g-factors of high-spin isomeric states in 216Ra

The g-factors of two isomeric states at E_x = 3763 and 5170 keV in ²¹⁶Ra have been measured to be 0.51 ± 0.03 and 0.63 ± 0.06, respectively, with a TDPAD method. Spin and parity assignments of 19^? for the 3763 keV state and 25^? or 24⁺ for the 5170 keV state are consistent with the measured g-factors. Proposed configurations for the 19^? and 25^? assignments are of the same type as those predicted by a deformed independent-particle model for ²¹⁴Rn, which is an isotone of ²¹⁶Ra.     

Average g-factors for high-spin states in 78Kr

Inverse reactions of ^{63, 65}Cu beams on ^{18, 16}O targets have been used to populate states of ⁷⁸Kr by fusion-evaporation reactions. The excited nuclei recoiled at high velocity v/c ≈ 7 % through a polarized iron (⁵⁴Fe) layer and were stopped in a copper layer. During the period in iron, 0.05–0.65 ps, the nuclei were subjected to the intense transient magnetic field (initially ～ 3500 T). The resulting precession of the high-spin nuclear states populated during this time was determined by measuring the time integral rotation angle of the discrete γ-ray transitions at low spin.The average g-factor at low spin 2 ≦ J ≦ 8 compared to that at higher spin 8 ≦ J ≦ 12 in ⁷⁸Kr was found to be identical within the experimental uncertainties of ～ 15 %. This result implies that either there are no rotational alignment effects at the backbend in ⁷⁸Kr or more plausibly, proton (g ≈ 1) and neutron (g ≈ 0) aligned bands are equally competitive and both populated in the reaction. It is then likely that the resulting g-factor represents an average over many populated proton and neutron aligned bands.     

Static quadrupole moments of the first excited states of 200Hg and 202Hg

The static quadrupole moments Q_2⁺ and B(E2; 0⁺ → 2⁺) values of the 2⁺ first excited states of ²⁰⁰Hg and ²⁰²Hg have been determined using the reorientation effect in Coulomb excitation. An annular silicon surface-barrier detector was used to detect backscattered ⁴He, ¹²C and ¹⁶O projectiles. It is found that for ²⁰⁰Hg, Q_2⁺ = +1.07 ± 0.19 e · b(+0.98 ± 0.19 e · b) for destructive (constructive) interference from the 2^+′ state, and B(E2; 0⁺ → 2⁺) = 0.853 ± 0.007 e² · b². For ²⁰²Hg, we find Q_2⁺ = +1.01 ± 0.13 e · b (+0.87 ± 0.13 e · b) and B(E2; 0⁺ → 2⁺) = 0.605 ± 0.005 e² · b². The Q_2⁺ value obtained for ²⁰⁰Hg is in agreement with previous work, but that for ²⁰²Hg is not. The results obtained are compared with the predictions of various nuclear models, and the mass dependence of Q_2⁺ in the region 182 ≦ A ≦ 206 is examined.     

Magnetic moments of the 12+ isomeric states in 194, 196, 198Pb

The g-factor of the 12⁺ isomeric state in lead isotopes with A = 194, 196, 198 was measured using the time-differential perturbed angular distribution method (TDPAD). The values obtained are respectively g(194) = ?0.158(6); g(196) = ?0.157(7); g(198) = ?0.144(11). A more precise determination of the 12⁺ level half-life is also made. The g-factprs of these nuclear states, which are described with v(i_{$\text{13}\text{2}$})^?2 as the main configuration, are surprisingly constant over a large mass range (between A = 206 and 194). A core polarization analysis explains this trend: the polarization induced on neutrons in i_{$\text{13}\text{2}$} orbit decreases with the mass number A (blocking effect), but a compensation is provided by the other spin-orbit partners f_{$\text{7}\text{2}$}-f_{$\text{5}\text{2}$} and P_{$\text{3}\text{2}$}-P_{$\text{1}\text{2}$}.     

Study of orientation transfer by collisions of the second kind between 198Hg and 199Hg atoms

A double resonance experiment is used to detect the collisional transfer of orientation from an optically oriented ¹⁹⁸Hg (6³P₁) atom to the hyperfine levels $\text{(6}{}^3\text{P}{}_1\text{; F =}\text{1}\text{2}\text{, F =}\text{3}\text{2}\text{)}$ of a ¹⁹⁹Hg atom. The reaction of transfer is assumed to be ¹⁹⁸Hg (6³P₁) + ¹⁹⁹Hg (6¹S₀) → ¹⁹⁸Hg (6¹S₀) + ¹⁹⁹Hg (6³P₁).The theory of such a process is summarized, the experimental set-up described and the double resonance signals compared with those predicted by the theory.     

Continuous gamma radiation feeding high-spin isomers in 148, 149, 151, 152Dy and 147Gd

The energy, multipolarity and multiplicity spectra of the continuum gamma radiation feeding high-spin isomers in ^{148, 149, 151, 152}Dy and ¹⁴⁷Gd have been measured at several bombarding energies. The final nuclei were selected via a delayed coincidence technique while the use of a NaI(Tl) Compton shielded crystal allowed the primary gamma-ray spectra to be generated reliably from the observed spectra.It was found that: (i) the energy of both the gamma-ray statistical cascade and the neutron cascade increases with increasing excitation energy, the latter much more rapidly than expected; (ii) the multiplicity of gamma-ray cascades, in which a statistical transition was detected, is generally lower than that of the average cascade; (iii) stretched E2 spin-correlated transitions occur above $\text{J? 39}\text{h}\text{?}\text{in}{}^{152}\text{Dy}$ and above $\text{～ 50.5}\text{h}\text{?}\text{in}{}^{147}\text{Gd}$, indicating the onset of collectivity at these spins — in addition, a region of predominantly dipole emitting states is located below $\text{T? 44}\text{h}\text{?}\text{in}{}^{147}\text{Gd}$; (iv) effective moments of inertia derived from the bump edge are 50–100% larger than those deduced from the density of stretched E2 transitions in the bump; (v) in ^149,151Dy the bump edge is very sharp but no multiplicity features are observed; (vi) although the four Dy isotopes were populated at approximately the same excitation energy, they display considerable differences in their continuum properties.Probable interpretations of these observations are discussed, in particular we have suggested that several of the observed effects are consistent with the possible presence of high-K collective bands above the yrast line.     

Possible bubble nuclei -36Ar and 200Hg

The question of bubble configurations for ³⁶Ar and ²⁰⁰Hg is studied by Hartree Fock calculations using the density dependent force G-0. By imposing a constraint the solutions can be studied as a function of bubble deformation. Pairing is included in a self consistent manner via a B.C.S. calculation. Factors leading to bubble versus uniform distribution are discussed.     

Yrast and high-spin states in 22Ne

High-spin states in ²²Ne have been investigated by the reactions ¹¹B(¹³C, d)²²Ne and ¹³(¹¹B, d)²²Ne up to $\text{E}{}^1\text{～- 19}\text{MeV}$. Yrast states were observed at 11.02 MeV (8⁺) and 15.46 MeV (10⁺) excitation energy. A backbending in ²²Ne is observed around spin 8⁺. The location of high-spin states I ≦ 10 is discussed in terms of the rotational band structure, Strutinsky-type calculations, and pure shell-model predictions.     

Isomers and high-spin states in 205At

The properties of high-spin states in ²⁰⁵At have been investigated to $\text{J ?}\text{37}\text{2}$ and an excitation energy of > 4.0 MeV. The properties of the $\text{29}\text{2}$⁺ isomer at 2340 keV have been established and those of the $\text{25}\text{2}$⁺ isomer at 2063 keV have been further investigated. In the present study the mean lives of these isomers have been determined as 11.2±0.2μs and 98±2 ns respectively. The M2 branch of the $\text{13}\text{2}$⁺ state at 970 keV to the $\text{9}\text{2}$⁺ ground state has been measured. This decay is attributed to a proton single-particle $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}\text{→}\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ transition. The trend of excitation energies of a number of proton excitations in the odd-mass nuclei from ²¹¹At to ²⁰¹At has been compared to the corepolarization model and the average $\text{ν}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{π}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ interaction energy has been deduced. Comments are made upon probable configurations for many of the levels.     

A high-spin isomer in 204Bi

By making use of heavy-ion and α-particle induced reactions an isomeric state has been found in ²⁰⁴Bi, with a half-life of $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 1.07 ± 0.03}\text{ms}$ and the quantum characteristics I^π = 16⁺. The four-quasiparticle configuration $\text{ν(}\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}\text{ν(}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}{}^1\text{π(}\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^1$ has been ascribed to this state.     

Short-lived isomers in 211Rn and 210Rn

The following mean lives of excited states in ²¹¹Rn and ²¹⁰Rn have been measured: ²¹¹Rn: 8169 + Δ' keV, (τ = 3.3(3) ns), 7400 + Δ' keV (2,1(5) ns), 6101 + Δ' (41(2) ns), 5247 + Δ keV (5(2) ns), 3244 + Δ keV (3.9(8) ns), 2651 + Δ keV (9.6(4) ns); ²¹⁰Rn: 8555 + Δ keV (2.6(3) ns), 4994 + Δ keV (19(1) ns), 1665 keV (15.0(15) ns). Some theoretical implications of these measurements for the structure of ²¹¹Rn and ²¹⁰Rn are discussed.     

Spins of levels in 194Pt

Selected cascades in the level scheme of the ¹⁹⁴Pt nucleus have been studied by the γ-γ directional correlation method and the spins of the 924, 1513, 1623, 1672 and 1798 keV levels determined to be 3, 2, 2, 2 and 1 respectively. The multipole mixing ratios of the 301, 594, 1184 and 1295 keV γ-transitions have been determined and a number of B(E2) ratios are compared with theory.     

The g-factors of short-lived isomeric states in 108Ag and 110Ag

Short-lived isomeric states in ¹⁰⁸Ag and ¹¹⁰Ag were populated by means of (p, n) and (d, p) reactions. The nuclear g-factors of these states were determined with the pulsed beam DPAD method to be $\text{g(}{}^{108}\text{Ag}\text{; 215}\text{keV}\text{) = 1.294(6)}\text{and}\text{g(}{}^{110}\text{Ag}\text{; 119}\text{keV}\text{) = 1.277(15)}$. The results indicate a spin and parity I^π = 2⁺ for ¹⁰⁸Ag and I^π = 3⁺ for ¹¹⁰Ag.     

Transient field measurements of g-factors for 28Si and 30Si

Transient field precession measurements have been performed on the first excited J^π = 2⁺ states of ²⁸Si and ³⁰Si with the IMPAC technique on recoil in magnetized iron. The results were analyzed with empirically adjusted Lindhard-Winther predictions. This yields g-factors of $\text{g = +0.56 ± 0.09}\text{and}\text{g = +0.56 ± 0.16}\text{for}{}^{28}\text{Si and}{}^{30}\text{Si}$, respectively. In the present cases the influence of static hyperfine fields is negligible due to the very short mean lives for ²⁸Si and ³⁰Si of 0.68 and 0.35 ps, respectively. The results are compared with theoretical calculations. Previous results for ²⁶Mg(2₁⁺) were reanalyzed with the more recent lifetime of τ_m = 0.72 ± 0.03 ps. The value of the g-factor becomes g = +0.82 ± 0.16.     

The g-factor of the 6+ state in 50Ti

The rotation of the angular distribution pattern of the 524 keV γ-radiation from the 6⁺, 3200 keV state in ⁵⁰Ti was measured in an external magnetic field using the ⁴⁸Ca(α, 2n) reaction. The IPAD method was applied. From the experimental precession angle, the value of the g-factor, g = 1.57 ± 0.17, has been derived.     

Structure of high-spin states in 143Pm

High-spin states of ¹⁴³Pm have been studied in the reactions ¹⁴¹Pr(α, 2n)¹⁴³Pm and ¹⁴³Nd(d, 2n)¹⁴³Pm by means of in-beam spectroscopy. The level scheme, spin and parity assignments are based on results obtained from singles γ-ray spectra, conversion electron spectra, prompt and delayed γ-γ coincidences, γ-ray angular distribution and linear polarization measurements. Positive- and negative-parity states with energies up to 4580 keV and spins up to $\text{25}\text{2}$ have been established including 22 new levels. For two nanosecond isomeric states the nuclear spin precession in an external magnetic field was observed providing the following g-factors:

$\text{g(}\text{11?}\text{2}\text{, 959.7 keV)=1.14(9), g(}\text{15+}\text{2}\text{, 1898.3 keV)=1.00(7).}$

The experimental results are well understood by calculations which have been performed in the framework of the shell model (for positive-parity states of 11 valence protons above a Z = 50, N = 82 core) and of the cluster-vibration model (for 3 holes in a Z = 64, N = 82 core). In the case of positive-parity states no evidence for particle-core coupling could be found, while the negative-parity states could qualitatively be understood within the particle-core coupling picture.     

Spin-parity assignments to high-spin states of 41K and 41Ca

Yrast states of ⁴¹K and ⁴¹Ca have been investigated with the ²⁶Mg(¹⁸O, p2nγ)⁴¹K and ²⁶Mg(¹⁸O, 3nγ)⁴¹Ca reactions at a beam energy of 34 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}$, $\text{11}\text{2}{}^{\mathrm{+}}$, $\text{11}\text{2}{}^{\mathrm{?}}$, $\text{13}\text{2}{}^{\mathrm{+}}$, $\text{15}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$ to the ⁴¹K levels at E_x = 1.68, 2.53, 2.76, 2.77, 4.27 and 4.98 MeV and of $\text{9}\text{2}{}^{\mathrm{+}}\text{,}\text{11}\text{2}{}^{\mathrm{+}}\text{and}\text{15}\text{2}{}^{\mathrm{+}}$to the ⁴¹Ca levels at E_x = 3.20, 3.37 and 3.83 MeV, respectively, have been obtained. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The main features of the ⁴¹K and ⁴¹Ca level and decay schemes are reproduced in a 2p-1h and 3p-2h shell-model calculation.     

1+ state and effective g-factor

The effects of nuclear field r²(Y₂σ₁)_1υ on magnetic properties of single-particle states in odd-A nuclei (^208±1Pb) are considered. The coupling constant associated with this type of field is estimated by an argument that realtes it to the coupling constant for the field (γ₀σ₁)_1υ. The effects of including the r²(Y₂σ₁)_1υ field on the M1 moments and transitions are estimated.     

Shape coexistence and high-spin states in 28Si

The spectrum of ²⁸Si is investigated within the cranked Nilsson-Strutinsky model with all kinds of many-particle-many-hole excitations accounted for. Calculated excitation energies and quadropole moments are compared with experimental data. The recently observed backbend from 8⁺ to 10⁺ is suggested to be caused by the crossing of the oblate ground band with a prolate or slightly triaxial band having one proton and one neutron excited to the fp shell.