Investigation of excited states in56Co with the54Fe(3He,pγ)56Co reaction

The two-particle stripping reaction⁵⁴Fe(³He,p γ)⁵⁶Co at \(E_{3_{He} } \) =15.15 MeV was used to investigate theγ-ray transitions and to determine branching ratios, possible spin assignments and mean lifetimes of levels in⁵⁶Co up to 5.5 MeV excitation energy. Gamma-rays for both angular correlations and lifetime measurements were observed with a 43 cm³ Ge(Li) detector in coincidence with proton-groups detected at 0°. The level scheme and lifetime values are compared with the predictions of various shell model calculations.     

Investigation of α-nucleus interaction in the 27Al (α,α)27Al scattering and 27Al (α, d )29Si reaction

Full finite-range macroscopic calculations in the distorted-wave Born approximation have been performed using the molecular and Michel α-nucleus potentials to analyze the angular distributions of cross-sections of the ²⁷Al(α, d)²⁹Si reaction, at 26.5 and 27.2 MeV incident energies, leading to seven transitions up to the excitation energy E _X = 4.08 MeV of the final nucleus. The parameters of the two types of the α-nucleus potentials are determined from the elastic-scattering data. Both the molecular and Michel potentials, without any adjustment to the parameters needed to fit the elastic-scattering data, are able in most cases to reproduce, simultaneously, the absolute cross-sections particularly at large angles, where the previous calculations failed to reproduce by orders of magnitude, and the gross pattern of angular distributions of the reaction. The deuteron-cluster spectroscopic factors for most of the seven transitions, deduced using the two α-²⁷Al potentials, differ from those obtained in earlier works. The spectroscopic factor for the ground-state transition, deduced in the present work for the 25.8 MeV data, agrees well with the shell model prediction. Received: 15 July 2002 / Accepted: 8 August 2002 / Published online: 10 December 2002 RID="a" ID="a"e-mail: akbasak2001@Yahoo.com Communicated by G. Orlandini     

Properties of some resonances of the 55Mn(p,γ)56Fe reaction in the E p = (1.3−1.8) MeV region

Radiative decay of 21 resonances in the ⁵⁵Mn(p, )⁵⁶Fe reaction was studied in the proton beam energy region E _p = (1.3–1.8) MeV. Branching of decay to many low lying bound states up to excitation energy E _x 8 MeV was measured. Exact energy of all resonances has been established, what pointed out that five of the resonances are very close doublets. For all studied resonances their spin-parity characteristics were determined. Assignment of some resonances as isobaric analogues of the states in the ⁵⁶Mn nucleus was discussed and short note about energy systematics of isobaric analogue resonances was given.     

High-spin states in206Bi populated in the205Tl(α, 3n) reaction

Using alpha-particles in the energy range 35–51MeV and in-beam gamma ray and conversion electron spectroscopy techniques the reaction²⁰⁵Tl(α, 3n)²⁰⁶Bi was studied. A 15±1ns isomeric 15⁺ state was found at an excitation energy of 3147keV in²⁰⁶Bi. The main configuration of the isomeric state is suggested to beπh _9/2 vp ₁ ^2/?1 i ₁₃ ^2/?2 . The isomeric state decays mainly through a stretched cascade of five gamma rays to the previously known 0.88ms 10^? state of theπh _9/2 vi ₁₃ ^2/?1 (j ^?2)₀₊ configuration at an excitation energy of 1045 keV. A shell model calculation of the yrast states has been performed and it is found that the calculation agrees fairly well with the experiments. The average deviation between experimental and calculated energies for the yrast states with angular momenta in the region 6–18 is +4keV and the root mean square deviation is 22 keV.     

Angular distributions of γ-rays from four resonances of the55Mn(p, γ)56Fe reaction

Four resonances in the⁵⁵Mn(p, )⁵⁶ Fe reaction at the centre-of-mass proton beam energy E _P ^CM =1320, 1504, 1508 and 1649 keV were studied. Angular distributions for some strong -rays following the radiative decay of the resonances were measured and analysed in terms of the channel-spin formalism. Spin-parity assignmentI _r =3⁺, 4⁺ and 3⁺ was acquired for the 1320, 1504 and 1649 keV resonances, respectively. No definite assignment was established for the 1508 keV resonance and the resonance is assumed to be a very tight multiplet. Analysis of primary transitions to bound states of the Fe final nucleus permited us to assign these states. The 2⁺, 2⁺, 2⁺, 6⁺ and 4⁺ assignments were ascribed to the states at excitation energyE _x =5705, 5303, 4738, 4692 and 4658 keV, respectively, while for the 5132 keV state ambiguous assignment 3⁺ or 4⁺ was found. Multipole mixing ratio was established for some primaries. The coupling of angular momenta of proton and target nucleus in the formation of the 3⁺ resonances was also roughly discussed.Participated partly in the course of his work on diploma thesis.The authors wish to thank the staff of the Van de Graaff accelerator at Charles University in Prague for the efficient operation of the machine. One of us (M. X. T.) acknowledges the staff of the Dept. of Nuclear Physics of Charles University, Prague, for the excellent working conditions.     

~(56)Fe(n,p)~(56)Mn反应截面测量

在E_n=12—18MeV,用活化法测量了~(56)Fe(n,p)~(56)Mn反应截面,在E_n=14.61±0.20MeV处做了绝对测量,结果为108.0±2.7毫巴.中子通量用伴随粒子法测定,并与反冲质子望远镜相比较,两种方法在1—2%的误差范围内一致.~(56)Mn的γ放射性用φ10×7.6厘米的NaI(Tl)闪烁谱仪测量,谱仪探测效率用4πβ-γ符合法标定的~(56)Mn标准源刻度.测量结果与现有数据进行了比较.     

Key resonant states in the8Li(α,n)11B reaction in the inhomogeneous big bang models

The resonant states in the key reaction⁸Li(,n)¹¹B for the inhomogeneous Big Bang Models were studied experimentally through the⁹Be(,p)¹²B reaction at 64 MeV. This reaction is found to excite all the resonances of interest in¹²B. The most crucial resonant state at 10.572 MeV in¹²B (0.572 MeV above the threshold) was found to have _tot20±10 keV and J=(1^–), suggesting that the S-factor of the (,n) process should be larger than that obtained before.     

Hamilton–Jacobi equation,reaction action surface and the emergence of the force concept in chemical reaction dynamics

A combination of Hamilton–Jacobi equation and fast marching algorithm can be used to study reaction dynamics by converting the potential energy surface to a reaction action surface. The reaction action surface has been found to be an important tool in theoretical chemistry, allowing us to provide a different force-based perspective of chemical reactions. Several properties such as reaction force, reaction force surface, reaction path force and reaction path force constant have been defined and calculated by using the reaction action surface. This paper investigates these newly defined properties in order to understand the role they play in chemical reaction with reference to a model 4-well potential energy surface.     

Properties of Some Bound States of the 56Fe Nucleus Excited by the 55Mn(p,γ)56Fe Reaction

Radiative decay of 21 resonances in the ⁵⁵Mn(p,)⁵⁶Fe reaction was studied in the proton beam energy region E _p = (1.3-1.8) MeV. Properties of bound states in the final ⁵⁶Fe nucleus have been deduced from accurately measured very complex -ray spectra. About 150 levels have been firmly established for excitation energy up to 8 MeV and 93 of them have been observed for the first time or their established energy is substantially more accurate than in former publications or some other information is new. For each of the 57 levels, there has been established its decay and firmly observed at least one decay branch. Spin and parity have been newly determined or appreciated for 35 levels and for 35 levels the mean lifetime has been newly established by the DSAM method. Crude comparison of the observed level density with the statistical Fermi model prediction has been also performed.     

18F production in the 19F(γ, n) reaction

A race-track microtron is used to measure the yield of ¹⁸F in the reaction ¹⁹F(γ, n) at an energy of the electron beam of 55 MeV. ¹⁸F is widely used in positron emission tomography for high-sensitivity diagnostics. The currently available data are not sufficient to make accurate estimates of the yield of ¹⁸F in isotope production experiments using the reaction (γ, n). The value of σ^?1 estimated in this work is (1.7 ± 0.1) mb.     

Angular distributions of electrons in the (γ, 2e) reaction andee-correlations in the atom

The cross sectionsd ³ σ/dE ₁ d n ₁ d n ₂ for the Ar (γ, 2e) Ar⁺⁺ process are calculated on the basis of the diagram approach within the energy intervalω=400–650 eV as functions of the angleθ ₁₂ between final electrons with equal energiesE ₁=E ₂ for several levels of the final Ar⁺⁺ ion. It has been elucidated that the interference of amplitudes corresponding to the interaction in the final and initial states is of prime importance. The angular distributions over the angleθ ₁₂ are very sensitive to the term of the final ion. There are numerous data for the experimental verification of the theory, in particular, for the selection of leading diagrams. The (e, 3e) experiment is also desirable.     

Study of the187W states excited in the (n, γ) reaction

A singles-ray spectrum and a spectrum of summed amplitudes of coinciding pulses (SACP) were measured in the¹⁸⁶W(n, )¹⁸⁷W reaction experiment on the thermal neutron beam. It was for the first time that the data on¹⁸⁷W-transitions were obtained in the excitation energy region from 1500–2500 keV. The neutron binding energy was determined to beB _n=5467.25 (4) keV (statistical error only). In result the level scheme of¹⁸⁷W was developed in the excitation energy interval 1E _f < 3.4=" mev,=" which=" contained=" 105=" levels=" with=" about=" 70=" of=" them=" being=" identified=" for=" the=" first=" time.=" the=" experimental=" values=" for=" summed=" intensities=" of=" two-step=" cascades=" were=" established=" to=" exceed=" those=" predicted=" by=" the=" modern=" statistical=" theory=" (by=" 36±6%).=" this=" is=" explained=" by=" a=" considerable=" contribution=" of=" few-quasiparticle=" components=" to=" wave=" functions=" of=" compound=" and=" intermediate=">     

New findings in the Fe—Ni invar spin dynamics

Certainty in the spin wave stiffness D₀ was achieved for the first time in the problem of invars under Fe-Ni alloy polarized neutron scattering. A temperature power dependence of stiffness D = D₀Τ^X, with x ?0.5, was obtained for the entire ferromagnetic region Τ = 1 — T/T_c, from Τ = 0.1to Τ = 0.9. The spin stiffness was found to be D₀ = 137 meVŲ. Possible causes of scaling dependence CD(T) are discussed.     

Energy deposition and GDR emission in the reaction 209Bi(α,α′) at 240 MeV

Neutron fold distributions measured for the reaction ²⁰⁹Bi(α,α′) at 240 MeV have been analyzed with the help of Statistical Model calculations to determine the distribution of excitation energy, E_x, in the primary target fragments as a function of the projectile energy loss, EL. The reconstructed distributions in excitation energy feature a plateau which extends from the kinematical limit E_x = EL to very small excitations, indicating a variety of interactions of the beam particles with the target nucleus. The requirement of an additional coincidence with a light charged particle leads to the selection of a significant higher average excitation energy. Those results are extrapolated to explore the effects of including the excitation energy distributions in the analysis of previous GDR measurements in ²⁰⁸Pb. Corrections of the derived GDR parameters due to the partial transfer of excitation energy are suggested.     

Study of the reaction 12C(γ, n 3He)2α

The possibility of separating, with the aid of photoemulsion, channels of the reaction ¹²C(γ, n ³He)2α that involve the formation of ⁷Be and ⁸Be intermediate nuclei in excited states is studied. The experimental energy distributions of these nuclei are obtained. The relative yields from these reaction channels are estimated.     

Study of 113Cd by the 110Pd(α,nγ) reaction

The nuclear structure of ¹¹³Cd was studied using in-beam γ-ray spectroscopy. A level scheme, consisting of 65 levels and more than 100 transitions, was constructed on the basis of γγ coincidences using five compton-suppressed Ge detectors. Spins were assigned by means of excitation function slopes and angular distribution analysis. The resulting level scheme was interpreted in the framework of the interacting boson-fermion model.     

Triple correlation in the 10B(n, αγ)7Li reaction

The formally T-odd triple correlation between the directions of the momenta of α particle and γ quantum and the polarization pseudovector of a thermal neutron was examined for the ¹⁰B+n=⁷Li+⁴He+γ reaction. Such T-odd correlations can be directly used for checking time reversal invariance in the elastic scattering of particles. In more complex reactions, this correlation can occur as a result of particle interactions in the entrance and exit channels of the reaction and, being a background effect, requires correct theoretical or direct experimental estimation. Our experiments gave an upper limit of 3.2×10^?4 (90% confidence level) for the possible T-odd asymmetry parameter in the reaction under study.     

Investigation of 238U in the (n,n′γ) reaction

An irradiation of ²³⁸U with a beam of reactor fast neutrons permits revealing about 550 gamma transitions associated with the respective (n, n′γ) reaction and with fission fragments. The use of all known data on gamma radiation from fission fragments makes it possible to identify gamma transitions belonging to ²³⁸U with a high probability. The scheme of levels and gamma transitions is composed for ²³⁸U. New levels (including those of spin-parity J ^π = 0⁺) at excitation energies below 2 MeV are proposed. The low-lying levels in the rotational band for two-phonon octupole excitations are determined. It is found that a hybrid state is formed upon the crossing of this band and the band based on two-quasiparticle excitations. This hybrid state must involve excitations of both types. A small value of the rotational-band parameter in the isomer of energy 2559.0(4) keV is explained by the contribution to this state from two-quasiparticle configurations belonging to the 1k _17/2 subshell. The same circumstance may also be responsible for an enhanced yield of ternary fission for this isomer.