Valence and inner proton hole states in119in via the (d,3He) reaction

Proton holes states have been studied up toE _x=17 MeV andE _x=3.5 MeV in the¹¹⁹In nucleus via the¹²⁰Sn(d,³He)¹¹⁹In reaction respectively atE _d=108.4 MeV andE _d=51 MeV. DWBA analysis of angular distributions has allowedl attributions for a large number of new levels and the determination of valence and inner hole strength distributions. The first 1g _9/2, 2p _1/2 and 2p _3/2 levels only exhaust 40%, 60% and 32% of their respective sum rule limits. The missing strengths are shared among several low lying levels and significant higher lying contributions. The 1f strength, not identified in the previous experiments is spread fromE _x=1 MeV to about 17 MeV. The low lying levels aroundE _x=2.4 MeV could exhaust some 40% of the 1f _5/2 sum rule. The higher lying strength with a flat maximum aroundE _x=7.5 MeV could account for the 1f _7/2inner hole strength and the missing 1f _5/2 valence strength. The experimental strength functions compare rather well with the predictions of the quasiparticle-phonon model.     

Untersuchungen zur Struktur des Kerns23Ne

Low-lying states of²³Ne up to about 3 MeV excitation energy have been investigated by studying the reactions²²Ne(d, p)²³Ne (E _d =4–6 MeV) and²³Na(n, p γ)²³Ne(E _n=8–9 MeV). From the (d, p) data,l-values and spectroscopic factors for the transferred neutron have been extracted by DWBA analyses. From the (n, p γ) data,γ-ray branchings and possible spin assignments have been derived. The results are used to discuss the applicability of the Nilsson model and the excited core model to the nucleus²³Ne.     

A study of17N levels andT=3/2 multiplets in mass 17 nuclei

Ten states of¹⁷N have been excited via the¹⁸O(d,³He)¹⁷N reaction atE _itd=52 MeV. Thel-transfer values are presented for eight of these states. Based on the subsequent spin and parity assignments severalT=3/2 isobaric multiplets are proposed.     

New aspects of the rotational model in25Mg

Spin assignments have been made to the²⁵Mg levels in theE _x=5–6 MeV region fromγ-ray angular distributions measured in the²²Ne(α, n y) reaction atE _α=8.0 and 8.8 MeV and fromp-γ angular correlations measured in the²⁴Mg(d, p γ) reaction atE _d=6 MeV. Unique spin assignments ofJ=7/2, 5/2, 5/2, and 9/2 could be made to the levels atE _x=5005, 5511, 5851, and 5967 keV, respectively. Ambigious assignments have been made to the levels atE _x=5245, 5524, 5785, 6032 keV (J=11/2, 7/2), 5455 keVJ=13/2, 9/2), and 5738 keV (J=3/2, 5/2). The present data confirm previous assignments ofJ=1/2 to the levels atE _x=5108 and 5466 keV, respectively. Lifetime estimates have been obtained, using the Doppler-shift attenuation method, for the levels atE _x=5245 keV (τ=30–60 fs), 5785 keV (τ=50–100 fs), 5967 keV (τ=50–100 fs), and 5455 keV (τ>1ps). All other levels in theE _x=5–6 MeV region haveτ<60 fs. A breakdown of theK-selection rule has been observed in theγ-decay of some high spin states, indicating a deviation from the strong coupling model.     

Half-life and magnetic moment of the 1+ first excited state in116Sb

The life-time and the magnetic dipole moment of the 1⁺ isomeric state in¹¹⁶Sb have been measured by the TDPAD method. The state was populated in the reaction¹¹⁶Sn(p, n)¹¹⁶Sb atE _p =15 MeV. The obtained results,μ(1⁺,¹¹⁶Sb)=+2.47(9) n.m. andT _1/2= 194(4) ns, support the pure single particle [πd _5/2*vd _3/2] configuration for the 1⁺ isomeric state.     

The structure of25Mg

Gamma-decay modes and spin(-parity) assignments of levels in²⁵Mg have been systematically investigated up to 10 MeV excitation energy by particle-γ-ray angularcorrelation measurements with the²⁴Mg(d, pγ) reaction at 6.5 MeV bombarding energy and with the²²Ne(α,nγ) reaction at 11.8, 12.5, 14.4 and 15.5 MeV bombarding energy. A level scheme has been established which is comprehensive up to 8.3 MeV excitation energy forI≦9/2 and up to 10 MeV for 9/2O d _5/2 — 1s _1/2-O d _3/2 shell and the unifieds-d shell Hamiltonian. The agreement is good to excellent. The first intruder states are located near 6.8 MeV excitation energy. The collective properties of²⁵Mg beyond the well established rotational bands are investigated using both the new experimental information and theB(E2)'s obtained from the shell model. The spectrum of²⁵Mg is completely rotational for the first five to six MeV above the yrast line. Shell modelB (M 1)'s reflect the Nilsson model structure of²⁵Mg in great detail. The prospectiveI ^π=9/2^?, 13/2^?, and 15/2^? members of the established negative-parity,K=1/2 band are found in levels atE _x=7801, 9410, and 8896 keV.     

Proton-hole states in 115In observed in the 116Sn(d, 3He) reaction

The ¹¹⁶Sn(d, ³He)¹¹⁵In reaction has been investigated at E_d = 50 MeV. Thirteen transitions to states up to 3 MeV excitation energy were studied. The measured angular distributions were compared with DWBA calculations and transferred angular momenta and spectroscopic factors were deduced. Levels at 1.04, 2.23 and 2.52 MeV were found to be excited most likely by l = 3 angular momentum transfer in contrast to previous investigations at lower incident energies in which no l = 3 transitions have been observed.     

A Study of the120Sn(p,nγ)120Sb reaction

Levels of¹²⁰Sb have been observed using the¹²⁰Sn(p, nγ) reaction at proton energies between 3.90 and 6.25 MeV. Sixteen previously unobserved levels below 1.03 MeV were populated. The resulting level scheme is compared with that obtained using the¹²¹Sb(p, d) reaction.     

Triple differential cross section for angle,atomic number and energy (or angular momentum transfer) calculated for the 280MeV40Ar+58Ni (or 365MeV63Cu+197Au) system in a simple model

Highly excited levels of³³S populated by α-particle capture in²⁹Si have been investigated forE _α=1.962 MeV to 4.287 MeV. Excitation curves measured with Ge(Li) and BF₃ detectors are reported. More than fifty resonances can be identified with levels in³³S. (α, γ) angular distributions measured on five strong resonances have yieldedJ ^π values 1/2+, 3/2 +, 5/2?, 5/2?, 5/2? and 3/2+ respectively, for theE _x =10.054, 10.466, 10.523, 10.721, 10.758 and 10.776 MeV levels in³³S. Elastic scattering experiments have been performed and theJ ^π assignments are found to be consistent with thel-values inferred from the elastic scattering data. Decay schemes from the above³³S levels have been proposed. A new level at 9.245 MeV is also suggested and theJ ^π values for the 4.425 and 2.87 MeV states are shown to be consistent with 7/2+ and 3/2+ assignment, respectively. Nuclear Reactions²⁹Si(α, γ) and²⁹Si(α, α),E _α=1.962-4.287 MeV. Measured relative σ(E). DeducedJ ^π andE _γ of³³S levels. New³³S level atE _x =9.245 MeV. Enriched targets.     

A comparative spectroscopic investigation of21Ne and21F by pickup reactions

The reactions²²Ne(d, t)²¹Ne and²²Ne(d, τ)²¹F have been investigated in a parallel experiment atE _d=52MeV. Energy spectra of tritons andτ particles have been measured up to excitation energies of 18MeV in both²¹Ne and²¹F nuclei. Thel values could be determined, and spectroscopic factors have been obtained by a DWBA analysis of the measured angular distributions. Together with the results from a preceding \({}^{22}Ne(\vec d, \tau ){}^{21}F\) experiment, several spins could be determined in²¹F. From a comparison of the triton andτ particle spectra,T=3/2 states in²¹Ne could be identified and on this basis the new information on spins of²¹F states could be transferred to their analog states in²¹Ne. The completeT _< andT _> parts of the (2s, 1d) strengths could be observed. The 1p strength is highly fragmented. Of theT _< part only 60% of the 1p1/2 and 40% of the lp3/2 strength could be found, but the totalT _> part of the 1p strength could be localized. The spectroscopic results for positive parity states are in qualitatively good agreement with shell model predictions.     

Level structure of 51Cr from the (d,p) reaction on 50Cr

The level structure of ⁵¹Cr is studied through the ⁵⁰Cr(d, p) reaction at E_d = 12 MeV using the Van de Graaff accelerator and multi-channel magnetic spectrograph at AERE, Harwell. A total of 174 levels was observed up to E_x ≈ 8.1 MeV. The stripping angular distributions are analysed in terms of the DWBA model with NLFR corrections. Spins, parities and spectroscopic factors are obtained for various levels and a sum rule analysis is made. Hauser-Feshbach calculations are done for the non-stripping levels and the levels showing a poor DWBA fit. Finally, the level spectrum is compared with the MBZ and MS models.     

Nuclear levels in152Eu

The transitional nucleus¹⁵²Eu has been studied using the (n, e), (n, γ), (n _res,γ), (n, γγ), (d, p), (d, t) and (p, d) reactions. The experiments have been performed at nine different laboratories. A model independent level scheme was established including 95 levels below 510 keV and nearly 900 transitions by combination of low energy transitions and reaction data. More than 20 additional levels result from gamma rays and/or charged particle reactions. The level scheme is interpreted in terms of the Nilsson model indicating that¹⁵²Eu is a deformed nucleus. Seven rotational bands and Nilsson configurations are established. An additional 27 rotational bands are tentatively or speculatively assugned. Gallagher-Moszkowski splittings are discussed. The neutron binding energy was determined as 6305.2±0.5 keV. The energy of the 9.3 h 0^? isomer is 45.599 keV. The lifetimes of four levels were measured. Nuclear Reactions¹⁵¹Eu(n,γ),E _n =thermal and resonance; measuredE _γ ,I _γ ,E _c.e.,I _c.e.,γγ Coinc.,γγΔt coinc.;¹⁵¹Eu(d, p),E=12MeV and 14MeV;¹⁵³Eu(d, t),E=12MeV;¹⁵³Eu(p, d),E =18MeV; deduced level scheme of¹⁵²Eu,J, π, T _1/2,cc, Nilsson configurations. Magnetic electron spectrometer, curved crystal spectrometer, Ge(Li) and Si(Li) detectors, magnetic spectrographs. Enriched targets.     

Groundstate proton radioactivity of nuclei in the tin region

Proton radioactivities with decay energies of (0.98±0.08) MeV and (0.83±0.08) MeV were produced by the fusion reactions⁵⁸Ni+⁵⁸Ni→¹¹⁶Ba ? and⁵⁸Ni+⁵⁴Fe→¹¹²Xe ?, and their halflives were measured to be (33±7) μs and (109±17) μs, respectively. The intensities of the lines correspond to production cross sections of about 30 μb and 40 μb. The two activities are assigned to the direct proton decay of¹¹³Cs and¹⁰⁹I. The measured halflives are compared with values calculated ford _5/2 andg _7/2 groundstates of¹⁰⁹I and¹¹³Cs and spectroscopic factors are deduced for the decays. An extensive search for the proton decay of¹⁰⁵Sb, produced in the reaction⁵⁰Cr(⁵⁸Ni,p2 n)¹⁰⁵Sb, had a negative result, excluding decay energies between 0.5 MeV and 1.5 MeV for halflives between 10 ns and 5 s.     

Structure of the mirror nuclei21Ne and21Na

Theγ-decay of levels in²¹Ne up to 10 MeV excitation energy has been investigated byn — γ coincidence measurements initiated with the¹⁸O(α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining then — γ angular correlation measurements performed atE _α=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleus²¹Na. The resulting values of E_x[keV]?J ^π are as follows: 4525-5⁺, 4686-3⁺, 5431-7⁺, 5549-3⁺, 5819-7^?, 6175-7⁺, 6268-9⁺, 6550-9, 6639-9, 7006-7⁺, 7041-9, 7356-7 or 9, 7422-11^(?), 7648-7⁺, 7981-11 or (7⁺), 8154-9, 8240-11, 8664-9^? or 11 or 13^?, 9401-13^?, 9867-13^? or 15⁺, 9941-13^? or 15 or 17⁺. The assignment of mirror levels in²¹Ne —²¹Na has been extended to the 6175 keV level of²¹Ne. Excitation energies, electromagnetic properties, Gamow?Teller matrix elements and spectroscopic factors of positive parity states are compared with the results of shell-model calculations which employ a unifieds—d shell Hamiltonian and the unrestricted configuration space of the 0d _5/2 —1s _1/2—0d_3/2 shell. Collective properties contained in shell model wave functions are explored up to the termination of bands atJ=17/2 or 19/2. The spectrum of intruder states in²¹Ne is observed to begin with a 5628 keV,J ^π=7/2⁺ state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands.     

A high resolution study of 26Al via the (p,d) reaction

Excitation energies and angular distributions of ²⁶Al levels in the first 6 MeV of excitation have been measured with the ²⁷Al(p, d)²⁶Al reaction at E_p = 35 MeV. Deuteron spectra were analyzed with an Enge split-pole magnetic spectrograph and recorded on nuclear emulsions (experimental resolution ≈ 6 keV, FWHM); supplementary data were recorded with position-sensitive wire proportional counters. The angular distributions were analyzed with the DWBA to extract the l-values and associated spectroscopic factors of the neutron transfers. The results for excitation energies, l-values, spectroscopic factors, and values of J^π, T are discussed in terms of previous experimental and theoretical work and in the light of new shell-model calculations for this system.     

Mechanism of reactions induced by 7 MeV deuterons on9Be [(d,p), (d,d), (d,t), (d,4He)]

Angular distributions of protons, deuterons, tritons and alpha-particles emitted from the reactions in thed+⁹Be-system atE _d =7 MeV as well as excitation functions at selected angles in the energy rangeE _d =6.5–7.5 MeV (LAB) were measured. The potential part of the elastic scattering is described by the phenomenological optical model. The compound nucleus contribution to all exit channels is determined using the Hauser-Feshbach model. The collective excitation of the 2.43 MeV excited state of⁹Be and transfer processes are analysed within the DWBA formalism. The analyses suggest a significant contribution of five-nucleon transfer to the (d,⁴He) channel.     

Elastic scattering of deuterons by 14C from Ed = 4 to 10 MeV

Angular distributions for the elastic scattering of deuterons by ¹⁴C were measured at nine energies between E_d = 4.2 and 10 MeV. Excitation functions were taken in 50 keV steps from E_d = 4 to 10 MeV. A resonance was observed at E_d = 4.5 MeV, which corresponds to an excitation energy of 14.41 MeV in ¹⁶N. An analysis using an optical model plus a single-level formula derived from the R-matrix formalism yields an l-value assignment of l = 4 for this resonance. Of the three J^π values allowed for l = 4 (J^π = 3⁺, 4⁺, 5⁺), the value of J_π = 3⁺ is found to be slightly preferred. Possible identification of this resonance with an analog in ¹⁶O is discussed. The angular distributions measured at off-resonance energies were analyzed with an optical-model potential which has a surface-peaked imaginary well. The energy dependence of the real and imaginary well depths are explicitly determined in the present work for E_d = 4 to 10 MeV. The best-fit optical-model parameters obtained from the present study are compared to those from the ¹⁴N(d, d)¹⁴N work.     

Mean field for the p+90Zr system in the energy range −60 MeV<E<+65 MeV and single-particle features of proton states in 90Zr from a dispersive optical-model analysis

Data on the scattering of protons with energies 5 MeV<E<65 MeV by ⁹⁰Zr nuclei and data on the energies of proton particle and hole levels in the A+1 and A?1 systems with A=90 are analyzed within the dispersive optical model. The parameters of the mean proton field for ⁹⁰Zr are determined in the energy range ?60 MeV<E<+65 MeV. The predicted single-particle features of the levels (root-mean-square radii of orbits, occupation numbers, spread widths, spectroscopic factors, and spectral functions) comply well with experimental data obtained in (d, ³He), (³He, d), (n, d), and (d, n) reactions for levels near the Fermi surface and in (e, e′p) and (p, 2p) reactions for deep levels.     

Shape coexistence and other aspects of nuclear structure in40Ar

Theγ-decay of⁴⁰Ar has been studied by particle-γ-ray coincidence measurements in the³⁷Cl(α, pγ) reaction at 12 and 13 MeV bombarding energy. Particle-γ-ray angular correlations and linear polarizations ofγ-rays were measured at 12 MeV. A lifetime measurement using the Doppler-shift attenuation method was performed at 11 MeV. The coexistence of spherical and deformed states in⁴⁰Ar could be concluded from the observation of aK ^π=0⁺ rotational band which has itsI ^π=0⁺ through 6⁺ members at 2,121, 2,524, 3,515 and 4,959 KeV excitation energy. The intrinsic quadrupole moment derived fromB(E2) values is ∥Q ₀∥=1,320 _?120 ⁺⁶⁰ mb. Negative-parity states with high spin were observed at 4,858(5^?), 4,494(5^?), 4,226(4^?) and 4,991 KeV(4^?) excitation energy. A complete account of all levels below 5 MeV excitation energy is obtained by a model in which twod _3/2 proton holes couple weakly to the⁴²Ca levels below 4.75 MeV excitation energy.