the same geometry for the angular correlation an unexpected small TF, the present observations agree very well with the expectation of large TF: no diminution of the transferred polarization is found.

Ion-beam induced attenuations of transient magnetic fields have been further studied in measurements on high-velocity24Mg- and28Si-ions as well as low-velocity48Ti-ions using energetic beams of Ti- and Br-ions. Further evidence for the stopping power dependence of the attenuations is found; more data in the threshold region of Fe-host support earlier observations. In Gd-host the attenuations are again weaker pronounced than in Fe in accordance with previous data.

A precision plunger set-up was used to determine in time-differential measurements of hyperfine interactions the degree of polarization of 1s- and 2s-electrons in H- and Li-like oxygen ions on their emergence from magnetized Ni- and Gd-layers into vacuum. In addition a time-integral measurement with Fe-layers served to obtain the polarization of 2s-electrons only. For all three ferromagnetic materials the degree of polarization of 2s-electrons is found to be twice as large as for 1s-electrons. The data are discussed in the context of transient magnetic fields and their underlying polarization mechanism.

The g factors of the first excited 2(+) states in the Sn-112,Sn-114,Sn-116,Sn-122,Sn-124 isotopes have been measured with high accuracy using the transient field technique in combination with Coulomb excitation in inverse kinematics. The experimental results are discussed in a qualitative way on the basis of empirical single-particle g factors of the relevant proton and neutron orbitals and are compared to a number of different theoretical calculations. The results are found to be best described by shell-model calculations in an extended configuration space. Clear evidence for the contribution of neutron pair excitations from the 1d(3/2) to the 0h(11/2) orbital to the wave function of the 2(1)(+) state in Sn-122,Sn-124 has been obtained.

Precise measurements of the lifetimes of the first excited 2+ states in the stable even-A Sn isotopes 112-124Sn have been performed using the Doppler shift attenuation technique. For the isotopes 112Sn, 114Sn and 116Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously reported values and indicate a shallow minimum at N=66. The observed deviation from a maximum at mid-shell is attributed to the obstructive effect of the s1/2 neutron orbital in generating collectivity when near the Fermi level. © 2010 Elsevier B.V., Financial support from the Spanish Ministerio de Ciencia e Innovaci on under contracts FPA2007-66069, FPA2009-13377-C02-01 and FPA2009-13377-C02-02, the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042) and the Australian Re- search Council Discovery Scheme, grant no. DP0773273

Precise measurements of lifetimes in the picosecond range of excited states in the stable even-A Sn isotopes 112;114;116;122 Sn have been performed using the Doppler shift attenuation technique. For the rst excited 2 + states in 112 Sn, 114 Sn and 116 Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously adopted values. They indicate a shallow minimum at N = 66 in contrast to the maximum at mid-shell predicted by modern shell model calculations., Financial support from the Spanish Ministerio de Ciencia e Innovaci on under contracts FPA2007-66069 and FPA2009-13377-C02-02, and the Australian Research Council Discovery Scheme, grant no. DP0773273.

With the knowng-factor of the Coulomb excited first 2+-state in32S the transient magnetic field was determined for sulphur ions traversing Gd at a mean velocity of 16ν0 (ν0=c/137). The degree of polarization deduced for the dominating H-like ions, ¯p1s=0.10(3), agrees very well with that obtained at lower velocities. In addition, an upper limit of a transient electric field gradient was deduced from the particle-γ-angular correlation which is expected on theoretical grounds.

New data for electron polarization were obtained in transient field (TF) measurements for H-like ions at high velocities. Spin-exchange scattering calculations with the polarized electrons in bound states of the ferromagnetic host atoms are successful for explaining experimental data. The deteriorating effect of ion-beam-induced perturbations on the TF strength in ferromagnetic materials has been studied systematically. Concepts for its control or elimination are introduced and discussed.

The g -factors of the first 2 + states in 134, 136 Xe have been measured relative to the known value of 132 Xe(2 + 1 ) employing the transient-field technique with Fe as ferromagnetic host. Coulomb excitation with sulphur beams was applied to isotopically pure Xe targets. The lifetime of the 136 Xe(2 + 1 ) state has been redetermined using the Doppler-shift attenuation method. The value obtained tends to be shorter than the only published data.

Employing the time-differential perturbed γ-angular correlation technique it is shown that 1s- and2s-electrons of highly stripped16O(3−)-ions have their spin polarized on emergence from magnetized thin Ni- andGd-layers into vacuum. The mean degree of polarization of 2s-electrons is found to be twice as large as for 1s-electrons.

We have remeasured and have redetermined the $g$ factor for the ${4}_{1}^{+}$ state in $^{68}\mathrm{Zn}$ following inconsistencies between earlier measurements and a recent result. We have reanalyzed several former measurements by applying an alternative analysis procedure, which allows for determining the precession effect separately for each gamma detector implying less uncertainties in the background subtraction for the relevant spectra. In addition, all measured $g$-factor and $B(E2)$ data for the first ${2}^{+}$ and ${4}^{+}$ states in all stable even-$A$ Zn isotopes and the radioactive $^{62}\mathrm{Zn}$, are compared with new large-scale shell model calculations based on the most advanced effective interaction in the $\mathit{fpg}$-shell model space.

From transient field measurements on the Coulomb-excited first 2+ state of 40Ar ions, traversing Gd at the very high velocity of 19ν 0 (ν 0 = 1 137 c) a g-factor value of g = −0.1 (1) was deduced. The field was calibrated using data of 32S(2+) ions at comparable velocity. The g-factor result is in good agreement with shell-model predictions.

We have investigated the geometry as well as the equilibrium bond lengths for a number of possible structures of the Sb 4 cluster by the Hartree-Fock procedure. The tetrahedral structure is shown to exhibit higher stability than several planar structures studied. No stability could be found for a square in the singlet spin configuration, in keeping with considerations based on the Jahn-Teller theorem

Relative to the wellknowng-factor of56Fe(2 1 + ) at 0.847 MeV, theg-factor of the54Fe(2 1 + ) state at 1.408 MeV has been remeasured employing the technique of transient magnetic fields (TF) with the ions slowed down in ferromagnetic Gd host at initial velocities of 2.5 ν0. Coulomb excitation on beams of54,56Fe was accomplished with a Si target. The value obtained,g=1.05(17), is in excellent agreement with two previous results but disagrees with the value from a TF measurement where the ions passed through ferromagnetic Fe.

The $g$ factors and mean lifetimes of several short-lived low-lying states in ${}_{30}^{70}$${\mathrm{Zn}}_{40}$ have been measured using the techniques of projectile Coulomb excitation in inverse kinematics combined with transient magnetic fields and the Doppler-shift attenuation method. The present results have been interpreted within the framework of large-scale shell-model calculations that include the ${g}_{9/2}$ orbital.

International audience; The transient field strength for 76Ge ions, passing through iron and gadolinium layers at velocities ~Zv0, has been measured. Although a sizeable value has been obtained for Gd, a vanishing strength has been observed in Fe.

Lifetimes and g‐factors have been measured for short‐lived low‐lying states in 70Zn using the techniques of projectile Coulomb excitation in inverse kinematics combined with transient magnetic fields and the Doppler‐Shift‐Attenuation‐Method (DSAM). While the g(21+) value was redetermined and found to be consistent with the literature values, all other data are new. The main goal is a better understanding of the influence of the v(g9/2) orbital in this region of the nuclear chart.

It is shown that transient magnetic fields in Gd-host for20Ne ions at a mean velocity of 12.5v0(v0=c/137), considerably beyond the Bohr velocity of 1s electrons of Ne ions (v1s=10v0), are dominated by the Fermi contact field of these electrons. The first excited 2+-state of2Ne was used as probe. The derived value for the mean degree of polarization p1s=0.32(13), is surprisingly large, though still consistent with values obtained at lower velocities. Present calculations of spin exchange cross sections severely underestimate the observed polarization at this high velocity.

From measurements of transient magnetic fields (TF) on56Fe(21+) ions in Gd host there is evidence that beam induced attenuations of TF not only depend on the energy loss of the beam ions in the ferromagnet but also on the electron ns-orbitals of the probe ion contributing to the field. This has been demonstrated for 2s- and 3s-electron states of56Fe ions which are preferentially populated by setting the ion velocity to their respective orbital Bohr velocities.