A study of the 35Cl(p, γ)36Ar reaction and the energy levels of 36Ar

Proton energies and strengths of (p,γ) and (p, p₁) resonances of the ³⁵Cl + p reaction were determined for E_p = 0.4?3.0 MeV and 1.9?3.0 MeV, respectively. The γ-decay of 84 resonances was studied with a 40 cm³ Ge(Li) detector. The branching ratios and excitation energies of 38 bound levels were determined. A new bound level was observed at E_x = 8472.0 ± 1.0 keV. Doppler-shift attenuation experiments yielded lifetimes of 20 bound levels. Spins and/or parities for bound levels and resonances were derived on the basis of observed transition strengths.     

Energy levels of 37K

Angular distributions have been measured for six ³⁶Ar(p,γ)³⁷K resonances in the E_p = 0.9−3.0 MeV energy region. These experiments yield spin- and parity assignments to seven excited states of ³⁷K, γ-ray branching ratios for each state, together with the multipolarity mixing ratios of most transitions. Lifetimes have been deduced from the same data with the DSA method.Excitation energies have been determined with a precision up to 20 eV. A resonance- and excitation-energy measurement at the E_p = 918keV resonance yields a ³⁶Ar(p, γ)³⁷K Q-value of Q = 1857.57 ± 0.09 keV.The ³⁶Ar(p, p₁γ) yield curve, measured in the E_p = 2.6–3.3 MeV region, yields additional information on resonance and excitation energies of ³⁷K states with a typical precision of 0.6 keV.The new data on ³⁷K levels allow a detailed comparison of the level schemes of the mirror nuclei ³⁷Ar and ³⁷K. The present experimental data agree quite well with the results of previous shell-model calculations.     

Étude des États excités du 33Cl à l′aide de la réaction 32S(p, γ)33Cl

Energies and strengths of resonances of the ³²S(p, γ)³³Cl reaction were determined in the range E_p = 0.4 ? 2.6 MeV. Three new resonances were observed respectively at E_p = 1588, 1748, 1880 keV and the doublet of resonances at E_p ≈ 1900 keV was clearly shown. The (p, γ) strengths of resonances at E_p = 422, 580, 588, 721 and 2577 keV were measured with a 80 cm³ Ge(li) detector. The Q-value of this reaction and the energies, γ-ray branchings and mean lifetimes of levels were determined. The spins and parities of the E_x = 2.35, 3.82, 3.97, 3.98, 4.78 MeV levels have been measured. A comparison of γ-ray transition strengths with mirror transitions and with model predictions is made.     

Étude des états excités du noyau 34Cl: (I). Courbe d'excitation de la réaction 33S(p, γ)34Cl, énergies,rapports d'embranchement et vies moyennes des niveaux du 34Cl

Resonance energies and strengths are reported for forty-five ³³S(p, γ)³⁴Cl resonances in the range E_p = 1.0–2.0 MeV. Analysis of the γ-ray spectra by means of two Ge(Li) detectors leads to precise excitation energies of bound states and branching ratios of resonant levels and bound states. New bound levels are found. The reaction Q-value is 5140.3 ± 1.5 keV. Mean lives (or limits) of twelve bound states of ³⁴Cl have been obtained from DSA measurements at seven of the studied ³³S(p, γ)³⁴Cl resonances.     

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.     

Investigation of 36Ar with the 35Cl(p, γ)36Ar reaction: (II). Angular distributions and shell model calculations

The angular distributions of primary and secondary γ-ray transitions at eight resonances in the ³⁵Cl(p,γ)³⁶Ar reaction have been measured with a 60 cm³ Ge(Li) detector. The measurements lead to unambiguous J^gp assignments for 17 states of ³⁶Ar and to J^π limitations for seven other states. A large number of γ-ray multipole mixing ratios were obtained. Many of the resonances are analogues of ³⁶Cl levels. The lifetime of the E_x = 6.36 MeV level has been determined as τ_m = 440 +-150 fs. A simple shell model calculation has been performed to study the odd-parity levels of ³⁶Ar and ³⁶Cl. Coulomb displacement energies have been computed. Spectroscopic factors have been calculated and compared with the experimental data for the ³⁵Cl(d, p)³⁶Cl and ³⁵(τ, d)³⁶ reactions.     

Spin assignment to the 9.026 MeV resonance level of36Ar using35Cl(p, γ)36Ar triple angular correlation measurements forE p = 533 keV

Triple correlation experiments have been performed to study the³⁵Cl(p, γ)³⁶Ar resonance for a proton energyE _p = 533 keV. From the analysis of the measured gamma ray angular distributions, due to the gamma decay of the 9.026 MeV resonance level in³⁶Ar via the 9.026 MeV→1.97 MeV→0 MeV double cascade, a spin value ofJ ₁ =2⁺ for the 9.026 MeV level and a mixing ratio of ?1.97 MeV∥L′₁ = 2∥9.026 MeV?/?1.97 MeV∥ L₁ = 1∥9.026 MeV? = ?0.055 + 0.022 for the 9.026 MeV→ 1.97 MeV transition could be derived.     

Study of the36Cl(n,p)36S reaction in the neutron energy range up to 10 keV

The³⁶Cl(n,p)³⁶S reaction cross-section was measured by the time-of-flight method in the IBR-30 pulsed reactor of the JINR. The measured cross-section shows three not previously observed neutron resonances with energies E_n = 1.3; 3.5 and 8.2 keV for which the parameters A_p=gΓ_nΓ_p/Γ: 0.07 ±0.01; 0.08 + 0.03 and 1.7 + 0.3 eV were determined, respectively. Comparison of these results with the excited states obtained by the³⁶S(p, γ)³⁷Cl reaction made possible a more exact determination of the scale energy of the³⁷Cl nucleus excited states.     

(p, γ) Resonance strengths in the s-d shell

The strengths of selected resonances in the range E_p = 0.5–2.0 MeV in the (p, γ) reactions on Mg, ³⁰Si, ³⁴S, ³⁷C1, ³⁹K and ⁴⁰Ca have been found relative to the E_p = 632 and 992 keV resonances in ²⁷Al(p, γ)²⁸Si by relative yield measurements. Targets were made from mixtures or chemical compounds such that each contained at least two of the isotopes of interest and their chemical composition was determined by Rutherford back-scattering of α-particles. Absolute measurements were conducted on the selected resonances in ²⁷A1(p, γ)²⁸Si and ³⁰Si(p, γ)³¹P by semi-thick target and thin target techniques with the target thickness, needed for the latter technique, found by Rutherford back-scattering of protons. Absolute strengths for all of the resonances treated, together with one from each of ²³Na, ³¹P and ³⁵Cl, reported in a previous paper, were deduced by normalizing to the absolute measurements on the Al(p, γ)²⁸Si resonances.     

Total strength of the magnetic dipole resonance in 37Cl and 39K

The γ decay of resonance-like structures observed in the ³⁶S(pγ)³⁷Cl and ³⁸Ar(pγ)³⁹K reactions in the range of energies E _p = 0.8–2.8 MeV of accelerated protons has been studied. The M1 resonance on the ground and excited states of ³⁷Cl and ³⁹K nuclei has been identified. The position of the centroid and the total strength of the M1 resonance on the ground state of these nuclei have been determined and explained taking into account pairing forces.     

States in 53Mn from the 52Cr(p, γ)53Mn reaction

Eight resonances have been observed in the ⁵²Cr(p, γ)⁵³Mn reaction between E_p = 0.90 and 1.03 MeV. Gamma-ray spectra have been accumulated at four of the resonances. Spin assignments have been made to the resonant states on the basis of the measured angular distributions of primary γ-rays. Excitation energies and γ-ray branching ratios have been determined for 36 levels between 2.0 and 5.6 MeV. Mean lives for nine of the states have been extracted by the Doppler shift attenuation method.     

Strengths of (p, γ) resonances in 33Cl, 35Cl and 28Si

Absolute strength measurements have been performed for the E_p = 580 and 588 keV ³²S(p,γ)³³Cl, E_p = 1214keV³⁴S(p,γ)³⁵Cl and E_p = 633 and 744 keV²⁷Al(p,γ)²⁸Si resonances with a Ge(Li) detector. Results are discussed with regard to the decay of isobaric analog resonances in ³⁵Cl and ³⁷Cl.     

The reaction 36(α, γ)40Ar: γ-transition properties of resonance and bound states in 40Ar

The El character of the de-excitation of the 9 to 10 MeV states in ⁴⁰Ar has been studied through the reaction ³⁶S(α, γ)⁴⁰Ar. Angular distributions and γ-yield asymmetries of primary transitions from the E_α = 2.35 to 3.50 MeV resonances have been measured. The Doppler-shift attenuation method was used to obtain the following lifetime values: 720 ± 120fs (E_x= 2.52 MeV), 89 ±17 (3.21), 90±17(3.511), 22 ±9 (4.33), and 105 ± 17 (4.60).     

Resonance structure in 15N(p,n0)15O in the region Ep = 8.5–19.0 MeV

Excitation functions at seven angles, covering the energy range E_p = 8.5–19.0 MeV, have been measured for ¹⁵N(p, n_o)¹⁵O using time-of-flight methods. Angular distributions were also measured at five energies. Activation methods were used to determine the total cross section below the excited-state threshold. Ten resonances were observed, four of which have also been found in ¹⁵N(p, γ)¹⁶O data. The energies, widths and nucleon widths have been extracted and are used, together with proton capture data, to derive radiative widths for certain levels.     

Isobaric analogue resonances in proton elastic scattering from 84Sr

The cross section for the reaction ⁸⁴Sr(p, p₀)⁸⁴Sr has been measured for proton energies in the range E_p = 4.18?6.73 MeV. Resonance parameters were determined for 15 isobaric analogue resonances. Spectroscopic factors calculated for the analogues by means of the R-matrix theory and the Green function method are compared with Spectroscopic factors determined from the ⁸⁴Sr(d, p)⁸⁵Sr reaction. Angular distributions were measured at E_p = 7 and 12 MeV in order to obtain optical model parameters.     

Proton induced resonances on 21Ne

Excitation curves for the ${}^{21}\text{Ne}\text{(}\text{p}\text{, γ)}{}^{22}\text{Na}\text{,}{}^{21}\text{Ne}\text{(}\text{p, p}\text{′γ)}{}^{21}\text{Ne and}{}^{21}\text{Ne}\text{(}\text{p, p}\text{)}{}^{21}\text{Ne}$ reactions have been obtained for E_p = 0.4–1.6 MeV. Neon gas enriched to 92 % in ²¹Ne was recirculated in a differentially pumped gas target system. The fifteen previously reported (p, γ) resonances were established and nineteen new (p, γ) resonances found. Anomalies in the elastic scattering yield were observed for fourteen resonances. The reported state at E_x = 7278 ± 7 keV in ²²Na was resolved into a doublet separated by 1 keV. All unbound states in ²²Na, observed previously in other reactions, have been confirmed as resonance states in the energy range covered, with the exception of the E_x = 7942 ± 7 keV state. The new E_p = 663, 694, 1235, 1432 and 1543 keV resonances correspond to new unbound states in ²²Na. Excitation energies, γ-ray decay schemes, resonance widths and strengths as well as limits on J^π assignments are reported for all the resonances. From the Coulomb excitation of the E_x = 350 keV, first excited state in ²¹Ne a value of B(E2) = 0.014 ± 0.002 e² · b² is deduced. The astrophysical as well as the nuclear structure implications of the present results are discussed.     

Widths of the 7.74 MeV analogue state in39K

The³⁸Ar(p, p)³⁸Ar and³⁸Ar(p, γ)³⁹K reactions have been investigated in the analogue resonance region at E_p=1.39 MeV. For the 7.74 MeV state of³⁹K branching ratios, unique spin and parity, \(J^\pi = \tfrac{3}{2} - \) , proton and total width, Γ_p=Γ=1.1±0.2 keV, have been determined.     

Gamma rays and neutrons following preequilibrium 165Ho(p, xcnypγ) reactions at Ep = 60 MeV

Neutrons and γ-rays following 60 MeV proton bombardment of ¹⁶⁵Ho were measured in coincidence with discrete γ-rays characteristic of the reaction channels (residual nuclei). The cross sections for the (p, xcnγ) reactions with x = 2–6, the γ-ray multiplicities, and the energy and angular distributions of the emitted neutrons were analyzed in terms of the preequilibrium and equilibrium deexcitation processes. Characteristic behaviours of the preequilibrium process were found in the (p, 2nγ) and (p, 4nγ) reactions where the sum E_T, = ∑^xE_i of the energies E_i of the emitted neutrons was large, while those of the equilibrium process were typical for the (p, 6ny) reaction with small E_T. The reactions are well reproduced by the expression σ. ≈0.35∑_xσ (2, x?2) + 0.4∑_xσ(1, χ?1)+ 0.25∑_xσ(0, x), where σ(n_p, n_c) stands for emission of n_p neutrons at the preequilibrium stage followed by evaporation of n_c neutrons at the equilibrium stage.     

Investigation of the reaction 34S(p, γ)35Cl: (I). Resonances at proton energies above 2 MeV

The yield curve of the reaction ³⁴S(p, γ)³⁵Cl has been measured over the energy range E_p = 1.95–2.91 MeV. Proton energies and strengths of 84 resonances are given. The decay schemes of 38 selected resonances have been studied, and for these branching ratios and spin limits are presented. The proton energy of the well known $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{?}}$ analogue resonance has been measured as E_p = 1211.45 ± 0.09 keV. The reaction Q-value is Q = 6371.6 ± 0.4 keV.     

Gamma-rays from the24Mg(p,γ)25Al reaction for proton energiesE p=800 keV toE p=1,830 keV

The yield curve and resonance strengths of resonances in the²⁴Mg(p, γ)²⁵Al reaction for the proton energy rangeE _p=800 keV toE _p=1,830 keV, have been determined and the existence of a resonance atE _p=1.184 MeV confirmed. Single energy spectra as well as decay schemes and branching ratios are given for these resonances. An upper level of 2.0×10^?15 sec for the lifetime of the 3.079 MeV level in²⁵Al results from a Doppler shift attenuation measurement carried out on the 2.624 MeV gamma line originating in the 3.070 MeV→0.455 MeV transition in²⁵Al.