Magnetic moments of the 10− isomeric states in 202Bi and 204Bi

The g-factors of the 10^? isomeric states in ²⁰²Bi and ²⁰⁴Bi have been measured by the method of in-beam TDPAD. The experimental values $\text{g = 0.243(14)}\text{for}{}^{202}\text{Bi}\text{and}\text{g = 0.236(23)}\text{for}{}^{204}\text{Bi}$ confirm the previously suggested shell-model configuration.     

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_{$\text{1}\text{2}$}.     

Collective excitations in the 123, 125I nuclei

The odd-proton nuclei ¹²³I and ¹²⁵I have been studied in the reactions ¹²¹Sb(α, 2n)¹²³I and ¹²³Sb(α, 2n)¹²⁵I, respectively. The level schemes, spin and parity assignments are based on results obtained from singles γ-ray spectra (E_α = 27 MeV) and excitation functions, from measurements of delayed γ-rays, γ-γ coincidences, internal conversion electrons and γ-ray angular distributions. High-spin positive- and negative-parity bands with energies up to 2948 keV and spins up to $\text{23}\text{2}$ in ¹²³I and with energies up to 3775 keV and spins up to $\text{27}\text{2}\text{in}{}^{125}\text{I}$ have been established. In the decay schemes of both nuclei two separated structures of levels have been observed. One group of levels shows a strong ΔJ = 2 quasirotational pattern predicted by the particle-vibration coupling model. The ΔJ = 1 sequence on a $\text{9}\text{2}$⁺ state is assigned as a rotational structure built on the axially symmetric deformed state $\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$. In ¹²³I a 28 ns isomer at 2660.0 keV has been found.     

A study of particle-vibration multiplets in 203Tl using the 205Tl(p,t)203Tl, 208Pb(p,t)206Pb and 206Pb(p,t)204Pb reactions

The ²⁰⁵Tl(p, t)²⁰³Tl reaction has been used at 26.2 MeV to obtain additional information on the particle-vibration multiplets in ²⁰³Tl. Enhancement factors for the L = 0 and L = 2 transitions to the lower excited states of ²⁰³Tl were well accounted for by using enhancement factors from the ²⁰⁶Pb(p, t)²⁰⁴Pb reaction and the wave functions from the intermediate coupling calculations of Covello and Sartoris. Additional data on the ²⁰⁸Pb(p, t)²⁰⁶Pb reaction at 26.2 MeV were used along with data at other energies to examine the energy dependence of the zero-range enhancement factors.     

Rotational bands in 195, 197Tl

High-spin states in ^{195, 197}Tl have been populated with (α, xn) reactions and studied by means of in-beam γ-ray and e^? spectroscopic methods. Complementary studies of the decay of ^{195, 197}Pb to ^{195, 197}Tl have been carried out. Several new features have been observed in these nuclei. The $\text{9}\text{2}{}^{\mathrm{?}}$ bands of ^{195, 197}T1. extended to $\text{27}\text{2}{}^{\mathrm{(?)}}$ and $\text{29}\text{2}{}^{\mathrm{(?)}}$, respectively, show a quenching of energy spacings between the $\text{23}\text{2}{}^{\mathrm{?}}$, $\text{25}\text{2}{}^{\mathrm{?}}$, $\text{27}\text{2}{}^{\mathrm{(?}}$ and $\text{29}\text{2}{}^{\mathrm{(?}}$ states. This has been interpreted as resulting from the coupling of a $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton to the ($\text{π}\text{h}{}^{\mathrm{?2}}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{8+,\; 10+}}$ configurations in the core nuclei ^{194, 196}Hg. Furthermore, positive-parity bands based on $\text{15}\text{2}{}^{\mathrm{+}}$ states were established up to the $\text{35}\text{2}{}^{\mathrm{(+)}}$ and $\text{29}\text{2}{}^{\mathrm{(+)}}$ states in ^{195, 197}Tl respectively. Probably these bands originate from the coupling of a h${}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton to a broken neutron pair. This pair consists of a rotation-aligned $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ neutron and a low-j neutron in the $\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ or $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ shell. It is known to constitute the 5^? bands in ^{194, 196}Hg.     

Magnetic moments in the backbending region of 158Dy

Yrast levels in the backbending region of ¹⁵⁸Dy were Coulomb excited with a 4.7 MeV/u ²⁰⁸Pb beam. Employing the transient field technique with a thin magnetized iron foil, the precessions of the angular correlations of decay γ-rays from levels up to spin I^π = 16⁺ were measured. The results show a clear reduction of the g-factor for states in the backbending region relative to that of the low-spin levels, thus demonstrating that the backbending in ¹⁵⁸Dy is mainly caused by the alignment of $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ neutrons. In a similar experiment, precession measurements on Coulomb excited low-spin levels of ¹⁶⁴Dy served to determine the static hyperfine field of Dy in Fe and the g-factor of the 6⁺ state in ¹⁶⁴Dy.     

Magnetic moments of high-spin states above the rotational band of 168Hf and 172Hf

The transient magnetic field IMPAC technique was used to measure the magnetic moments of high-spin states above the rotational band of ¹⁶⁸Hf and ¹⁷²Hf, populated in the reactions ^{156, 160}Gd(¹⁶O, 4n). The average g-factors of these prerotational feeding states were deduced to be 0.07 ± 0.04 and 0.14 ± 0.04 for ¹⁶⁸Hf and ¹⁷²Hf, respectively. These results are in agreement with a reduction of the collective g-factors due to a neutron phase transition.     

Cross sections and isomeric ratios in the photoproduction of 44Sc from heavier nuclei

The yields and isomeric yield ratios in the photoproduction of⁴⁴Sc from ⁴⁵Sc, ⁵⁵Mn, Fe, ⁵⁹Co and ⁷⁵As have been measured by activation methods in the energy region 100–800 MeV. Mean cross sections and isomeric cross-section ratios in the energy region 250–800 MeV have been deduced and the number of valence neutrons available for the (γ, n) reaction estimated. The experimental cross sections are compared both to cascade-evaporation calculations based upon the free-nucleon photopion cross sections and to cross sections calculated with a semi-empirical formula. The isomeric cross-section ratios are compared to calculations based on the statistical formalism by Huizenga and Vandenbosch together with cascade-evaporation theory.     

Nuclear reactions of 118Sn, 121Sb,and 127I with argon ions

Excitation functions have been measured for a number of (⁴⁰Ar, xn), (⁴⁰Ar, pxn), (⁴⁰Ar, 2pxn), and (⁴⁰Ar, 3pxn) reactions induced in ¹¹⁸Sn, ¹²¹Sb and ¹²⁷I over the lab. energy interval 150–280 MeV. Values of the total fusion cross section are obtained and J_crit is deduced. The value of J_crit increases with energy and becomes as large as 110–140?, in reasonable agreement with the yrast limit deduced from the ellipsoidal liquid drop model. The competition between proton and neutron emission from the compound nucleus is examined and $\text{Γ}{}_{\mathrm{<mtext>p</mtext>}}\text{Γ}{}_{\mathrm{<mtext>n</mtext>}}$ is found to increase rapidly with the number of emitted nucleons, thereby imposing severe limits on the production of very neutron deficient miclides via compound nuclear reactions. The effect of very high angular momentum on the excitation functions is examined.     

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.     

Studies of single-neutron holes in the transitional nuclei N = 83–89: The 142Ce(d,t)141Ce and 142Ce(3He, α)141Ce pick-up reactions

The level structure of ¹⁴¹Ce up to 3.7 MeV excitation energy has been investigated by the (d, t) and (³He, α) reactions using 17 MeV deuteron and 24 MeV ³He beams respectively. The angular distributions have been analyzed with standard DWBA calculations and spectroscopic factors are deduced. The experimental information is compared to unified model calculations involving both one-particle and two-particle one-hole configurations with quadrupole and octupole vibrations of the underlying N = 82 and N = 84 core.     

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.     

In-beam study of the odd-odd nuclei 134La and 136La

The level schemes of the nuclei ^134,136La have been studied by means of in-beam γ-ray spectroscopic methods following the (α, 3n) and (p, 3n) reactions. New isomers with half-lives of 29 ± 5 μs and 17 ± 4 ns have been discovered in ¹³⁴La and ¹³⁶La, respectively. Low-lying levels and isomers in ^134,136La have been interpreted as members of multiplets having $\text{(π}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{v}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{), (π}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{v}\text{s}{}^{\mathrm{?1}}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}\text{and}\text{(π}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{v}\text{h}{}^{\mathrm{?1}}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}$ configurations.     

In-beam γ-ray studies of complex band structures and of isomeric states in 152, 153Dy nuclei

The high-spin level structures of ¹⁵²Dy and ¹⁵³Dy were studied experimentally with ^{154, 155}Gd(α xnγ) in-beam reactions, and for ¹⁵²Dy also with ${}^{\mathrm{144,\; 146}}\text{Nd}\text{(}{}^{12}\text{C, x}\text{n}\text{γ)}$ reactions. The experiments included measurements of singles γ-ray and conversion-electron spectra, γ-ray angular distributions and E_γ-t and E_γ-E_γ-t coincidences. A multiplicity filter set-up was used to study the feeding and decay of isomeric states in ¹⁵²Dy. In ¹⁵²Dy about twenty so far unknown levels were found, including two high-spin isomeric states with $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{≈ 60}\text{and}\text{≈ 13}\text{ns}$ at excitation energies E_x ≈ 5.04 and 6.08 MeV, respectively. These states are compared with recent calculations on yrast traps. The level scheme of ¹⁵³Dy contains 28 levels up to E_x = 4.1 MeV and $\text{J}{}^{\mathrm{\pi }}\text{= (}\text{37}\text{2}{}^{\mathrm{+}}\text{)}$. Band structures in both nuclei are discussed in comparison with other N = 86 and N = 87 isotones.     

Transition probabilities in the doubly odd nuclei 176Lu and 182Ta

The depopulation of isomeric states in ¹⁷⁶Lu and ¹⁸²Ta was studied in the (n, γ) reaction by means of delayed γ-γ coincidence measurements with NaI(Tl) and Ge(Li) detectors. The following half-lives, unknown so far, have been obtained for ¹⁷⁶Lu: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(198.0}\text{keV}\text{) = 35.0 ± 1.0}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(638.8}\text{keV}\text{) = 8.0±1.0}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(662.1}\text{keV}\text{) = 6.3±0.5}\text{ns}$; and for ¹⁸²Ta: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(270.4}\text{keV}\text{) = 1.2 ± 0.2}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(402.6}\text{keV}\text{) = 1.00 ± 0.05}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(443.6}\text{keV}\text{) = 2.2 ± 0.2}\text{ns}$. The existence of the isomeric level at 443.6 keV in ¹⁸²Ta was confirmed. Weisskopf hindrance factors have been deduced for the K- and Ω-forbidden transitions. The K-allowed transitions are considered in terms of the Nilsson model taking into account pairing correlations. The experimental results for the transitions de-exciting the 270.4 keV level in ¹⁸²Ta agree with earlier model predictions including band mixing effects. The influence of the pairing effect on K-allowed E1 transitions in doubly odd nuclei is demonstrated.     

Break-up of 6Li and 7Li on tin and nickel nuclei

The break-up of the stable lithium nuclei on ⁵⁸Ni and ¹¹⁸Sn has been investigated in the bombarding energy range 12–24 MeV. The emerging α-particles have been analysed showing that the cross sections peak at the angle of grazing collisions. Inspection of the present data suggests the conclusion that several different reaction mechanisms contribute to the continuous spectrum of the α-particles.     

Observation of isomeric states and band structures in 107Cd

The odd-mass nucleus ¹⁰⁷Cd was investigated in the reactions ${}^{105}\text{Pd}\text{(α, 2}\text{n}\text{)}{}^{107}\text{Cd}\text{,}{}^{107}\text{Ag}\text{(d, 2}\text{n}\text{)}{}^{107}\text{Cd and}{}^{107}\text{Ag}\text{(}\text{p, n}\text{)}{}^{107}\text{Cd}$. The constructed level scheme is based on results, obtained from singles γ-ray spectra and excitation functions, from the measurements of delayed γ-rays, of γ-γ coincidences, of internal conversion electrons and of γ-ray angular distributions. Two new isomers were observed. The first one, interpreted as the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ neutron state at 845.6 keV has a half-life of 67 ± 6 ns. This isomeric state is populated by a strong E2 cascade. Bands built on the other intrinsic states with spins and parities $\text{5}\text{2}{}^{\mathrm{+}}$ and $\text{7}\text{2}{}^{\mathrm{+}}$ are not strongly populated. For the second isomeric state at an excitation energy of 2679 keV a half-life of 55±4 ns was determined. This isomer is probably a three-quasiparticle state. Its configuration can be proposed as $\text{[π(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}{}_{\mathrm{8+}}\text{ν(}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^1\text{]}{}_{\mathrm{<mtext>21</mtext><mtext>2</mtext>}}{}^{\mathrm{+}}$.     

Gamma transitions between low-lying levels in 119Sn

We have carried out measurements on the decay of ¹¹⁹In isomers and the ¹¹⁸Sn(n, γ) reaction to supplement Coulomb excitation measurements on ¹¹⁹Sn. In addition to the 311.39 keV isomeric transition in ¹¹⁹In, we observed 13 γ-rays in ¹¹⁹Sn from the decay of the 2 min and 18 min ¹¹⁹In isomers. These γ-rays have been incorporated into a level scheme of ¹¹⁹Sn with levels at 0, 23.867, 89.54, 787.01, 920.5, 921.4, 1089.5, 1187.76, 1249.67, 1304.44 and 1354 keV. Conclusive evidence for the existence of a 920.5–921.4 keV, $\text{3}\text{2}{}^{\mathrm{+}}\text{-}\text{5}\text{2}{}^{\mathrm{+}}$ level doublet was obtained from capture γ-ray measurements of resonance energy neutrons.     

Photonuclear reactions in medium weight nuclei 51V, 55Mn and Cu

New results on the photospallation of the medium weight nuclei ⁵¹V, ⁵⁵Mn and Cu at maximum bremsstrahlung energy between 2 and 5 GeV are presented. The yields of residual nuclei were measured by the activation method using a Ge(Li) detector. The results are analyzed with the empirical Rudstam formula and compared with data obtained in lower energy photon and proton induced reactions.