Be9(d,p),(d,t),(d,a)反应研究

本文在E_d=0.1—2.5MeV能量范围内,研究了Be⁹(d,p₀)Be¹⁰(0),Be⁹(d,p₁)Be¹⁰(3.368MeV),Be⁹(d,t₀)Be⁸(0),Be⁹(d,α₀)Li⁷(0)及Be⁹(d,α₁)Li⁷(0.478MeV)诸反应。在E_d=0.150,0.220,0.401,0.706,1.005,1.301,1.484,1.750,2.000,2.250和2.500MeV共十一个能量上分别测量了这五群出射粒子在θ_L=10—155°区间的角分布。在θ_L=135°,E_d=0.1—2.5MeV,在θ_L=95°,E_d=0.1—2.2MeV,和在θ_L=112.5°,E_d=0.5—2.5MeV测量了Be⁹(d,p₀)Be¹⁰的激发函数。在θ_L=135°和112.5°,E_d=1.2MeV,用较厚靶(100—300μg/cm²)测量了Be⁹(d,p₀)Be¹⁰(0)反应的截面绝对值,结果为σ_(p0)(θ_L=135°)=1.60mb/sr,σ_(p0)(θ_L=112.5°)=1.55mb/sr。这样就得到了在此能区内,这五群出射粒子的截面情况。对所得结果进行了一些讨论。     

Statistical analysis of the (d,p) and (d,d) reactions on 40Ca

Excitation functions of the ⁴⁰Ca(d, p)⁴¹Ca and ⁴⁰Ca(d, d)⁴⁰Ca reactions have been measured at 45°, 90°, 135° and 170° from E_d = 4.50 to 5.43 MeV in 10 keV steps. Angular distributions of these reactions have been taken at E_d = 4.70, 5.00 and 5.30 MeV from 25° to 170° in 5° steps. Transitions were observed to the excited states for the range 0.0 ≦ E_x ≦ 3.74 MeV in ⁴¹Ca. Rapid fluctuations in the excitation functions and strong variations of the angular distributions with the incident energy were observed, suggesting that the contribution from compound nucleus processes is very large. Various quantities extracted from the experimental data were compared to the predictions of the statistical theories combined with the DWBA theory for the calculation of the direct reaction amplitudes. The results of the present analysis are consistent with the predictions of the standard statistical theories based on the neglect of the channel-channel correlation.     

A study of the121,123Sb(p,d) reactions

Levels of^120,122Sb have been observed using the^121,123Sb(p, d) reactions atE _p = 26.2 MeV. Thirty-two levels of¹²⁰Sb and thirty-four levels of¹²²Sb are observed below 2.0 MeV excitation with an energy resolution better than 25 keV FWHM. Experimental angular distributions were compared to DWBA calculations in order to extractl-transfers and spectroscopic factors. Strong mixing between the 3s _1/2, 2d _3/2, 2d _5/2, and 1g _7/2 neutron orbitals is observed in both nuclei. Nuclear Reactions:^121,123Sb(p, d),E=26.2 MeV; measuredσ(E _d ,θ).^120,122Sb deduced levels,l,J,π, spectroscopic factors. Enriched targets, magnetic spectrometer.     

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.     

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.     

Excitation functions for48Ca(d,p)49Ca(0) in the rangeE d=3.0–5.5 MeV

Excitation curves for⁴⁸Ca(d, p)⁴⁹Ca(0) have been measured at 12 angles in the energy region from 3.0–5.5 MeV with the aim to investigate the charge exchange effect expected at the analogous (d, n) threshold opening at 4.3 MeV. A broad flat minimum is seen in the 165° excitation curve around this threshold which is however much less significant than the charge exchange cusps observed in theA ≈ 90 mass region. More significant structure is seen atE _d≈5 MeV which possibly may be connected with⁴⁸Ca(4.611) core excitation or due to an intermediate state in⁵⁰Sc.     

A study of the second excited state of8Be by the10B(d,α2)8Be-reaction

The second excited state of⁸Be has been studied by analysis of the coincidence spectra of the reaction¹⁰B(d, α)2α forE _d =1.0-2.0 MeV. The excitation energy was found to be 12.0±0.4 MeV, and the reduced width 0.85±0.12 MeV. Differential crosssections of the (d, α ₂)-reaction were deduced.     

A study of the (d, α) reaction in 56Fe at 12 MeV

The (d, α) reaction in ⁵⁶Fe is studied at E_d = 12 MeV and angular distributions of the α-particles are obtained over the angular range 13°–83° (c.m.s.); the results are analysed in terms of the DWBA theory of direct reactions using the two-nucleon pick-up mechanism of Glendenning. Spectroscopic information on ⁵⁴Mn levels up to 4.3 MeV excitation is obtained.     

Lifetime measurements in56Co with the58Ni(d, αγ)56Co reaction

The two-particle pick-up reaction⁵⁸Ni(d, αγ)⁵⁶Co atE _d =7.0 MeV was used to determine mean lifetimes of levels in⁵⁶Co up to 2.73 MeV excitation energy by the Doppler shift attenuation method,γ-rays were observed in a 43 cm³ Ge(Li)-detector at 90° to the beam axis in coincidence withα-particles detected in two 200 μm-silicon surface barrier detectors atΘ _α =±55°. Mean lifetimes for 10 levels in⁵⁶Co and two lifetime limits have been obtained usingF(τ)-curves calculated with the Winterbon theory. The experimental results are compared with the predictions of recent shell model calculations.     

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.     

Deuteron elastic scattering and (d,p) reactions on 208Pb at Ed = 22 MeV and j-dependence of T20 in (d,p) reaction

An experimental study of deuteron elastic scattering and (d,p) reactions at E_d = 22 MeV was made for ²⁰⁸Pb target. A new j-dependence of T₂₀ for (d,p) reaction at backward angles was observed. A “model independent” optical potential method was applied to analyze deuteron elastic scattering in the 10–22 MeV energy range. A continuum discretized coupled channels (CDCC) analysis was performed for deuteron elastic scattering at 22 MeV and the deuteron breakup effect was elucidated. DWBA and CDCC (d,p) analyses were made for (d,p) reactions.     

Investigation of low-lying states of 15N via 14N(d,p)15N reactions with vector polarized deuterons

Angular distributions of cross section and vector analyzing power have been measured for the ¹⁴N(d, p)¹⁵N reaction at E_d = 10 MeV for transitions to levels up to 8.6 MeV excitation in ¹⁵N. Distorted wave Born approximation calculations and calibration curves were used to determine total and orbital angular momenta and spectroscopic factors of the transferred neutrons. The results were compared with different theoretical approaches.     

Untersuchung der Niveaustruktur von53Cr und52Cr mit (d,d′) und (d,t)-Reaktionen

Angular distributions of deuterons and tritons from the reactions^52,53Cr(d,d),^52,53Cr(d,d′),^53,54Cr(d, t)^52,53Cr have been measured at E_d=11.8 to 11.9 MeV. The elastic scattering data have been analyzed in terms of the optical model. The (d, d′) and (d, t) data have been compared with DWBA calculations. Deformation parameters and spectroscopic factors have been extracted. The results are qualitatively discussed in terms of different nuclear models.     

Influence of shell effects on the angular distributions of fission fragments

A dynamical-statistical model is used to analyze the experimental angular distributions of fission fragments in the reactions α + ²³⁸U, ²³⁷Np at E _α = 20–100 MeV, as well as to determine the Am isotope fission probabilities and the shape isomer yields in the reactions d + ^242,240Pu at E _d = 20–30 MeV. Manifestations of shell effects are found in the fission barrier structure up to the excitation energies of 50–60 MeV.     

A study of excited states of5He by the7Li (d, α)5He-reaction

The interactions of deuterons with⁷Li, in which two α-particles and a neutron are produced in the final state are studied atE _d =1.2 MeV. The dual parameter α-α coincidence spectrum was analyzed with a search program. The results indicate two excited states of⁵He: One at excitation energy 2.9±0.1 MeV and with a reduced width of γ²=1.1±0.4 MeV, and the other at 4.8±0.4 MeV, with γ²=0.9±0.4 MeV. No contributions of sequential decay through the 4⁺ state in⁸Be or direct three body decay was observed.     

12C(d, α2)10B and isospin violating two-step reactions

A model-independent S-matrix analysis for the isospin violating ¹²C(d, α₂)¹⁰B(E_x = 1.74 MeV) reaction was performed and the results compared to a recently published two-step coupled channels calculation. There are multiple solutions to the S-matrix fits. but it is found that none of the possible solutions are compatible with the partial-wave decomposition based upon the two-step mechanism. The data are satisfactorily fitted with a sum of Breit-Wigner resonances. When a non-resonant background is included in the calculation the result indicates that the magnitude of such a contribution is less than 2 % of the measured total cross section at E_d = 15 MeV and is consistent with zero. The reaction is therefore interpreted to proceed almost entirely through the compound nucleus.     

On the Existence of the Anomaly in the2 H(d,n) and2 H(d,p) Reactions atE d ≈100 keV

All data which are concerned with the existence of an anomaly in the excitation functions of the² H(d, n)- and² H(d, p)-reactions nearE _d =100 keV are discussed. New experimental data for the² H(d,p)- reactions using tensor polarized deuterons (90≦E _d ≦190 keV) are presented.     

Non-statistical effects in the 12C(12C, α)20Ne reaction near Ec.m. = 15 MeV

The ¹²C(¹²C, α)²⁰Ne reaction is studied near E_c.m. = 15 MeV. Angular distributions for three energies and excitation functions at θ_{lab = 30°} over an energy range E_c.m. = 14.5?15.4 MeV for about 20 levels in ²⁰Ne (E_ex = 0–13 MeV) are examined. The statistical analysis yields the results that a correlated resonance is present at E_c.m. = 14.75 MeV. A nonstatistical contribution to the reaction is also apparent when energy-averaged cross sections are compared with the Hauser-Feshbach model predictions. Strong population of the 0⁺₃ band in ²⁰Ne is observed.     

Five-nucleon transfer in the12C(d,7Li)7be reaction atE lab=78.0 MeV

Angular distributions of the¹²C(d,⁷Li)⁷Be reaction to the ground and to the unresolved first excited states of⁷Li or⁷Be nuclei were measured in the entire angular region in the centre of mass system atE _lab=78.0 MeV. Both the one-step five-nucleon cluster transfer as well as two-step sequential transfers were considered in the theoretical analysis. The former mechanism was found to dominate, but the latter is also not negligible.