Excitation of isomeric states in the (γ,n), (n, 2n), and (γ, 2n) reactions on the 113In nucleus

The induced-activity method was used to measure the isomeric ratio of the yields of the (γ, n), (n, 2n), and (γ, 2n) reactions on the ¹¹³In nucleus. The energy dependence of the isomeric ratios of the yields of the photonuclear reactions ¹¹³In(γ, n)^112m,g In and ¹¹³In(γ, 2n)^111m,g In is studied in the energy range of 12–35 MeV.     

Level structure of 87Sr from the 86Sr(n, γ) and 86Sr(d,p) reactions

The γ-ray spectrum emitted after thermal neutron capture in ⁸⁶Sr was studied at the ILL high flux reactor with pair- and intrinsic Ge spectrometers. 759 transitions were assigned to the reaction ⁸⁶Sr(n, γ)⁸⁷Sr and 385 of them were placed into a ⁸⁷Sr level scheme of 80 levels. This represents 90% of the observed intensity. The level energies were determined with a precision of better than 20 ppm; the neutron binding energy was determined to be 8428.16 (17)keV. In a second set of experiments high resolution particle spectra of the reactions ⁸⁶Sr(d, p)⁸⁷Sr and ⁸⁸Sr(d, t)⁸⁷Si were recorded at 20 MeV deuteron energy with the München Q3D spectrometer. These data were used to establish newly found levels and to differentiate between primary and secondary transitions in the (n, γ) data. The observed level densities and primary transition strengths are compared with statistical models.     

Comparison of level density models in (γ, n) reactions of some lanthanide nuclei

Level densities are required at excitation energies where discrete level information is not available or incomplete to get a reliable theoretical analysis of cross sections, spectra, and angular distributions. The total reaction cross sections of some lanthanides (¹⁴¹Pr, ¹⁴²Nd, ¹⁴⁴Sm, ¹⁵³Eu, ¹⁶⁰Gd, ¹⁵⁹Tb, ¹⁶⁵Ho, ¹⁷⁵Lu) were calculated using TALYS 1.2 code for gamma-induced reactions through the five level density models in the incident gamma energy range from 5 to 30 MeV. All calculations from the present study were compared with each other and with the experimental data obtained from EXFOR library. The total photo-neutron reaction cross-section values obtained from the model calculations and experimental measurements taken from EXFOR confirm the presence of systematical disagreements reported in the literature, except ¹⁶⁵Ho case where one can see a satisfactory agreement.     

New data on (γ, n), (γ, 2n), and (γ, 3n) partial photoneutron reactions

Systematic discrepancies between the results of various experiments devoted to determining cross sections for total and partial photoneutron reactions are analyzed by using objective criteria of reliability of data in terms of the transitional photoneutron-multiplicity function F _i = σ(γ, in)/σ(γ, xn), whose values for i = 1, 2, 3, ... cannot exceed by definition 1.00, 0.50, 0.33, ..., respectively. It was found that the majority of experimental data on the cross sections obtained for (γ, n), (γ, 2n), and (γ, 3n) reactions with the aid of methods of photoneutron multiplicity sorting do not meet objective criteria (in particular, F ₂ > 0.50 for a vast body of data). New data on the cross sections for partial reactions on ¹⁸¹Ta and ²⁰⁸Pb nuclei were obtained within a new experimental-theoretical method that was proposed for the evaluation of cross sections for partial reactions and in which the experimental neutron yield cross section σ ^expt(γ, xn) = σ(γ, n) + 2σ(γ, 2n) + 3σ(γ, 3n) + ..., which is free from problems associated with determining neutron multiplicities, is used simultaneously with the functions F _i ^theor calculated within a combined model of photonuclear reactions.     

The influence of the spin-orbital bond on direct photonuclear reactions (γ, n) and (γ, p)

The Courant model for direct photonuclear reactions is modified by using the wave functions of a shell model with spin-orbital bond. It is shown that the introduction of spin-orbital interaction does not influence the cross-section. The changes caused by the spin-orbital bond are apparent only on the angular distribution, which has the Courant forma+bsin² , but with a different value ofb/a, i.e. the anisotropy coefficient. New selection lawsj j, j j±1 are found. The introduction of spin-orbital interaction permits the negative value of the anisotropy coefficient, found in some experimental papers, to be explained in a natural way.

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- - (, n) (, )

: - . , . , - , , a+bsin² , , b/a, . . . j j, j j±1. - , .

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Excerpt from diploma work done at Faculty of Technical and Nuclear Physics in Prague.

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In conclusion the author thanks lecturer J. Kvasnica for the choice of subject and valuable remarks.     

Level structure of 110in from the 110cd(p,nγ)110in reaction

γ-ray and γγ-coincidence spectra of the ¹¹⁰Cd(p, nγ)¹¹⁰In reaction were measured with Ge(Li), Ge(LEPS), and Ge(HP) spectrometers at 6 MeV bombarding proton energy. Energies (E_γ) and relative intensities (I_γ) of 95 ¹¹⁰In transitions (including 70 new ones) have been determined. The electron spectrum of the reaction was measured with a combined magnetic plus Si(Li) spectrometer at E_p = 6 MeV. Internal conversion coefficients of 41 transitions in ¹¹⁰In have been determined for the first time. The angular distribution of γ-rays was measured at 5.2, 5.6, and 6 MeV bombarding proton energies. A new, more complete level scheme of ¹¹⁰In has been deduced. On the basis of the internal conversion coefficients of transitions, Hauser-Feshbach analysis of (p, n) reaction cross sections, γ-ray angular distribution (and other) results unambiguous spin and parity assignments were made to 11 excited ¹¹⁰In levels. The energies of several ¹¹⁰In proton-neutron multiplets were calculated on the basis of the parabolic rule derived from the cluster-vibration model. The comparison of experimental and theoretical results provided identification of about 20 p-n multiplet states in ¹¹⁰In.     

~(100)Mo(n,2n)~(99)Mo,~(96)Mo(n,p)~(96)Nb和~(92)Mo(n,α)~(89m+g)Zr反应截面测量

本文报告了在E_n=13.40—14.79MeV中子能区用活化法以~(27)Al(n,α)~(24)Na截面为中子注量标准测得的~(100)Mo(n,2n)~(99)Mo,~(96)Mo(n,p)~(96)Nb和~(92)Mo(n,α)~(89m+g)Zr的反应截面,中子能量是用铌锆截面比法测定的。文中将实验测量值与理论计算值进行了比较,还对上述三个反应的截面进行了编评,给出了推荐的激发曲线。     

Excitation functions of 40Ar(p,p′γ)40Ar and 40Ar(p,γ)41K reactions

The excitation functions of ⁴⁰Ar(p,p′γ)⁴⁰Ar and ⁴⁰Ar(p,γ)⁴¹K reactions are measured in the E _p = 1.0–3.0 eV range of accelerated protons. The excitation function in the E _p > 2.6 MeV range of accelerated protons is measured for the first time. The strengths of all (more than 200) measured resonance states are calculated.     

On the mechanism of (HI, α x n) reactions

An expression is obtained for the cross sections of (Heavy Ion,α x n) reactions by considering two possible mechanisms: compound nucleus formation and massive transfer. In the latter, an alpha particle is emitted in the very early stage of the reaction while the remnant of the projectile fuses into the target forming an excited nucleus which deexcites by neutron evaporation. A good agreement with the experimental excitation functions of¹⁵⁴Sm(¹⁶O,α x n) reactions is obtained which supports the massive transfer hypothesis.     

The isomeric ratios in some photonuclear reactions (γ, n), (γ, p), (γ, 2n), and (γ, np) induced by bremsstrahlungs with end-point energies in the Giant Dipole Resonance region

We have determined the isomeric ratios in photonuclear reactions ¹¹⁶Cd(γ, n)^{115m, g} Cd, ¹³⁸Ce(γ, n)^{137m, g} Ce, ¹⁵³Eu(γ, n)^{152m, g} Eu, ⁹⁶Mo(γ, p)^{95m, g} Nb, ¹¹⁸Sn(γ, p)^{117m, g} In, ⁸⁹Y(γ, 2n)^{87m, g} Y, ¹⁰⁶Cd(γ, np)^{104m, g} Ag, and ¹¹²Sn(γ, np)^{110m, g} In induced by bremsstrahlungs with end-point energies in the Giant Dipole Resonance (GDR) region. The targets were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna. Gamma spectra of irradiated samples were measured with a spectroscopic system consisting of 8192-channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) semiconductor detector CANBERRA. The results were discussed and compared with those of other authors. The article is published in the original.     

Complication effects in highly-excited state structure of the (γ, n), (e,e′) and (Μ−, γ) reactions

The complication effects in the highly-excited state structure (impurity of the complex configurations of the 2p2h type) of the (, n), (e, e) and (^–, ) nuclear reactions with the⁴⁰Ca nucleus have been studied in terms of the ph-approximation including the following effects: (a) the presence of states of the two particles — two holes type, (b) rigidity loss by nucleus in excited state.     

Investigation of γ radiation from 178Hf in the respective (n, n′γ) reaction

The spectra and angular distributions of gamma rays were measured in the reaction ¹⁷⁸Hf(n, n???) induced by a beam of fast reactor neutrons. Data onmultipole mixtures in gamma transitions and a lot of new information about gamma transitions of energy 1.5 to 3.0 MeV were obtained. A comparison of these results with information known from the respective (n, ??) reaction made it possible to refine the schemes of deexcitation of ¹⁷⁸Hf levels at energies above 1.5 MeV, to determine more precisely features of these levels, and to introduce new levels and rotation bands at excitation energies of about 2MeV.     

Energy levels in159Ho from159Tb(α, 4nγ)159Ho and159Tb(3He, 3nγ)159Ho reactions

The reactions¹⁵⁹Tb(, 4n)¹⁵⁹Ho and¹⁵⁹Tb(³He, 3n)¹⁵⁹Ho have been used to populate states in¹⁵⁹Ho. Gamma-ray spectra in single and coincidence modes have been studied. Assignments have been made for the bands built on the Nilsson states 7/2^–[523], l/2⁺ [411] and l/2^–[541]. The results are discussed in terms of rotational models.     

Structure,stability and magnetic properties of (NiAl)n(n≤6) clusters

In this paper, density functional theory with generalized gradient approximation (GGA) for the exchange-correlation potential has been used to calculate the energetically global-minimum geometries and electronic states of (NiAl)_n(n≤6) clusters. Full structural optimizations, analysis of energy and frequency calculation are performed. The most stable structures of (NiAl)_n clusters are all three-dimensional structures except NiAl. The average bond lengths of (NiAl)_n clusters are larger than that of Ni_2n, and are smaller than that of Al_2n. The binding energy per atom of Ni_2n and (NiAl)_n has the same change trend, and that are larger than that of Al_2n. Stability analysis shows that Ni₈, (NiAl)₂ and Al₁₀ clusters have higher relative stability than other clusters. Mulliken analysis indicates that charges always transfer from Al atoms to Ni atoms, and the average charges of transfer from Al atoms to Ni atoms have a maximum at (NiAl)₆, implying the strong interaction between Al and Ni atoms in (NiAl)₆. The average atomic magnetic moments of (NiAl)_n are smaller than that of true Ni_2n. The analysis of the static polarizability shows that the electronic structures of (NiAl)_n clusters tend to be compact with the increase of atoms.     

Low-lying states of 109Sn from the 106Cd(α, nγ) reaction

Measurements of γ-ray, γγ-coincidence and internal conversion electron spectra from the ¹⁰⁶Cd(α, nγ)¹⁰⁹Sn reaction were carried out at 15–20 MeV α-particle bombarding energies with Ge(HP) γ-ray and superconducting magnetic lens plus Si(Li) electron spectrometers. The energies, relative intensities, internal conversion coefficients and coincidence relations of the ¹⁰⁹Sn transitions were determined, and a more complete, consistent level scheme has been deduced. Spin and parity values have been determined from the internal conversion coefficients, the bombarding-energy dependence of the side-feeding intensities of the states and the available γ-ray angular distribution data. The level scheme was interpreted in the framework of the quasi-particle shell model.