Excitation of the deeply bound g92 neutron hole state in 117Sn by a neutron pickup reaction with 81.7 MeV 3He particles

Neutron hole states have been investigated by neutron pickup reactions on ⁹²Mo, ¹¹⁸Sn, ¹⁴⁰Ce and ²⁰⁸Pb with 81.7 MeV ³He particles. A strong effect of angular momentum mismatch has been observed to reduce the cross section for low-spin orbits. It causes the deeply bound $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ orbit to appear in the spectrum of the α-particles from the ${}^{118}\text{Sn(τ, α)}{}^{117}$Sn reaction as a strong broad peak. It may provide a nice tool for investigating the coupling mechanism between the deeply bound holes and the core.     

The h112 and g72 band structures in 131Ce and 129Ce

High-spin levels in ^{129, 131}Ce have been produced by the reactions ^{116, 118}Sn(¹⁶O, 3n) ^{129, 131}Ce and studied by in-beam γ-ray spectroscopic techniques. Two strongly populated band structures are observed. The odd-parity levels based on a $\text{9}\text{2}{}^{\mathrm{?}}$ state constitute a system explained in the triaxial-rotor-plus-particle model as the result of the coupling of an $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ neutron-hole to a prolate-type triaxial core. The even-parity band built on a $\text{7}\text{2}{}^{\mathrm{+}}$ state corresponds to collective excitations associated with a neutron-hole in the $\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ shell. Backbending effect observed in the yrast cascade is discussed.     

A comparative study of proton states in 121,123,125,127,129,131I excited by (α, t) and (3He,d) reactions

Proton states in ^{121,123,125,127,129,131}I were investigated by means of Te(α, t)I and Te(³He, d)I reactions at 36 MeV bombarding energy using a Q3D magnetic spectrograph. Angular distributions were measured for transitions to ¹²¹I. From ratios of cross sections of transitions in the reactions (³He, d) and (α, t) to final states in ^125–131I, the transfered orbital angular momenta and relative spectroscopy factors are extracted. New levels are observed including $\text{7}\text{2}{}^{\mathrm{+}}\text{and}\text{11}\text{2}{}^{\mathrm{?}}$ single-particle strength fragments. The results are interpreted using the three-particle-cluster — phonon coupling model.     

Angular correlation experiments in the reactions 2H(α, nα)p and 2H(α, pα)n and comparison with the Faddeev theory and the resonating group method

At the Hamburg Isochronous Cyclotron angular correlation experiments were carried out in the reactions ²H(α, nα)p and ²H(α, pα)n, in order to determine the tensor polarization of the ground-state resonances ${}^5\text{Li}\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$ and ${}^5\text{He}\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$, respectively. We find that the observables for the two mirror reactions ${}^2\text{H}\text{(α,}\text{n}\text{)}{}^5\text{Li}\text{and}{}^2\text{H}\text{(α,}\text{p}\text{)}{}^5\text{He}$ are charge-dependent. This result is interpreted as evidence for a violation of charge symmetry.In the whole phase-space region absolute break-up cross sections are generally well reproduced by the Faddeev theory. On the other hand, we find that the resonating group method which has up to now been mainly applied to two-body reactions can also provide valuable information for break-up reactions. The predictions of Hackenbroich, Schütte and coworkers are in quite good agreement with the measured tensor polarization of ⁵He and ⁵Li and the corresponding angular correlation functions.     

Deformed states of neutron-deficient cerium and neodymium nuclei

High-spin levels in Ce and Nd isotopes excited by the reactions ^120,122Sn(¹⁶O, 3n) ^{133, 135}Ce and ^{122, 124}Te(¹⁶O, 3n)^{135, 137}Nd have been studied by in-beam γ-ray spectroscopic methods (prompt and delayed spectra, excitation functions, angular distributions and γ-γ coincidences). Bands built on the $\text{11}\text{2}{}^{\mathrm{?}}$ isomeric levels in ¹³⁵Ce and ¹³⁷Nd and on the $\text{9}\text{2}{}^{\mathrm{?}}$ground states in ¹³³Ce and ¹³⁵Nd have been found. A prolate deformation is required for these nuclei in order to explain the E2/M1 mixing ratios and the level ordering of these bands.     

The interaction of 33 MeV polarised helions with 30Si

Distributions of cross sections and analysing powers have been measured over the range ～ 14°–100° c.m. for the $\text{(}{}^3\text{H}\text{,}{}^3\text{He), (}{}^3\text{H}\text{,}{}^4\text{He), (}{}^{\mathrm{<mtext>3</mtext><mtext>H</mtext>}}\text{,}{}^2\text{H)}$ reactions at 33.4 MeV incident e using a ～ 95 % enriched ³⁰Si target. Phenomenological optical-model analyses of the elastic-scattering data have been carried out. A DWBA analysis of the inelastic-scattering data for the 2.24 MeV (2⁺) and 5.49 MeV (3^?) states of ³⁰Si has yielded values of the deformation β₂ and β₃. The j-dependence of the analysing powers for the (³He, ⁴He) and (³He, ²H) reactions has identified the 6.71 MeV level of ²⁹Si as a $\text{5}\text{2}{}^{\mathrm{+}}$ state, and a level near 9.5 MeV in ³¹P as a possible $\text{7}\text{2}{}^{\mathrm{?}}$ state. Spectroscopic factors for ten states in ²⁹Si and seven states in ³¹P have been deduced and are compared with other work. The extent to which the data defines the ³He spin-orbit potential is discussed.     

The doubly odd nucleus 144Pm: (II). Interpretation

Results from the proton transfer reactions, ¹⁴³Nd(³He, d) and ¹⁴³Nd(α, t), and γ-ray studies have been used to characterize the levels in ¹⁴⁴Pm. The spins, $\text{(}{}^3\text{He, d)}\text{(α, t)}$ cross section ratios and γ-ray branching ratios for the states below 600 keV can be interpreted consistently in terms of the mixed $\text{π2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{ν2}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and $\text{π1}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{ν2}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ shell-model configurations. The γ-ray intensity ratios measured in the ¹⁴¹Pr(α, nγ) and ¹⁴⁴Nd(p, nγ) reactions exhibit a strong and smooth dependence on level spin. Theoretical calculations employing a residual surface delta interaction are in reasonable agreement with the twelve observed low-lying negative parity states. The eight positive parity states between 841 and 1451 keV are presumed to arise from the $\text{π1}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{ν2}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ configuration.     

The five-nucleon system above the three-particle threshold

Compound nucleus states in ${}^5\text{Li}$ and ${}^5\text{He}$ have been investigated with the ${}^3\text{He(d,p)pt}$ and ${}^3\text{H(d,n)pt}$ three-particle reactions. The observed $\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{?}}$ states (E_X≈20 MeV) can be understood, in analogy to the ground states of the A=5 system, by coupling a $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ nucleon to the first 0⁺ excited state of ${}^4\text{He}$.     

Two-step processes in the 40Ca(α, 3He)41Ca reaction

The ⁴⁰Ca(α, ³He) reaction has been studied at 36 MeV incident energy. About fifty levels have been observed up to 7.1 MeV excitation energy and angular distributions were measured from 6–60° using a split-pole spectrometer. A local zero-range DWBA analysis has been carried out, and the deduced l-assignments and spectroscopic factors are compared with those obtained from previous neutron stripping experiments. Core-excited states in ⁴¹Ca with a [3^? ? f_7,2], [2⁺ ? f_7,2] and [5^? ? f_7,2] component previously observed in inelastic scattering experiments, are selectively excited by the (α, ³He) reaction. Their angular distributions are compared with coupled-reaction-channel calculations, assuming a pure two-step reaction mechanism. The agreement between theory and experiment may be considered as rather satisfactory for a number of levels. In particular the $\text{1}\text{2}{}^{\mathrm{+}}\text{and}\text{3}\text{2}{}^{\mathrm{+}}$ levels and the high-spin states with $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{?}}\text{,}\text{11}\text{2}{}^{\mathrm{+}}\text{,}\text{15}\text{2}{}^{\mathrm{+}}\text{and}\text{17}\text{2}{}^{\mathrm{+}}$ are successfully described within the framework of the weak-coupling model.     

High spin collective excitations in 101Ru

The energy level structure of ¹⁰¹Ru was studied using the reactions ¹⁰⁰Mo(α, 3n)¹⁰¹Ru and ¹⁰⁰Mo(³He, 2n)¹⁰¹Ru. Excitation functions, γγ coincidences and γ-ray angular distributions were measured. Three ΔI = 2 cascades proceeding to a $\text{5}\text{2}{}^{\mathrm{+}}$, $\text{7}\text{2}{}^{\mathrm{+}}$ and $\text{11}\text{2}{}^{\mathrm{?}}$ state were observed. A decay scheme is presented showing energies up to 5849 keV and spins up to $\text{35}\text{2}$. The bands are discussed within the framework of the Nilsson model with Coriolis coupling in which the recoil effect has been properly introduced.     

Level structure in 117Sb investigated in the decay of the isomeric three-quasiparticle state

The level structure of ¹¹⁷Sb was investigated in the reactions ¹¹⁵In(α, 2nγ)^117mSb, ¹¹⁷Sn(d, 2nγ)^117mSb and ¹¹⁷Sn(p, nγ)^117mSb. In order to confirm level sequences and to assign spins and parities to levels populated in the decay of the isomeric three-particle state $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ = 340 μs), prompt and delayed γ-ray spectra, lifetimes, γ-γ coincidences, γ-ray angular distributions, conversion electrons and excitation functions were measured. The spin $\text{25}\text{2}$⁺ of the isomeric state can be explained by the three-particle configuration [$\text{π(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{); v(}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}^2\text{10}{}^{\mathrm{+}}\text{]}\text{25}\text{2}{}^{\mathrm{+}}$. This is supported by the experimentally determined g-factor of g = O.115 ± 0.006. Other levels in ¹¹⁷Sb can be interpreted as particle states coupled to anharmonic vibrations of the core. The existence of an excited $\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$ quasirotational band is experimentally proved and is supported by calculations of the equilibrium deformation.     

Single-particle and core-excited states in 49Sc: (II). The 48Ca(α, t)49Sc reaction

The ⁴⁸Ca(α, t)⁴⁹Sc reaction has been studied at 36 MeV incident energy. About eighty levels have been observed up to 7.5 MeV excitation energy and angular distributions were measured from 6° to 58°, using a split-pole spectrometer. A local zero-range DWBA analysis has been carried out, and the deduced l-assignments and spectroscopic factors are compared with those obtained from the (³He, d) reaction. In the other hand, a large number of angular distributions cannot be reproduced by the DWBA calculations; they have been compared with the results of coupled-reaction-channel calculations, assuming two-step excitation of weak coupling states with a [${}^{48}\text{Ca}{}^1\text{?}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$] structure. Good agreement between experimental angular distributions and two-step predictions is obtained for several ⁴⁹Sc levels, suggesting spin and parity assignments. Moreover, as rather large cross sections are predicted for two-step excitations, it is concluded that, generally, these processes cannot be neglected in the analysis of (α, t) reactions.     

Strong coupled-channels effects in the 9Be(α, t)10B reaction

Differential cross sections were measured for the reactions ${}^9\text{Be}\text{(α, α')}{}^9\text{Be}\text{,}{}^9\text{Be}\text{(α,}\text{t}\text{)}{}^{10}\text{B and}{}^9\text{Be}\text{(α,}{}^3\text{He}\text{)}{}^{10}\text{B at}\text{E}{}_{\mathrm{\alpha }}\text{= 65}\text{MeV}$ for angles ranging from θ_lab = 6° to 48°. Optical-model analysis was performed for elastic α-scattering from ⁹Be at E_α = 48, 65 and 104 MeV, and DWBA and CC calculations were done for the inelastic α-scattering at E_α = 65 MeV. DWBA calculations for the ⁹Be(α, ³He) reactions do not fit the transfer data so well and extracted spectroscopic factors are in disagreement with those of Cohen and Kurath and with values obtained from other reactions. Full CRC calculations assuming a band structure for the low-lying states of ¹⁰B and employing a modified set of Cohen and Kurath spectroscopic factors yield globally better fits both in shape and in absolute cross section for differential cross sections to low-lying states in ¹⁰B obtained in ⁹Be(α, t)¹⁰B at $\text{E}{}_{\mathrm{\alpha }}\text{= 65}\text{MeV and}{}^9\text{Be}\text{(}{}^3\text{He, d}\text{)}{}^{10}\text{B at}\text{E}{}_{\mathrm{<mtext>d</mtext>}}\text{= 17}\text{MeV}$. In general, strong coupled-channel effects mainly affecting the distorted waves are observed both in entrance and exit channels.     

E0 transitions in 114,116,118Sn

Low-lying 0⁺ states have been excited in the (p, p′) reaction via the$\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ isobaric analog resonance in ^114,116Sn and in radioactive decay in ¹¹⁸Sn. From conversion electron measurements, values of $\text{X =}\text{B(}\text{EO}\text{;0}{}^{\mathrm{+}}\text{→ 0}{}_1{}^{\mathrm{+}}\text{)}\text{B(}\text{E}\text{2; 0}{}^{\mathrm{+}}\text{→2}{}_1{}^{\mathrm{+}}\text{)}$ are obtained from the 1953 keV state in ¹¹⁴Sn, 1757 and 2027 keV states in ¹¹⁶Sn and 1758 and 2056 keV states in ¹¹⁸Sn.     

High spin states in 57Co

High spin states of ⁵⁷Co have been studied via prompt γ-ray spectroscopy in the reactions ⁴⁸Ti(¹²C, p2n) and ⁵⁴Fe(α, p) at 26–48 MeV and 12–24 MeV, respectively. The energies and decay modes of these levels were determined from the analysis of γ-ray singles and γ-γ coincidence spectra, excitation functions, angular distributions and correlations. The relevant lifetimes were measured by the Doppler-shift attenuation method. The new levels established in this work are at 4037, 4814 and 5918 keV with the most probable J^π assignment of $\text{15}\text{2}{}^{\mathrm{?}}$, if $\text{17}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$, respectively. The previously known level at 2524 keV was assigned to have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{?}}$. These together with the known $\text{9}\text{2}{}^{\mathrm{?}}$(1224 keV) and $\text{11}\text{2}{}^{\mathrm{?}}$(1690 keV) levels constitute the yrast states of ⁵⁷Co. The measured lifetimes of the above six levels are (in order of increasing energies) 0.085±0.030, 0.32±0.10, 0.16±0.06, 0.10_?0.07^+0.06, 1.5_?0.5⁴ and 0.17_?0.07^+0.08 ps, respectively. Comparisons with some theoretical calculations are presented.     

Medium-spin levels and the character of the 20.4 ns 132+ isomer in 145Gd

Levels of the N = 81 nucleus ¹⁴⁵Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the ¹⁴⁴Sm(³He, 2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin $\text{21}\text{2}{}^{\mathrm{+}}$, five other high-spin non-yrast states and a new 20.4 ns $\text{13}\text{2}$ isomer at 2200.2 keV in ¹⁴⁵Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 ± 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1 + M2 + E3 transition to the $\text{v}\text{h}{}^{\mathrm{?1}}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ state. We propose an octupole $\text{v}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{j}{}^{\mathrm{?2}}\text{× 3}{}^{\mathrm{?}}$ main configuration for the isomer, analogous to the 997 keV $\text{13}\text{2}{}^{\mathrm{+}}$ isomer in ¹⁴⁷Gd. The levels of ¹⁴⁵Gd are discussed on the basis of the spherical shell model.     

High-spin particle states in 151Sm studied with the (α, 3He) reaction

High-spin states have been located in ¹⁵¹Sm by means of the (α, ³He) reaction with 40 MeV α-particles. The scattered particles were momentum analyzed in a QMG/2 magnetic spectrometer and recorded in a position sensitive detector. Several high-spin states were observed in the energy range below 1.7 MeV excitation. The previously unknown strongly populated levels at 867 and 1480 keV can most likely be interpreted as $\text{13}\text{2}{}^{\mathrm{+}}$ states. Both the deduced nuclear structure factors and the energy location of these levels are in excellent agreement with a simple Coriolis coupling calculation.     

(3He, 2n) excitation functions for some light nuclei

Excitation functions have been measured for the reaction ⁹Be(³He, 2n)¹⁰C over the range $\text{E(}{}^3\text{He}\text{) = 10–41}\text{MeV}$ and for the reaction ²⁷Al(³He, 2n)²⁸P over the range $\text{E(}{}^3\text{He}\text{) = 14–41}$ MeV by detecting β-delayed γ-rays. An excitation function has also been measured for the reaction ²⁴Mg(³He, 2n)²⁵Si over the range $\text{E(}{}^3\text{He}\text{) = 21–43}\text{MeV}$ by detecting β-delayed protons.     

High-spin states in 103Ag and particle-core coupling at intermediate deformation

The ¹⁰³Ag nucleus has been studied using the ¹⁰³Rh(α, 4nγ)¹⁰³Ag and ¹⁰³Rh(³He, 3nγ)¹⁰³Ag reactions. A set of standard in-beam measurements involving relative excitation function measurements of γ-rays, γ-γ-Δt coincidences, conversion electron measurements and angular distribution and linear polarization measurements of emitted γ-rays have been performed. Excited states with spin values up to $\text{27}\text{2}$ are populated in this nucleus. Among these excitations a positive-parity band built on the $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}\text{or}\text{9}\text{2}{}^{\mathrm{+}}$ state can be distinguished. This band has similar properties as the band observed in ¹⁰⁵Ag. The experimental data on the band in ^{103, 105}Ag are compared to the prediction of the Nilsson model with Coriolis coupling at intermediate deformation ε = 0.10?0.15. Energy levels of the positive-parity bands are reproduced satisfactorily by the calculations assuming either a $\text{K =}\text{7}\text{2}{}^{\mathrm{+}}\text{[413]}\text{or}\text{K =}\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$ band head. However, electromagnetic properties of the levels, branching and mixing ratios, are better reproduced when assuming the $\text{K =}\text{7}\text{2}{}^{\mathrm{+}}$ band head. Attenuation of the Coriolis interaction was introduced in order to improve the fit of the calculated energies of the levels to the experimental values.