Investigation of high-spin states in 47Ca through double-step processes in the 48Ca(τ, α)47Ca reaction

In the ⁴⁸Ca (τ,α)⁴⁷Ca reaction at 25 MeV, some angular distributions are well reproduced by CCBA calculations, assumping double-step excitation of $\text{[}{}^{48}\text{Ca}{}^1\text{?}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{]}$ states. Unambigous J^π assignments are extracted from the analysis.     

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.     

Author index

High-spin states in ^167,168Hf and ^{170, 171}W have been excited by the reactions ${}^{159}\text{Tb}\text{(}{}^{14}\text{N}\text{, x}\text{n}\text{)}{}^{\mathrm{173\; ?\; x}}\text{Hf and}{}^{155}\text{Gd}\text{(}{}^{20}\text{Ne}\text{, x}\text{n}\text{)}{}^{\mathrm{175\; ?\; x}}\text{W}$. The yrast bands have been observed up to $\text{J}{}^{\mathrm{\pi }}\text{=}\text{49}\text{2}{}^{\mathrm{+}}$ in ¹⁶⁷Hf, J^π = 28⁺ in ¹⁶⁸Hf, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{45}\text{2}{}^{\mathrm{+}}$ in ¹⁷¹W and J^π = 22⁺ in ¹⁷⁰W. Both even-even nuclei display a strong backbend around J^π = 14⁺, whereas ¹⁶⁷Hf shows an upbend at ω ～- 0.33 MeV and ¹⁷¹W exhibits a progressive gain in aligned angular momentum above ω ～- 0.26 MeV. At even higher rotational frequencies, bridges have been found in the central valleys of the γ-γ correlation matrices at ω ～- 0.42 and 0.52 MeV for the Hf isotopes and ω ～- 0.45 and 0.47 MeV for the W isotopes. Deduced moments of inertia for the Hf isotopes using the correlation data show a smooth increase up to about the rigid-sphere value at ω ～- 0.5 MeV. The data are satisfactorily accounted for by cranked shell-model calculations. In particular, a qualitative interpretation is given for the experimentally observed systematic difference in the strength of the interaction potential for the N = 95 and N = 97 isotopes of Hf and W.     

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.     

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 (α, α), (α, α′) and (α, 3He) reactions on 12C at 139 MeV

The nucleus ¹²C was bombarded with 139 MeV α-particles to study the characteristics of the elastic, inelastic, and (α, ³He) reactions. An optical model analysis of the elastic data yielded a unique family of Woods-Saxon potential parameters with central real well depth V ≈ 108 MeV, and volume integral $\text{J}\text{4A}\text{≈ 353}\text{MeV}\text{·}\text{fm}{}^3$. By comparing the present results with those of other studies above 100 MeV, we find that the real part of the α-nucleus interaction decreases with increasing energy; the fractional decrease with energy is roughly one-half that observed for proton potentials. Using the optical potential parameters derived from the elastic scattering, first-order DWBA calculations with complex first-derivative form factors reproduced the inelastic scattering data to the 4.44 MeV (2⁺) and 9.64 MeV (3^?) states of ¹²C. For the 0⁺ state at 7.65 MeV it was necessary to employ a real, second-derivative form factor to fit the data. The deformation lengths β_lR_m and deformations β_l obtained in this and other experiments are summarized and compared. DWBA calculations using microscopic model form factors were also performed for the 2⁺ and 3^? states using the wave functions of Gillet and Vinh Mau. These reproduced the shapes and relative magnitudes of the differential cross sections. We also fit the shape of the 0⁺ differential cross section using a microscopic form factor which contains a node, which is similar to that occurring in the collective model second-derivative form factor. In the ($\text{α,}{}^3\text{He}$) reaction the differential cross sections to the ground state ($\text{1}\text{2}{}^{\mathrm{?}}$) and the 3.85 MeV ($\text{5}\text{2}{}^{\mathrm{+}}$) state in ¹³C could not be reproduced by zero-range local DWBA stripping calculations; it was necessary to employ finite-range and non-local corrections in the local-energy approximation. This DWBA analysis is notable in that unambiguous optical potentials were available for both entrance and exit channels. The ground state spectroscopic factor is in agreement with the prediction of Cohen and Kurath, while the relative spectroscopic factors agree fairly well with the rather few existing measurements of this kind.     

Spin assignments in 59Ni from the 58Ni(d, p)59Ni reaction

Angular distributions of the vector analyzing power and the absolute cross section were measured for the ⁵⁸Ni(d, p)⁵⁹Ni reaction at a deuteron energy of 10 MeV. The observed j-dependence of the vector analyzing power allowed unambiguous spin assignments for the following states in ⁵⁹Ni with excitation energies in $\text{MeV}\text{: 0.0,}\text{3}\text{2}{}^{\mathrm{?}}\text{; 0.341,}\text{5}\text{2}{}^{\mathrm{?}}$; $\text{0.465,}\text{1}\text{2}{}^{\mathrm{?}}\text{; 0.879,}\text{3}\text{2}{}^{\mathrm{?}}$; $\text{1.303,}\text{1}\text{2}{}^{\mathrm{?}}\text{; 1.686,}\text{5}\text{2}{}^{\mathrm{?}}\text{; 3.454,}\text{3}\text{2}{}^{\mathrm{?}}\text{; 3.858,}\text{3}\text{2}{}^{\mathrm{?}}\text{; 4.495,}\text{5}\text{2}{}^{\mathrm{+}}$. The data are well reproduced by DWBA calculations employing deuteron and proton optical model parameters obtained from analyses of elastic scattering cross sections and polarizations. A tentative spin assignment of $\text{9}\text{2}{}^{\mathrm{+}}$ is made for the level at 3.061 MeV. A $\text{5}\text{2}{}^{\mathrm{+}}$ assignment to the level at 3.538 MeV is suggested on the basis of the empirical behavior of the j-dependence of the vector analyzing power for l = 2 transitions. Measurements of the vector analyzing power for the four low-lying ⁵⁹Ni states formed by l = 1 transfer were made for angles from 2.5° to 15° using a magnetic spectrograph. A very strong j-dependence was observed for these far-forward-angle measurements in agreement with DWBA predictions.     

Elastic and inelastic pion scattering on C and C at 100 MeV

Angular distributions of π⁺ and π^? at 100 MeV incident energy were measured for elastic and inelastic scattering from ¹²C and ¹³C. Elastic data were obtained between 6° and 180°. Inelastic scattering on the 2⁺ (4.4 MeV), 0⁺ (7.6 MeV), 3^? (9.6 MeV) and 1⁺ (12.7 MeV) states of ¹²C and on the $\text{3}\text{2}{}^{\mathrm{?}}\text{(3.7}\text{MeV}\text{),}\text{5}\text{2}{}^{\mathrm{?}}\text{(7.5}\text{MeV}\text{),}\text{9}\text{2}{}^{\mathrm{+}}\text{(9.5}\text{MeV}\text{)}$ and 11.7 MeV states of ¹³C was mea ¹²C results are compared to a Δ-hole model.     

The 65Cu(p,t)63Cu reaction and the structure of 63Cu

The ⁶⁵Cu(p, t)⁶³Cu reaction has been studied with 18.0 and 19.5 MeV protons. The states in ⁶³Cu at 1.547 and 2.498 MeV are each assigned $\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{?}}$ on the basis of angular distributions indicating mixed L = 0 and L = 2 transfer. Relative cross sections for L = 2 transfer to the low-lying states are compared with predictions of the shell model and particle-core model.     

Incomplete fusion in 12C+160Gd collisions

The mechanism of the production of fast α-particles in ¹²C induced reactions was studied over a wide range of bombarding energies (7.5–16.7 MeV/A) by measuring α-γ coincidences. Absolute cross sections for ${}^{160}\text{Gd}\text{(}{}^{12}\text{C}\text{, αx}\text{n}\text{)}{}^{\mathrm{168?x}}\text{Er and}{}^{160}\text{Gd}\text{(}{}^{12}\text{C}\text{, 2αx}\text{n}\text{)}{}^{\mathrm{164?x}}\text{Dy}$ reactions, as well as inclusive α-particle production cross sections, have been determined. Depending on the bombarding energy, a fraction of 0.2–0.4 of the singles α-particles can be explained as resulting from incomplete fusion reactions (¹²C, α) and (¹²C, 2α) which correspond to a capture of “⁸Be” and “⁴He”, respectively. The remaining fragments of the projectile have, on the average, the beam-velocity energies and their angular distributions are forward peaked. Distributions of side-feeding to the yrast bands in the target-residue nuclei indicate that low partial waves are strongly hindered in the incomplete fusion reactions. The energy dependence of the cross sections for (¹²C, α) and (¹²C, 2α) incomplete fusion as well as for (¹²C, 3α) projectile breakup is given. A generalized concept of critical angular momentum which explains a competition between complete fusion, incomplete fusion and breakup reactions is proposed.     

The (g92)2 residual interaction from 87Sr(d,t)86Sr

Differential cross sections for ⁸⁷Sr(d, t)⁸⁶Sr transitions to the $\text{(1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}$ states of ⁸⁶Sr were obtained with the Pittsburgh 18 MeV deuteron beam and the Enge split-pole spectrograph. States of ⁸⁶Sr up to 3.82 MeV in excitation were studied with a total resolution of 12 keV. Successful distorted-wave Born approximation (DWBA) predictions for ⁸⁷Sr(d, t) ⁸⁶Sr angular distributions permitted the extraction of l-values and spectroscopic strengths. The sum-rule value agrees with the observed value for the $\text{(1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}$ configuration. The observed $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ strength is spread over 13 states. Contrary to an earlier interpretation, the 0⁺ ground state is found to contain only 65% of the strength. Similarly, the full 4⁺ strength is not located in a single state. The new data change the interpretation of the $\text{(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}$ spectrum of ⁸⁶Sr. They significantly alter the deduced low-spin matrix elements and bring them into much closer agreement with those derived from ⁸⁸Y. Several new negative-parity states dominated by l = 1 orbital angular momentum transfer have also been identified.     

Spectroscopic study of 15N states with the reaction 14C(d,n)

Energy and angular distributions of neutrons from the reaction ¹⁴C(d, n)¹⁵N have been measured at 6.5 MeV deuteron energy. The DWBA analysis yielded l-values and absolute spectroscopic factors for fifteen states in ¹⁵N below 10 MeV excitation energy. For the 9.23 MeV level J^π is determined to be $\text{3}\text{2}$⁺ or $\text{5}\text{2}$⁺, for the 9.93 MeV level the data suggest $\text{J}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{+}}$. The spectroscopic factors are in qualitative agreement with pure jj coupling and in semi-quantitative agreement with shell-model calculations.     

Search for 8+ strength in 16O via the 12C(α, α2)12C1(7.66 MeV) reaction

Closely spaced angular distributions have been measured for the ${}^{12}\text{C}\text{(α, α}{}_2\text{)}{}^{12}\text{C}\text{1(7.66}\text{MeV}\text{)}$ reaction between E_α = 17.39 and 20.5 MeV in a search for 8⁺ strength in ¹⁶O. No evidence of 8⁺ strength is found, but evidence is found for a narrow 7^? resonance at 21.52 MeV excitation.     

Finding out about B mesons and B-B0 mixing on the ϒ‴ resonance

We point out that existing data on the resonance shape of ?? provide useful bounds on the B meson mass: M(??)? 2 M(B) = 9_?6⁺¹² MeV if one uses the quark pair creation model. From the upper limits on $\text{B}{}^1\text{B}\text{+}\text{B}\text{B}{}^1$ production one gets M(??) ? 2M(B) < 37 MeV. We show how measurements of inclusive semileptonic B decays allow us to determine the electromagnetic mass splitting M(B⁰) ? M(B^?) without having to identify exclusive B decays. As byproducts one obtains information on the B⁰-B^? lifetime ratio and on $\text{B}{}^0\text{-}\text{B}{}^0$ mixing.     

(f72)7,0−2 configuration high-spin states in 60Co strongly excited in the 62Ni(d, α) reaction

The ${}^{62}\text{Ni}\text{(}\text{d}\text{, α)}{}^{60}\text{Co}$ reaction has been studied with 78 MeV vector polarized deuterons. Angular distributions of the differential cross section and vector analyzing power have been measured for strongly populated states in ⁶⁰Co up to an excitation energy of 5 MeV. The transferred orbital and total angular momenta L and J were determined from the characteristic shapes of the differential cross sections and vector analyzing powers yielding a number of new spin assignments. The J^π = 7⁺ stretched configuration was found to be distr least over nine states located at 1.51, 3.09, 3.46, 3.67, 3.78, 4.04, 4.55, 4.70 and 4.80 MeV.     

Generalized neutron particle-hole states in an extended unified model

Negative-parity levels in the doubly even N = 82, Z nuclei, with 3.0 MeV ? E_x? 6.0 MeV are described in an extended unified-model approach, where neutron hole states in the Z = 50, N = 82 closed shell core, (i.e. ) are coupled to the low-lying levels (E_x ? 2.0 MeV) of the odd-neutron N = 83, Z nuclei. This particular configuration space of generalized neutron particle-hole states (GNPH) is particularly suited for describing negative-parity levels obtained in proton inelastic scattering through isobaric analogue resonances (IAR), corresponding to the N = 83, Z low-lying nuclear levels. Level schemes as well as partial decay widths and angular distributions are calculated and compared extensively with the available experimental data. Also spectroscopic factors, as well as wave functions, deduced from the experimental results are studied in detail. Thus in the cases of ¹³⁶Xe, ¹³⁸Ba, ¹⁴⁰Ce, ¹⁴²Nd and ¹⁴⁴Sm, some of the important neutron particle-hole configurations can uniquely be determined in the energy region 3.0 MeV ?E_x ? 6.0 MeV.     

Search for highly excited states in 8Be

Excitation functions and angular distributions of the reactions ${}^7\text{Li}\text{(}\text{p}\text{, α)α}{}^1$ and ${}^6\text{(}\text{Li}\text{(}\text{d}\text{, α)α}{}^1$ have b investigated for the excitation-energy region E_X = 21?28 MeV in ⁸Be ($\text{α}{}^1$ denotes the first excited state of the α-particle). pronounced resonant structure has been observed in both channels around E_X = 24 MeV. It is excited simultaneously by odd and even angular momenta. The experimental results are discussed in the light of two models, the αα¹ cluster model and the symplectic model which take into account the configuration interaction (core excitation) in different manners.