High-resolution study of 49Cr through the (p,d) reaction

The ⁵⁰Cr(p, d)⁴⁹Cr reaction was studied at a bombarding energy of 55 MeV. Angular distributions were obtained for levels up to E_x = 10.5 MeV. The l-assignment was performed for each level and the spectroscopic factor was deduced by consulting the DWBA calculation. The strength distribution was obtained for l = 0, 1, 2 and 3. Many strongly excited states in the higher excitation region were identified as isobaric analog states (IAS) of ⁴⁹V. Fragmentation of the strength was clearly observed for these states. An accurate Coulomb displacement energy was obtained for each IAS by including the fragmented parts of the strength.     

A direct measurement of the total proton decay width of an isobaric analog state

Differential cross sections for the ²⁰⁸Pb (p, n) reaction populating the isobaric analog state (IAS) of the ²⁰⁸Pb ground state in ²⁰⁸Bi have been measured at a proton bombarding energy of 30.5 MeV. The experimental technique utilized the proton (p?) decay of the IAS to obtain neutron time-of-flight spectra. When these differential cross sections are compared to those obtained for the same reaction at 30.5 MeV using the pulsed-beam technique to obtain neutron time-of-flight spectra, the percentage of the IAS decay through p? channels is obtained. This comparison indicates that the p? decay of the IAS to the first three states of ²⁰⁷Pb accounts for almost all of the IAS width (0.97±0.28).     

Spin-parity assignments for the excited states of 91Nb from the 91Zr(p,nγ)91Nb reaction

The energy levels of ⁹¹Nb were studied by means of the (p, nγ) reaction. The de-excitation γ-rays were observed with a Ge(Li) detector in the proton energy range from 3.25 to 5.51 MeV in steps of about 30 keV. Resonances attributed to isobaric analog states in the compound system ⁹¹Nb were observed in the excitation functions of the de-excitation γ-rays. From an analysis of these analog resonances, a Hauser-Feshbach analysis and the γ-decay scheme, the spin-parities of the levels up to 2792.6 keV (22 levels) were assigned.     

Energy levels in 93Mo populated by the 93Nb(p,nγ) reaction

Energy levels of ⁹³Mo have been investigated by means of the ⁹³Nb(p, nγ)⁹³Mo reaction. The excitation functions of the level de-excitation γ-rays were measured with a Ge(Li) detector under proton bombardment in the energy range 3.0 to 5.0 Me V. A detailed γ-ray decay scheme which includes 69 levels and 123 γ-ray lines was constructed from the threshold energies for 64 γ-rays and the γ-ray excitation functions around five isobaric analogue resonances in the ⁹³Nb(p, nγ) reaction. Spin-parity values for 59 levels and favourable values for 8 levels were assigned from the analysis of relative neutron yields via the isobaric analogue resonances of the parent odd-odd nucleus ⁹⁴Nb. The results of the present experiment are compared with shell-model calculations.     

Investigation of isobaric analog resonances in 53Mn

The isobaric analog resonances in ⁵³Mn with different spins and parities are investigated by means of the ⁵²Cr(p, p), (p, p′), (p, p′γ), and (p, γ) reactions. Spectroscopic factors are derived and the experimental (p, γ) strengths are compared with theoretical single-particle estimations.     

Giant M1 resonance in the direct-semidirect model for nucleon radiative capture

The direct-semidirect model for nucleon radiative capture proceeding via giant E1 and E2 resonance states is extended to account for capture through collective M1 excitation. The ²⁰⁸Pb(N, γ₀) and ¹⁴⁰Ce(N, γ₀) reactions are investigated in the 2–10 MeV energy interval. For the M1 and isoscalar E2 neutron capture processes, calculations provide cross section values of the same order of magnitude, as well as comparable effects on γ-ray angular distributions. The model proves to be an appropriate framework for discussing the E1-M1 and E1-E2 interference processes, giving useful suggestions as to effects arising from the presence of the M1 and E2 collectivities.     

Proton-induced direct capture on 21Ne and 22Ne

The direct capture process in the reactions ²¹Ne(p, γ)²²Na and ²²Ne(p, γ)²³Na has been investigated at E_p = 0.3–1.6 MeV using neon gas enriched to 91 % in ²¹Ne and to 99 % in ²²Ne, respectively. The gas was recirculated in a differentially pumped gas target system of the extended-static and quasi-point supersonic jet type. For ²²Ne(p, γ)²³Na, the direct capture process has been observed to several final states in ²³Na up to E_x = 8.83 MeV excitation energy. The deduced spectroscopic factors C²S are in fair agreement with the corresponding values from stripping reactions. The capture transition into the ²³Na ground state exhibits broad structures, which resemble Ericson fluctuations. The data remove the previously reported discrepancies in C²S for the ²³Na ground state. The excitation functions for the ²¹Ne(p, γ)²²Na reaction are dominated by broad and intense resonances, which hampered the measurement of the direct capture process. The nuclear and astrophysical aspects of the results are discussed.     

Giant M2 and transversal E1 resonances in light nuclei

The cross section for inelastic backward electron scattering on 1p shell nuclei at incident energy E_e = 70 MeV is calculated in the shell model. Comparison is made with radiative pion capture and muon capture. It is shown that the T_> branch of the M2 resonance in (e, e') and the main maxima in the (π^?, γ) response function are formed by identical partial transitions. We consider the basic features of the M2 resonance excitation in 1p shell nuclei and predict configurational and isospin splitting of this mode.     

Energy levels of 92Nb and 94Tc from 92Zr, 94Mo(p,nγ)92Nb, 94Tc

The γ-decays of the energy levels of ⁹²Nb and ⁹⁴Tc were measured following the ⁹²Zr(p, n)⁹²Nb and ⁹⁴Mo(p, n)⁹⁴Tc reactions. For ⁹²Nb the γ-ray thresholds were measured and a detailed excitation function was obtained near the ⁹³Zr ground-state isobaric analog resonance. Also, γ-γ coincidence measurements with two Ge(Li) detectors were made for both ⁹²Nb and ⁹⁴Tc. The coincidence measurements determined ten energy levels in ⁹²Nb and two levels in ⁹⁴Tc. A comparison with particle transfer reactions is used to elucidate the structure of ⁹²Nb levels observed here but not seen in the transfer reactions.     

The reaction 35Cl(n,γ)36Cl studied with non-polarized and polarized thermal neutrons

The γ-radiation following capture of non-polarized and polarized thermal neutrons in ³⁵Cl has been investigated. Of the 420 γ-rays ascribed to the ³⁵Cl(n,γ)³⁶Cl reaction, 236 have been placed in a ³⁶Cl decay scheme. The branching ratios and the excitation energies (with 0.04–0.9 keV errors) of 72 bound states have been determined. Unambiguous spin assignments are given for 11 levels. The multipole mixing ratios for some primary γ-ray transitions have been determined. There exists a significant correlation between (d, p) stripping strengths and (n, γ) reduced primary transition probabilities for transitions to l_n(d, p) = 0 levels.     

The M1 strength distribution in the γ-decay of the gcase92 analogue state in 61Cu

The γ-decay of 26 resonances in the reaction ⁶⁰Ni(p, γ)⁶¹Cu in the range E_p = 3690–3790 keV has been investigated. The $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ isobaric analogue state (IAS) corresponding to the parent state at $\text{E}{}^1\text{= 2114}\text{keV}$ in ⁶¹Mi has been resolved into several fine structure components. The absolute strength for the transition to the antianalogue state is found to be Γ_γ = 0.24 ± 0.07 W.u. The measured M1 strength distribution for the decay of the $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$. IAS is compared to theoretical predictions.     

A model independent technique to determine relative proton strengths of isobaric analog states

The proton ($\text{p}$) decay of the isobaric analog state (IAS) of ²⁰⁸Pb has been observed in coincidence with the IAS neutron from the (p, n) reaction of ²⁰⁸Pb. Such a technique allows an accurate model-independent determination of the relative widths of the $\text{p}$ decay to the first three states of ²⁰⁷Pb, and, in principle, a much more accurate determination of the relative widths than either resonance or non-coincidence $\text{p}$-measurements.     

Proton capture by 176Yb in the giant dipole resonance region

The proton capture cross section for the reaction ¹⁷⁶Yb(p, γ)¹⁷⁷Lu has been measured for incident proton energies between 6 and 24 MeV. The excitation function for this deformed nucleus agrees remarkably well with the results of previous studies on spherical nuclei, e.g. ¹⁴²Ce(p, γ)¹⁴³Pr. The results indicate that the giant dipole resonance (GDR) is strongly excited as predicted by the direct-semidirect (DSD) model. It is found that the model describes reasonably well the excitation function. In the low-energy proton range, where the excitation function increases rapidly with proton energy, the observed cross section is significantly higher than the DSD predictions. The difference can only partly be explained by compound nucleus contributions. In the high-energy end, the predicted cross section tends to be too high primarily due to an increasing contribution of direct capture to orbitals with large angular momenta.     

^106,110Pd （p,nγ）^106,110 Ag reactions at Ep = 6.0 - 7.7 MeV

This paper reports that the experimental excitation functions of reaction （p,n） are measured for ^106pd and ^110pd at proton energy Ep = 6.1 - 7.5 MeV and Ep = 6.0 - 7.7 MeV respectively. The off-resonance excitation functions were compared with calculation values of the statistical model. A new formula used to estimate the peak cross section of isobaric analogue resonance was tested and it was found that calculation values agree reasonably well with the present data within experimental error, which confirms that the excitation strength of isobaric analogue state in （p,n） reaction not only depends on its spin, but also proportionally increases with the projectile proton spatial transmission Tp and the spectroscopic factor S for reaction （d,p） on the same target.     

Spin-isospin resonances: a self-consistent covariant description

For the first time a fully self-consistent charge-exchange relativistic RPA based on the relativistic Hartree-Fock (RHF) approach is established. The self-consistency is verified by the so-called isobaric analog state (IAS) check. The excitation properties and the nonenergy weighted sum rules of two important charge-exchange excitation modes, the Gamow-Teller resonance (GTR) and the spin-dipole resonance (SDR), are well reproduced in the doubly magic nuclei 48Ca, 90Zr and 208Pb without readjustment of the particle-hole residual interaction. The dominant contribution of the exchange diagrams is demonstrated.     

Particle coupling to the octupole state in 89Sr from 88Sr(p,p')88Sr analog resonances and 88Sr(d,p)89Sr

A study has been made of the six most pronounced isobaric analog resonances in the ⁸⁸Sr(p, p')⁸⁸Sr (3^?) excitation function at E_p = 7.65, 7.80, 7.92, 8.78, 9.75, and 9.90 MeV. They are believed to have a simple structure in the parent nucleus ⁸⁹Sr consisting of the lowlying positive-parity, single-neutron spectrum of ⁸⁹Sr weakly coupled to the collective 3^? state in ⁸⁸Sr. A high-resolution ⁸⁸Sr(d, p)⁸⁹Sr experiment was performed to locate small 2f and 3p admixed fragments in ⁸⁹Sr which would allow these analog resonances their entrance widths. In addition, on-resonance ⁸⁸Sr(p, p')⁸⁸Sr (3^?) angular distributions were measured in order to determine the partial waves involved in the exit channel. Results are compared to a particlephonon coupling model, and overall selectivity, strengths, and angular distributions of the (p, p') analog resonances are consistent with the above interpretation.     

Low lying states of 96Tc

The ⁹⁶Mo(p, n) and ⁹⁶Mo(p, nγ) reactions have been studied for proton energies between 3.8 and 5.5 MeV. Energy levels in ⁹⁶Tc up to 632 keV excitation energy have been determined. Possible spin and parity assignments are given for several levels based on the neutron enhancement and angular distributions observed on and off resonance of the $\text{5}\text{2}{}^{\mathrm{>+}}$ isobaric analog state in ⁹⁷Tc, as well as the observed γ-yields. The first excited state reported at 34 keV was found to be a close doublet only 0.8 keV apart. The observation of this doublet in the (p, n) reaction was used to determine the ground state Q-value Q = ? 3.760±0.010 MeV.     

Total (p,n) reaction cross section study on51V over the incident energy range 1·56 to 5·53 MeV

The total (p, n) reaction cross section for⁵¹V has been measured as a function of proton energy in the energy range 1·56 to 5·53 MeV with thick and thin targets. The fluctuations in the fine resolution excitation functions were analysed, to extract 〈Γ〉, the coherence width. The thick target excitation function suitably averaged over appropriate energy intervals has been compared with the optical model, Hauser-Feshbach and Hauser-Feshbach-Moldauer calculations. The strong isobaric analog resonance atE _p ～ 2·340 has been shape analysed to extract the proton width Γ _p , the spreading withW and the spectroscopic factor.     

Excitation functions and isobaric analogue states in the 55Mn(p, γ)56Fe reaction

Four excitation functions with proton energy range 1.3 to 1.85 MeV and γ-ray energy thresholds from 1.5 to 8.0 MeV were determined for the reaction ⁵⁵Mn(p, γ)⁵⁶Fe. Gamma-ray spectra were taken for two close-lying resonances at proton energies 1531 and 1537 keV. An analysis of the spectra suggests the spin-parity assignments for those two states to be 4⁺ and 2⁺, respectively, consistent with their being isobaric analogues to the close-lying third and fourth excited states in ⁵⁶Mn.     

The (p,nγ) reaction on Al and Si

The reactions ²⁷Al(p, n γ) ²⁷Si and ²⁸Si(p, n γ)²⁸P have been studied at E_p = 16 and 23 MeV, respectively, with a Ge(Li) detector in coincidence with a neutron detector. In ²⁷Si, two new γ-tran- sitions were detected and accurate excitation energies were determined. In ²⁸P, the γ-decay scheme was studied for the first time and new levels were located at 879 and 1602 keV excitation energy. For both nuclei the γ-ray spectra were supplemented by neutron time-of-flight spectra. The excitation energies are compared with those of the analogue nuclei and with the predictions from Coulomb displacement calculations.