The Isobaric-Analogue Resonance States in the Fe56 Nucleus

Gamma ray spectra from the reaction Mn⁵⁵(p, γ) Fe^56ß have been measured at the isobaric-analogue resonances at E_p = 1769 ± 4 keV and 1806 ± 4 keV respectively with a 15 cm³ Ge(Li) dedector. Double correlation for the transition from the resonance level to the second excited state of Fe⁵⁶ has been measured for the two cases. Proton elastic scattering was also studied at each resonance at the angle 150°. Analysis of the (p, y) and (p, p) works yields a J^π assignment 4⁺ or 5⁺ and 3⁺ for the two mentioned resonance states, respectively, which are the isobaric-analogues of the 0.454 MeV and 0.486 MeV states of Mn⁵⁶. The proton partial width and the total width for each resonance state were also determined.     

Isobaric Analogue State of the 341 KeV Level of Mn56 and Fe56

When Mn⁵⁵ is bombarded by protons, a proton capture resonance is detected at E_p = (1678 ± 4) KeV. The spectral and angular distribution studies of the (p, γ) and (p, p) reactions at this resonance have established J^π = 3⁺, l_p, = 1, Γ_p = (1 = 0.2) KeV and Γ = 17 KeV for the energy level at (11836 ± 4) KeV in the Fe⁵⁶ nucleus. Comparison of the present results with those obtained by (n, γ) and (d, p) reactions on the Mn⁵⁵ nucleus suggests that this resonance state is most probably the isobaric analogue of one member of the doublet at 341 KeV in the Mn⁵⁶ nucleus.     

Isobaric Analogue State of the 0.211 MeV Level of Mn56 in Fe56

Gamma-ray spectrum from the reaction Mn⁵⁵(p, γ) Fe⁵⁶ at the isobaric analogue resonance at E_p = 1537 ± 4keV has been measured with a 15 cm³ Ge(Li) detector. Double and triple angular correlations at this resonance state have been measured. Proton elastic scattering was studied also at this resonance at the angles 135° and 150°. Analysis of these data yields a spin and parity assignment 2+, proton radiative width 2 ± 0.2 keV and total width 9 keV to this resonance state which is the isobaric analogue of the third excited state of Mn⁵⁶ at excitation energy 0.211 MeV.     

Elastic Scattering of α-Particles on Be9

The differential cross-section for the elastic scattering of He⁴ particles on Be⁹ has been studied in the bombarding energy range 1.4-2.5 MeV. The excitation functions for the elastically scattered α-particles from Be⁹ were measured at six angles 90°, 125°, 132°, 140°, 150° and 160° in the centre of mass system. A clear and pronounced resonance is observed in the measured cross-section at incident α-particle energy 1.93 MeV. Analysis of the data in terms of the single level approximation theory leads to the assignment Jπ = 5+/2 for the observed resonance. Reduced and partial widths for elastic scattering were determined.     

Elastic and inelastic scattering of polarized protons from even n=82 nuclei near isobaric analog resonances

Excitation curves for the elastic and the inelastic scattering of polarized protons on the target nuclei ¹³⁸Ba, ¹⁴⁰Ce, ¹⁴²Nd and ¹⁴⁴Sm have been measured in the energy region of prominent isobaric analog resonances. A detailed analysis of the data is presented. Definite J^π assignments are given for a number of parent analog states. Spectroscopic factors and amplitudes for configurations with the core in the ground state or in the 2₁⁺ excited state are derived from the elastic and inelastic proton decay amplitudes. They show consistency with sum rules including orthogonality conditions. Different methods for the-calculation of single particle decay widths have been applied. The qualitative agreement with present unified model calculations is remarkable; an overestimattion of the weak coupling structure, however, becomes apparent.     

Nuclear level widths in 113Sb from particle-X-ray coincidences

The particle-X-ray coincidence method is applied in (p, p₀) and (p, p′) reactions on ¹¹² Sn at 7.138, 10 and 12 MeV proton energy to measure the width of compound nuclear states in ¹¹³Sb. The united-atom K X-ray intensities observed in coincidence with inelastic proton scattering (35⁺⁷⁸_?35, 80 ± 50 and 250 ± 80 counts at the respective energies) yield mean level widths for ¹¹³Sb of ?3.9 eV, 16.6 ± 15.1 eV, and 19.1 ± 11.1 eV at the excitation energies 10.1, 13 and 15 MeV, respectively. From X-ray coincidences with elastic proton scattering, upper limits for the compound elastic component are derived. No united-atom X-rays were detected in short runs at 7 MeV on ⁹²Mo and ¹⁰⁶Cd. A comparison of nuclear state widths from X-ray method, crystal blocking technique and fluctuation averaging is given.     

TheP +19Nes- wave resonant state in20Na at stellar energies

The first excited state above the p +¹⁹Ne threshold in²⁰Na has been identified at 2.637 MeV (± 15 keV) with J^π=0⁺ or 1⁺ from the²⁰Ne(³He, t)²⁰Na reaction, suggesting this state to be the s-wave resonance in the p +¹⁹Ne scattering at stellar energies.     

Line shape and excitation strength of the first excited state in9Be

The line shape and the excitation strength of the very weak first excited J ^π =1/2⁺ state at E_x=1.684 MeV in Zeitschrift für Physik Zeitschrift für Physik⁹Be has been investigated with high-resolution inelastic electron scattering at E₀=45 and 49 MeV and scattering angles θ=105°, 117°, 129° and 165°, and with high-resolution inelastic proton scattering at E₀=13MeV and θ=15° and 18°. Due to lying just above the neutron threshold the level has a strongly asymmetric line shape which in both experiments can be described consistently with a Breit-Wigner expression modified on the low energy side by the threshold behaviour of the cross section. The resonance energy is E_R=1.684 ± 0.007 MeV and the width T=217± 10 keV in thec.m. system. A single particle potential model calculation reproduces the line shape and the resonance parameters fairly well. In addition, the inelastic electron scattering form factor has been measured. In the range of momentum transfersq =0.24-0.46 fm^?1 it is dominated by a 0p_3/2→ 1s_1/2 particle-hole transition. The transition is mainly longitudinal and of isoscalar nature with a strength of B (E1)↑ =0.027 + 0.002 e² fm², but a small M2 contribution ofB(M2)↑=8.8 ±1.5 μ _N ² fm² has also been detected.     

Alpha-decay widths in 20Ne

The α-decay of several unbound levels in ²⁰Ne has been studied by ¹⁶O(α, α) elastic and inelastic scattering. A narrow resonance, Γ_c.m. = 13±4 eV, with J^π = 5^? was found at $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{(}{}^{20}\text{Ne}\text{) = 8.451±0.005}\text{MeV}$ and is associated with the lowest K = 2^? quasirotational band. Several new, narrow resonances were found between E_x = 16.0?18.4 MeV. Reduced α-decay widths have been obtained for the lowest K = 0⁺, 2^? and 0^?bands. For states described predominantly by the (8, 2) representation of SU(3) we note a reduction of the reduced widths with increasing spin. Reduced widths of positive parity bands are reviewed.     

Study of elastic and inelastic scattering of protons from 74Ge at isobaric analogue resonances

Excitation functions of the elastic and the inelastic proton scattering leading to the ground state and to the 2⁺ (0.596 MeV) state in ⁷⁴Ge were measured at 90°, 125°, 140° and 165° at bombarding energies from 3.34 to 5.4 MeV. Ten isobaric analogue resonances in ⁷⁵As were identified. Five of these resonances decay to the 2⁺ excited state in ⁷⁴Ge. Angular distributions of the inelastically scattered protons were measured at bombarding energies corresponding to these resonances. The partial widths of the isobaric analogue states for decay to the ground state and to the 2⁺ excited state in ⁷⁴Ge were determined as well as the l-values of the captured protons and the spins of the resonances. The Coulomb displacement energy for the pair ⁷⁵As-⁷⁵Ge was found to be 10.01 MeV. A comparison is made with the parent analogue states in ⁷⁵Ge. The results indicate that several levels of ⁷⁵Ge may be described as having a large component of a single particle state coupled to the first 2⁺ excited state in ⁷⁴Ge, and that the 2⁺ state has a configuration with a large 2p-2h component.     

Energy levels of 56Co studied by the 58Ni(d, α)56Co reaction near 0°

Tensor analyzing powers, T₂₀, of outgoing α-particles in the ⁵⁸Ni($\text{d}$, α)⁵⁶Co reaction at detection angles near 0° have been measured for excited states in ⁵⁶Co for beam energies of 6.75, 7.0, 7.5, 9.0 and 9.5 MeV. Thirty-seven spin-parity combinations for ⁵⁶Co excited states have been deduced. Previous J^π ambiguities for 11 of these states have been eliminated, and results in conflict with existing assignments for the levels at 3.235 and 3.378 MeV have been obtained. A search for 0⁺ states was carried out from angular distribution measurements at forward angles of the unpolarized (d, α) reaction. The combined results from this and previous experiments were found to be in reasonable agreement with calculated level schemes.     

Deuteron scattering on <Superscript>6</Superscript>Li at an energy of 25 MeV

At an energy of 25 MeV and in the angular range 7°−175° in the laboratory frame, angular distributions were measured for elastic deuteron scattering on ⁶Li nuclei and for the respective inelastic-scattering processes accompanied by the transitions to the ground state (1+) of the ⁶Li nucleus and to its excited state at E _x = 2.186 MeV (J ^π = 3⁺). The resulting data were analyzed on the basis of the optical model of the nucleus and the coupled-reaction-channel method with allowance for the mechanism of alpha-particle-cluster exchange. It is shown that only upon including, in the analysis, channel coupling and the exchange mechanism can the experimental cross sections for elastic and inelastic scattering be reproduced over the entire range of angles.     

Evidence for twoρ′ (1600) resonances

The data on the reactionse ⁺ e ^?→π ⁺ π ^?, 2π ⁺2π ^?,π ⁺ π ^? π ⁰ π ⁰ andγp ⁺ γ ^? p, 2γ ⁺2γ ^? p,γ ⁺ γ ^? γ ⁰ γ ⁰ p are analysed. It is found that to obtain a consistent picture it is necessary to postulate two vector resonances with masses of 1.465±0.025 GeV and 1.700±0.025 GeV with widths of 0.235±0.025 GeV and 0.220±0.025 GeV respectively. A key feature in correlating all the data is the importance of off-diagonal terms in the photoproduction of states withJ ^p =1^? and a contribution from states withJ ^P ≠1^?. The results are compatible with thep-wave ππ scattering amplitude.     

The Jπ = 3− doublet at Ex = 6241 keV in 18F: Isospin mixing

The resonance previously observed at E_x = 6241 keV in the reactions ¹⁷O(p, γ)¹⁸F and ¹⁴N(α, γ)¹⁸F has been found to be a closely separated doublet (ΔE_x = 2.09±0.04 keV). Resonance strengths in ¹⁷O(p, γ)¹⁸F, ¹⁷O(p, α)¹⁴N and ¹⁴N(α, γ)¹⁸ have been measured and partial widths for the resonance states have been obtained. The doublet was further investigated by means of the ⁴He(¹⁴N, α)¹⁴N reaction using the differentially pumped gas target at CRNL. Analysis of these data using R-matrix theory yielded J^π = 3^? for both states and more precise values of the α-particle widths (Γ_α(lower) = 133 ±4 eV; Γ_α(upper) = 137 ±4 eV). The reduced α-particle widths and the E1 and M1 transition strengths indicate that the doublet arises from the nearly complete mixing of T = 0 and T = 1 eigenstates which in the absence of an isospin breaking interaction would have been separated by less than 40 eV. The α-particle scattering experiments included the J^π = 1⁺ resonance at E_x = 6257 keV and yielded the new values of Γ_α = 580±12 eV and Γ_p = 25⁺³⁵_?25 eV.     

Study of the diffraction scattering 12C + 12C with the excitation of the 12C exotic state 0 2 + (the Hoyle state)

New results from a series of experiments dedicated to the study of the ¹²C exotic state (the so-called Hoyle state) are presented. In spite of the many investigations that have been carried out, the structure of this state (which lies above the threshold for breaking up into three alpha particles) is still unknown. The different models assume that the nucleus has an abnormally large size in this excited state. However, until recently, methods for measuring the radii of unbound states have not been suggested. The best way to solve this problem seems to be by measuring the angular distributions of elastic and inelastic scattering of ¹²C on different target nuclei, and the determination of the radii is based on the fact that, at small scattering angles, the cross sections for direct reactions at high enough energies behave like Frauenhofer diffraction on a black ball. Accordingly, an experiment was performed aimed at measuring the elastic and inelastic angular distributions of ¹²C with an energy of (121.5 ± 0.5) MeV on a ¹²C target. The elastic scattering was measured in the angular range from 18° to 50° in the c.m. system with uncertainty in the angle of measurement equal to Δθ = ± 0.6°. The inelastic cross section was measured for the ¹²C excited state 2⁺ (4.44 MeV) and 0⁺ (7.65 MeV). Estimates were made for the diffraction radii for the ground and excited states. An increase was observed in the radius of the state at 7.65 MeV compared to those of the ground and first excited states.     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

Λ, Λ production in e+e− annihilation at 33 GeV centre of mass energy

Performing a PWA of the π^?π^?π⁺ system over the ^?tp/p range 0.2 to 0.4 GeV² we find evidence for a J^P = 0^? ,J^G=1^? meson of mass 1342 ± 20 MeV and width 220 ±70 MeV decaying into ?π. This state is produced by natural parity exchange with a slope similar to that of elastic scattering. It can be interpreted as a radial excitation of the π meson (π′).     

Isobaric analog resonances in the 82se+p system investigated by (p,p'γ) angular correlations and low-lying states in 83Se

Low-lying states in ⁸³Se have been studied through proton-induced isobaric analog resonance (IAR) reactions. Excitation functions for elastic and inelastic proton scattering were measured in the bombarding energy range 4.5– to 7.7 MeV. Angular distributions of proton inelastic scattering cross sections for the reaction ⁸²Se(p, p')⁸²Se(0.655 MeV 2⁺) and angular correlations of the inelastic protons and the associated 2⁺-0⁺ de-excitation γ-rays were measured on observed resonance peaks. In the analysis for the inelastic scattering, direct reaction contributions to the IAR were taken into account. Correlations between the low-lying states in ⁸³Se and the excited 2⁺ core state are discussed.     

12C induced transfer reactions on 56Fe

Transfer reactions ⁵⁶Fe(¹²C, xN) have been investigated. Angular distributions of particles following elastic scattering, one neutron and one proton transfer reaction channels leading to low lying states in respective residual nuclei have been measured. These are analysed using the coupled reaction channel (CRC) formalism. Starting with a double folded real potential, the elastic scattering angular distribution is calculated using the computer code FRESCO. Inclusion of couplings to first excited states in both the target and the projectile already tends to describe the experimental elastic scattering distribution. Additional coupling of one neutron transfer reaction to first five excited states in ⁵⁵Fe and one proton transfer reaction to first three low lying states in ⁵⁷Co improves fit to the elastic scattering angular distribution. Further refinement in fit is brought about by addition of a weak imaginary potential to the complex potential calculated by ERESCO to simulate the absorption effects due to those channels whose coupling is not included explicitly. Such a potential describes the experimental angular distributions for elastic, one neutron and one proton transfer channels correctly in shape and magnitude without any arbitrary normalisation.     

Backward πd scattering between 140 and 260 MeV

Differential cross sections for elastic scattering of pions by deuterons have been measured for centre-of-mass angles between 130° and 175°, and at laboratory energies 141, 177, and 260 MeV for π⁺, and at 151, 185, and 189 MeV for π^?. At 177 and 260 MeV the cross sections are a factor of 2 lower than the predictions of three-body theories.