A. M. Kleinfeld

Lifetime measurements of states in 41Ca and 41K

Abstract Measurements of the γ-ray decay of states in 41Ca and 41K populated in the reactions 27Al(16O, pn) and 27Al(16O, 2p) have been performed. Using the recoil distance Doppler shift method, mean lifetimes were determined for states in 41 Ca at 3370 keV (28 ± 5 ps ), 3830 keV (4.4 ± 0.3 ns ) and 3915 keV (2.6 ± 0.8 ps ), and in 41 K at 2528 keV (230 ± 12 ps ), 2761 keV (1.3. +1.1 −0.6 ps ), 2774 keV (74 ± 8 ps ) and 4983 keV (101 ± 5 ps ) . The 3370 and 3830 keV states in 41Ca are suggested to be J π = 11 2 + and 15 2 + , respectively, having predominantly 2p–1h configurations. These suggestions contradict a recent interpretation of these states as being members of a strongly deformed K = 3 2 − rotational band.

Reorientation effect measurements of even mercury isotopes

Reorientation effect and multiple Coulomb excitation measurements have been performed for198, 200, 202, 1204Hg. By measuring particle spectra after Coulomb excitation of an enriched198Hg target with4He and16O beams, a positive quadrupole moment of Q2 = 0.66±0.18 eb (for negative interference) or Q2=0.80±0.18 eb (for positive interference) andB(E2,0→2)=0.991±0.006 e2b2 were obtained. All otherB(E2) values and quadrupole moments were determined relative to these numbers from preciseγ-ray yields obtained from Coulomb excitation of a frozennatHg target with4He and16O projectiles. Oblate shapes of all Hg isotopes were found. The data have been interpreted in terms of triaxial rotation and anharmonic vibrations.

Gamma radiation following heavy ion reactions

Abstract The gamma radiation produced by bombarding 27 A1 and 28 Si targets with 25–50 MeV 16 O ions was measured in order to study the formation and decay of the highly excited compound nuclei 43 Sc and 44 Ti. The relative population of the evaporation residues is fairly well reproduced by a statistical theory describing the successive emission of 1–3 light fragments. From the measured branching ratio between proton and α-particle emission, the moment of inertia parameter of the level density is found to be close to the rigid body value. The influence of heavy ion optical transmission factors, level density parameters and γ-ray decay widths of continuum states is investigated.

Hyperfine interactions of Pt nuclei recoiling into helium and vacuum

Abstract Perturbed γ-ray angular distributions were measured for Coulomb excited 194, 195, 196, 198 Pt recoiling into He and vacuum at v / c = 0.010. Calibration of the hyperfine field yielded the following g -factors: g(240 keV , 5 2 − ; 195 Pt ) = 0.22 ± 0.04 ; g (407 keV, 2 + ; 198 Pt) = 0.29 ± 0.06. Ratios of g -factors were also obtained directly from the perturbation parameters of the even nuclei and a new behaviour of the hyperfine interaction at low gas pressures was observed. The hyperfine field and its atomic structure dependence is compared to previous results.

Reorientation effect measurements in 124Te, 126Te and 128Te

Abstract Coulomb excitation probabilities of the first 2 + states of 124 Te, 126 Te and 128 Te have been determined. The measurement was performed by resolving the inelastically and elastically backward scattered 4 He and 16 O projectiles using an annular surface barrier detector. Quadrupole moments ( Q 2+ ) as well as the B (E2, 0 + → 2 + ) values were extracted by analyzing the excitation probabilities with the Winther-de Boer multiple Coulomb excitation program. The Q 2 deduced for the positive sign of the 2 + interference term are −0.41 ± 0.08 e · b, −0.144 ± 0.11 e · b and −0.12 ± 0.09 e · b for 124 Te, 126 Te and 128 Te, respectively.

Reorientation effect and multiple coulomb excitation measurements of 134Ba

Abstract Measurements of five E2 matrix elements involving the first four levels in 134 Ba have been performed using Coulomb excitation. A small and negative quadrupole moment of Q 2 + = − 0.34± 0.16 e · b or − 0.13± 0.16 e · b was determined, depending upon the sign of P 4 . It is found that the interacting boson model provides a good description of 134 Ba for either sign of P 4 . This is in contrast to many other models which predict P 4

The reorientation effect in 110Cd and 114Cd

Abstract New detailed measurements of the reorientation effect in the first 2 + state of 110 Cd and 114 Cd were carried out using back-scattered 4 He and 16 O ions. They yield Q 2 + = − 0.28±0.09 e · b with B (E2; 0 → 2) = 0.513±0.005 e 2 · b 2 , or Q 2 + = − 0.03±0.09 e · b with B (E2; 0 → 2) = 0.512±0.005 e 2 · b 2 for 114 Cd depending on the sign of the interference term. The results for 110 Cd are Q 2 + = −(0.42 or 0.21)±0.10 e · b with B (E2; 0 → 2) = 0.432±0.006 e 2 · b 2 . The deduced Q 2 + for 114 Cd is approximately half of the rotational-model value.

Reorientation effect measurements of 122Te and 130Te

Abstract Coulomb excitation probabilities of the first 2 + states of 122Te and 130Te have been determined. The measurement was performed by resolving the inelastically and elastically scattered 4He and 16O projectiles using eight surface barrier detectors between 44° and 173°. Quadrupole moments Q2+ as well as B(E2, 0+ → 2+) values were deduced. The Q2+ found for the positive sign of the 22+ interference term are −0.46±0.05 e · b and −0.15±0.10 e · b for 122Te and 130Te respectively.

Reorientation effect measurements and multiple coulomb excitation in102Ru

The quadrupole moment of the first 2+ state in102Ru and fourB(E2) values have been measured by means of Coulomb excitation. The results are:Q2+=−0.68(8)eb;B(E2, 01/+→21/+)=0.617(5)e2b2;B(E2, 01+→22/+)=0.013 (2)e2b2;B(E2, 21/+→22/+)= 0.07(1)e2b2;B(E2, 21+→41+)=0.30(6)e2b2. The results are discussed within the frame of the Interacting Boson Approximation.

Oblate shapes of200, 202, 204Hg

Measurements of the reorientation effect for the first excited 2+ states in200, 202, 204Hg were performed by exploiting the dependence of theγ-ray yield on Q2+ for different projectiles. For200Hg, a positive quadrupole moment of Q2=0.96±0.11 eb (for negative interference) or Q2=1.11±0.11 eb (for positive interference) was determined indicating an oblate shape. Small positive Q2 values were also found for202Hg and204Hg. Nine B(E2) values for excitation of the 2+, 2+′ and 4+ states in196–204Hg measured.