The γ-decay of the g92 analogue state in 59Cu

An investigation of the γ-decay of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ analogue state in ⁵⁹Cu has been performed using the ⁵⁸Ni(p, γ)⁵⁹Cu reaction. The (p, γ) excitation function has been taken in the range E_p = 3450–3650 keV. The decay schemes of the (p, γ) resonances at E_p = 3483, 3532 and 3547 keV, measured with Ge(Li) detectors, lead to eight new levels in ⁵⁹Cu with excitation energies between 1.8 and 4.7 MeV and to spin assignments of several states. The spins of the first two resonances are found to be ($\text{1}\text{2}$, $\text{3}\text{2}$) and ($\text{5}\text{2}$). The spin of the E_p = 3547 keV resonan is, from angular distributions, uniquely determined to be $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}$ and this state is found to be the unfragmented analogue state of the $\text{E}{}^1\text{= 3.062}\text{MeV}$, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}$ parent state in ⁵⁹Ni. The measured complete decay scheme of this resonance shows that its isovector M1 decay is in disagreement with all existing theoretical predictions.     

Competition cusps in (α, γ) reactions

Absolute cross sections are presented for the reactions ³⁷Cl(α, γ)⁴¹K for 2.90 MeV ≦ E^lab_α ≦ 5.23 MeV, ${}^{62}\text{Ni}\text{(α, γ)}{}^{66}\text{Zn}\text{for}\text{5.07}\text{MeV}\text{≦ E}{}_{\mathrm{\alpha }}{}^{\mathrm{?2}}\text{lab}\text{≦ 8.64}\text{MeV}\text{,}{}^{62}\text{Ni}\text{(α,}\text{n}\text{)}{}^{65}\text{Zn}$ for energies near the (α, n₀) threshold at $\text{E}{}_{\mathrm{\alpha }}{}^{\mathrm{<mtext>lab</mtext>}}\text{= 6.90}\text{MeV up to}\text{8.76}\text{MeV}\text{,}{}^{64}\text{Ni}\text{(α, γ)}{}^{68}\text{Zn for}\text{4.50 ≦ E}{}_{\mathrm{\alpha }}{}^{\mathrm{<mtext>lab</mtext>}}\text{≦ 7.45}\text{MeV}$, and for ⁶⁴Ni(α, n)⁶⁷N from E_α^lab = 5.30 MeV up to E_α = 7.45 MeV. Substantial competition cusps were observed in the excitation function for all three (α, γ) reactions. The data were found to be in reasonable agreement with the predictions of the current versions of global Hauser-Feshbach models used in nucleosynthesis calculations. Including width fluctuation corrections and realistic neutron strength functions generally improves the ability of the models to predict the depth of the (α, γ) competition cusps; the depths of the predicted (α,γ) cusps are insensitive to the degree of isospin mixing. Taken together with studies of competition effects in proton-induced reactions, the present data confirm the importance of width fluctuation and strength function effects, and indicate essentially complete isospin mixing between T^< and T^> states in the compound nucleus.     

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.     

High-spin states of 39K and 42Ca

High-spin states of ³⁹K and ⁴²Ca have been investigated with the ²⁸Si(¹⁶O, αpγ)³⁹K and ²⁸Si(¹⁶O, 2pγ)⁴²Ca reactions at a beam energy of 45 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. High-spin states of ³⁹K at E_x = 7.14,7.78and8.03 and of ⁴²Ca at E_x = 7.75MeV are established. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{=}\text{11}\text{2}{}^{\mathrm{?}}\text{,}\text{13}\text{2}{}^{\mathrm{?}}\text{,}\text{15}\text{2}{}^{\mathrm{+}}\text{,}\text{15}\text{2}{}^{\mathrm{?}}\text{,}\text{17}\text{2}{}^{\mathrm{+}}\text{and}\text{19}\text{2}{}^{\mathrm{?}}$ to the ³⁹K levels at E_x = 5.35, 5.72, 6.48, 7.14, 7.78 and 8.03 MeV and of 6^?, 7^?, 8^?, 9^? and(8, 10)^? to the ⁴²Ca levels at E_x = 5.49, 6.15, 6.41, 6.55 and 7.37 MeV, respectively, have been obtained. Further spin-parity restrictions, lifetime limits, excitation energies, branching ratios and multipole mixing ratios are reported. Discrepancies with previous J^π assignments are discussed in detail.     

Spectroscopy of 41K by thermal neutron capture in 40K

The γ-ray spectrum emitted after thermal neutron capture in ⁴⁰K has been studied at the ILL high flux reactor with curved crystal Bragg, pair and Ge(Li) spectometers. 585 transitions were assigned to the reaction ⁴⁰K(n, γ)⁴¹K and 490 of them were placed into a ⁴¹K level scheme; 68 new states are proposed. On the basis of γ-ray branches to states with established spin and parity, many new spin-parity assignments were made. The level energies up to 4 MeV were measured with a precision of 8–50 eV relative to the 411.8 keV ¹⁹⁸Au standard, those above 4 MeV with a precision of 50–100 eV. The spin of the capture state was found to be $\text{I =}\text{7}\text{2}$; the neutron binding energy was determined to E_B = 10095.25(10) keV. The level density of $\text{I}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{\pm }}\text{,}\text{7}\text{2}{}^{\mathrm{\pm }}\text{,}\text{9}\text{2}{}^{\mathrm{\pm }}$ states was analyzed in terms of the constant-temperature Fermi gas model. It was shown that in this spin window the level scheme is almost complete up to an excitation energy of 5 MeV.     

The excited states of 27Al

The γ-decay of 60 and the strengths of 51 ²⁶Mg(p, γ)²⁷Al resonances were studied for E_p < 2.20 MeV. The energies of 32 and the γ-decay of 54 bound levels were determined. Spin and parity assignments $\text{J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}\text{,}\text{5}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{and}\text{3}\text{2}{}^{\mathrm{+}}$ were made to the bound states at E_x = 4.81, 5.44, 6.61, 6.78, 7.68 and 7.86 MeV, respectively. Spin assignments $\text{J =}\text{5}\text{2}$and $\text{3}\text{2}$ were made to the bound levels at Einx = 5.55 and 6.08 MeV, respectively. For other levels spin and parity limitations were set. Lifetimes or lifetime upper limits of 19 bound levels were measured by means of the DSA technique. The spins and/or parities of 15 resonances were unambiguously determined from γ-ray angular distributions and strengths.     

The decay properties of 3.25 min 169Hf and 2.05 min 167Hf

The decays of 3.25 min ¹⁶⁹Hf and 2.05 min ¹⁶⁷Hf have been studied with high-resolution Ge(Li) and Si(Li) detectors. The total decay energy of ¹⁶⁹Hf determined from our experimental $\text{K}\text{β}{}^{\mathrm{+}}$ ratio is 3.29^+0.05_?0.13 MeV. The allowed unhindered character of the main β-branches in the decay of both isotopes allows unique Nilsson model assignments.     

Structure of 57Fe studied with 56Fe(d, p)57Fe reactions

${}^{56}\text{Fe}\text{(}\text{d}\text{, p}\text{)}{}^{57}\text{Fe}$ reactions have been studied with 10 MeV vector polarized deuterons over the angular range 15° ≦ θ_p ≦ 80°. Angular distributions of the vector analysing power and the differential cross section have been measured for reactions leading to levels in ⁵⁷Fe. Distorted wave Born approximation calculations are compared to the measurements. The observed j-dependence of the vector analysing power results in eighteen new spin-parity assignments for levels in ⁵⁷Fe. Spectroscopic factors are extracted from the differential cross-section measurements. The results are compared to the predictions of the single-particle shell model and to models including collective structure.     

High-spin yrast levels of 38Ar

High-spin states of ³⁸Ar have been studied with the ³⁵Cl(α, pγ)³⁸Ar reaction at E_α = 18 MeV and with the ²⁴Mg(¹⁶O, 2pγ)³⁸Ar reaction at $\text{E(}{}^{16}\text{O}\text{) = 38}\text{and}\text{45}\text{MeV}$. The ³⁸Ar level scheme is obtained with the former reaction from a proton-γ coincidence measurement. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization experiments have been performed with a Ge(Li)-Na(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{= 7}{}^{\mathrm{?}}\text{, 7}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{, 7}{}^{\mathrm{?}}\text{, 9}{}^{\mathrm{?}}\text{and}\text{11}{}^{\mathrm{?}}$to the ³⁸Ar levels at E_x = 7.51, 8.08, 8.57, 8.97, 10.17 and 11.61 MeV, respectively, are obtained. The 8.57 MeV, 8⁺ level has a mean life below 0.8 ps. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The experimental results are compared with shell-model calculations.     

Coulomb excitation and lifetime measurements of the 21+ states in 76, 82, 84Kr

A mean lifetime of τ = 35 ± 3 ps of the 2⁺₁ state in ⁷⁶Kr has been measured with the recoil distance method via the reaction ⁶³Cu(¹⁹F, α2n)⁷⁶Kr. The B(E2; 0⁺₁ → 2⁺₁) values and lifetimes of the 2⁺₁ states in ^{82, 84}Kr have been measured via Coulomb excitation using the 1.4 MeV/A UNILAC krypton beams. The intensities of the γ-rays from the Coulomb excited levels of ^{82, 84}Kr were interrelated with those of the target nuclei ²⁷Al, ^{64, 66}Zn and ^{70, 72, 74, 76}Ge and yielded the values $\text{B(}\text{E}\text{2; 0}{}^{\mathrm{+}}{}_1\text{→ 2}{}^{\mathrm{+}}{}_1\text{= 0.255±0.009}\text{and}\text{0.122 ± 0.005}\text{e}\text{2 ·}\text{b}\text{2}\text{for}{}^{\mathrm{82,\; 84}}\text{Kr}$, respectively. In turn, these B(E2) values and the (E2; 0⁺₁ → 2⁺₁ values of the even Ge and Zn isotopes from the literature were used in a Doppler-shift attenuation analysis to obtain experimentally lacking electronic stopping power for Kr ions slowing down in Al, Zn and Ge. for Ge ions in Ge and for Zn ions in Zn.     

Spectroscopy of states in 33S by means of neutron-gamma angular correlation measurements

Levels of ³³S for E_x < 5 MeV have been studied with the ³⁰Si(α, nγ)³³S reaction at bombarding energies of E_α = 7.5 and 10.2 MeV. Neutron-gamma angular correlation experiments lead to three unambiguous spin and parity assignments: $\text{J}{}^{\mathrm{\pi }}\text{(3.83) =}\text{5}\text{2}{}^{\mathrm{+}}\text{, J}{}^{\mathrm{\pi }}\text{(4.048) =}\text{9}\text{2}{}^{\mathrm{+}}\text{and}\text{J}{}^{\mathrm{\pi }}\text{(4.09) =}\text{7}\text{2}{}^{\mathrm{+}}$. The measured branching and mixing ratios yield transition strengths for dipole and quadrupole transitions.     

Structure study of 12B from the elastic scattering of neutrons from 11B

Differential cross sections for neutrons scattered from ¹¹B have been measured for 2.2 MeV < E_n < 4.5 MeV. The differential cross section σ(θ) is fitted reasonably well by R-matrix parameters for broad states in ¹²B with assignments 1 ^? and (1) ⁺ at excitation energies E_x = 5.8 and 6.8 MeV respectively. The broad 1 ^? state has not been previously observed and is believed to be the 1 ^? member of the $\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{1}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ particle-hole multiplet predicted to exist by earlier shell model calculations. Its existence completes the identification of all of the levels of this multiplet (3 ^?, 2 ^?, 4 ^?, 1 ^?). The broad (1)⁺ level at E_x = 6.8 MeV has not been previously observed. States at excitation energies E_x = 5.61, 5.73 and 6.6 MeV have been assigned spins and parities of 3⁺, 3^? and (1)⁺ respectively. These states had previously been assigned spins of 2, 3 and $\text{≧ 1}$ respectively. Work on T = 1 states in ¹²C¹ has been compared with the present work.     

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.     

Investigation of the level schemes of 73,75,77As via the (3He,d) reaction

The reactions ^{72, 74, 76}Ge(³He, d) were investigated at E_lab = 23 MeV with a multigap and a Q3D magnetic spectrograph. Some 30 new levels up to $\text{E}{}^1\text{≈ 4}\text{MeV}$ have been found. The level schemes of the odd As isotopes ^{73, 75, 77}As up to $\text{E}{}^1\text{≈ 4}\text{MeV}$ seem to be rather independent of the neutron number. The good agreement of the low-lying level structure with the Coriolis-coupling model including a pairing force was verified and the vacancies of low-lying shell model states were extracted and compared with the simple pairing theory.     

High-spin states in 40K investigated with the 26MG + 16O reaction

Yrast levels in ⁴⁰K and ⁴⁰Ar have been investigated with the ²⁶Mg(¹⁶O, pnγ)⁴⁰K and ²⁶Mg(¹⁶O, 2pγ)⁴⁰Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The ⁴⁰K decay scheme involves new high-spin levels at E_tx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{= 5}{}^{\mathrm{?}}\text{, 6}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{, 9}{}^{\mathrm{+}}\text{and}\text{(8, 10)}{}^{\mathrm{?}}$ to the ⁴⁰K levels at E_x = 0.89, 2.88, 4.37, 4.88 and 6.23 and of $\text{J}{}^{\mathrm{\pi }}\text{= 4}{}^{\mathrm{+}}\text{and}\text{6}{}^{\mathrm{+}}\text{to the}{}^{40}\text{Ar}$ levels at E_x = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported.     

The reaction 36S(p,γ)37Cl: (I). Excitation energies and γ-ray branchings of bound states deduced from resonances in the range Ep = 500–2000 keV

Yield curves of the reaction ³⁶S(p, γ)³⁷Cl have been measured over the range E_p = 500–2000 keV with a highly enriched (81%) ³⁶S target. Proton energies, with a precision of typically 0.3 keV, and strengths are presented for the nearly 200 observed resonances. Several previously reported resonances, among which the well-known $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{?}}\text{, E}{}_{\mathrm{p}}\text{= 1887}\text{keV}$ analogue resonance, are proven to be multiplets.At 75 selected resonances in the ranges E_p = 500–1200 and 1800–2000 keV the decay schemes have been studied. These measurements also provide rather detailed information on the γ-ray branching ratios of more than 50 bound states of which the majority has not been observed previously. Precision excitation energies have been determined; for the levels with E_x < 5 MeV the median uncertainty amounts to 30 ppm. The reaction Q-value is Q = 8386.34 ± 0.23 keV.These precision data invalidate several previous spin and parity assignments to low-lying bound states of ³⁷Cl. They also provide a basis for the lifetime measurements and spin and parity assignments to be discussed in the following paper.     

Spin determination of states with stretched configurations in 16N and 32P via the (d, α) reaction at 52 MeV

The reactions ${}^{12}\text{C}\text{(}\text{d}\text{, α)}{}^{10}\text{B}\text{,}{}^{18}\text{O}\text{(}\text{d}\text{, α)}{}^{16}\text{N and}{}^{34}\text{S}\text{(}\text{d}\text{, α)}{}^{32}\text{P}$ have been investigated at E_d = 52 MeV. Vector analyzing powers as large as $\text{¦iT}{}_{11}\text{¦=0.85}$ are observed. They exhibit patterns characteristic for final spins I = |L?1|, L or L + 1 and provide spin determinations at least for states of unique L-transfer. Local, zero-range DWBA calculations assuming deuteron-cluster pick-up reproduce qualitatively the observed effects. The method has been tested for states of known spin, and then has been applied to determine spins of states with stretched coupling in ¹⁶N: J^π = 3⁺(3.96 MeV), 4^?(6.17 MeV) and in ³²P: J^π = 5⁺(4.75 MeV). There is strong evidence for further 5⁺ states in ³²P at 6.43, 7.96, 8.09 and 8.54 MeV.     

Distributions of i132 transfer strength in (τ, α)-induced population of odd-a platinum isotopes

The odd-A platinum isotopes ₇₈^{191, 193, 195, 197}pt have been populated by means of the (τ, α) reaction at E_τ = 50 MeV. Spectra covering a range of 4 MeV of excitation energy were obtained. Angular distributions for levels in this excitation range have been deduced. Only a few $\text{13}\text{2}{}^{\mathrm{+}}$ states are strongly populated in each isotope, the actual number being 1, 2, 3, and 2 for A = 191, 193, 195 and 197 respectively. The spacing between these peaks exhibits an interesting variation with neutron number. The data are compared with predictions of current quasiparticle-core coupling models.     

A folded diagram microscopic calculation of nuclear Coulomb displacement energies

We have performed a rather extensive microscopic calculation of the ¹⁷F-¹⁷O Coulomb energy differences ΔE_C. Our main purpose has been to study the effects of (i) folded diagrams, (ii) core polarization and (iii) the effects due to different nucleon-nucleon potentials, different single-particle spectra and different radial wave functions. Using a proton-neutron representation we have included higher-order Coulomb corrections like e.g. the coupling of valence particles to collective vibrations of the core.The inclusion of folded diagrams is very important; it is equivalent to a self-consistent treatment of the Q-box starting energies. It causes a significant suppression of the effect due to core polarization, its contribution to ΔE_C becoming small, about 0.03 MeV. As a consequence of this “self-correcting” behavior our results for ΔE_C are quite stable with respect to the choice of different single-particle spectra. Two rather different nucleon-nucleon potentials, the Reid soft-core potential and a meson exchange potential of the Bonn-Jülich group also lead to quite similar results for ΔE_C. In the case of $\text{J =}\text{5}\text{2}{}^{\mathrm{+}}$, for example, Δ_C calculated with the Reid potential ranges, depending on other assumptions, from 3.36 to 3.43 MeV and from 3.36 to 3.40 MeV with the Bonn-Jülich potential: Both are significantly smaller than the experimental value of 3.54 MeV. Optimizing the radial wave functions in the spirit of a Brueckner-Hartree-Fock theory improves the calculated values of ΔE_C for the $\text{J =}\text{1}\text{2}{}^{\mathrm{+}}$ state but not for $\text{J =}\text{5}\text{2}{}^{\mathrm{+}}\text{or}\text{3}\text{2}{}^{\mathrm{+}}$.We feel that other processes such as the explicit inclusion of core deformation or mesonic degrees of freedom or both are needed to explain the Coulomb displacement energies.     

Study of 11B at high excitations with the 9Be(3He,p)11B and 9Be(α, d)11B reactions

The nucleus ¹¹B has been studied over the excitation energy range from 8.5 MeV to 21.5 MeV with the ⁹Be(³He, p)¹¹B / reaction at / E_{³He = 38 MeV}. The analogs of the parent states in ¹¹Be have been located at 12.56, 12.92, 14.40, 16.44, 17.69, 18.0, 19.15 and 21.27 MeV. A complementary measurement with the ⁹Be(α, d)¹¹B reaction at E_α = 48 MeV demonstrates that the 16.44, 17.69, 18.0 and 19.15 MeV resonances have rather pure isospin $\text{T}{}_{\mathrm{f}}\text{=}\text{3}\text{2}$. The 14.40 MeV state is a strongly isospin-mixed analog of the $\text{5}\text{2}{}^{\mathrm{+}}\text{1.78}\text{MeV}$ state in ¹¹Be. It is argued that spin S = 1 transfer is involved in the excitation of the 16.44 MeV state and its 3.887 MeV parent in ¹¹Be in a two-step stripping process. The $\text{T}{}_{\mathrm{f}}\text{=}\text{1}\text{2}$ states and the lowest three $\text{T}{}_{\mathrm{f}}\text{=}\text{3}\text{2}$ states are compared with the predictions of DWBA utilizing shell-model form factors. It is concluded that the $\text{T}{}_{\mathrm{f}}\text{=}\text{1}\text{2}$ strength is more strongly fragmented than is implied by the calculations of Teeters and Kurath.