Середні резонансні параметри ядер Ni і Zn

Отримано повнi набори середнiх резонансних параметрiв S0, S1, R'0, R'1, S1,3/2 для ядер нiкелю i цинку з природним складом iзотопiв. Їх визначено з аналiзу середнiх експериментальних диференцiальних перерiзiв пружного розсiяння нейтронiв низьких енергiй розробленим авторами методом. Провед...

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Hauptverfasser: Правдивий, М.М., Корж, І.О., Скляр, М.Т.
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Digital Library of Periodicals of National Academy of Sciences of Ukraine
id nasplib_isofts_kiev_ua-123456789-13378
record_format dspace
spelling Правдивий, М.М.
Корж, І.О.
Скляр, М.Т.
2010-11-05T13:28:11Z
2010-11-05T13:28:11Z
2010
Середні резонансні параметри ядер Ni і Zn / М.М. Правдивий, І.О. Корж, М.Т. Скляр // Укр. фіз. журн. — 2010. — Т. 55, № 2. — С. 170-174. — Бібліогр.: 11 назв. — укр.
2071-0194
PACS 21.60.Ev
https://nasplib.isofts.kiev.ua/handle/123456789/13378
539.171.4
Отримано повнi набори середнiх резонансних параметрiв S0, S1, R'0, R'1, S1,3/2 для ядер нiкелю i цинку з природним складом iзотопiв. Їх визначено з аналiзу середнiх експериментальних диференцiальних перерiзiв пружного розсiяння нейтронiв низьких енергiй розробленим авторами методом. Проведено аналiз отриманих результатiв, рекомендованих параметрiв та деяких лiтературних даних, на основi якого зроблено висновок, що рекомендованi для обох ядер параметри S1 є заниженими у два рази.
Получены полные наборы средних резонансных параметров S1, R'0, R'1, S1,3/2 для ядер никеля и цинка с естественным составом изотопов. Они определены из анализа средних экспериментальных дифференциальных сечений упругого рассеяния нейтронов низких энергий разработанным авторами методом. Проведен анализ полученных результатов, рекомендованных параметров и некоторых литературных данных, в результате которого сделан вывод, что рекомендованные для обоих ядер параметры S1 занижены в два раза.
The complete sets of average resonance parameters S1, R'0, R'1, and S1,3/2 for nickel and zinc nuclei with a natural isotope composition have been obtained. They were determined by analyzing the average experimental differential cross-sections of low-energy neutron elastic scattering with the help of a method developed by the authors. The analysis of obtained results, recommended parameters, and some literary data has been carried out. The conclusion has been made that the recommended values of the parameter S1 are underestimated by a factor of two for both nuclei concerned.
uk
Відділення фізики і астрономії НАН України
Ядра та ядерні реакції
Середні резонансні параметри ядер Ni і Zn
Средние резонансные параметры ядер Ni и Zn
Average Resonance Parameters of Ni and Zn Nuclei
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title Середні резонансні параметри ядер Ni і Zn
spellingShingle Середні резонансні параметри ядер Ni і Zn
Правдивий, М.М.
Корж, І.О.
Скляр, М.Т.
Ядра та ядерні реакції
title_short Середні резонансні параметри ядер Ni і Zn
title_full Середні резонансні параметри ядер Ni і Zn
title_fullStr Середні резонансні параметри ядер Ni і Zn
title_full_unstemmed Середні резонансні параметри ядер Ni і Zn
title_sort середні резонансні параметри ядер ni і zn
author Правдивий, М.М.
Корж, І.О.
Скляр, М.Т.
author_facet Правдивий, М.М.
Корж, І.О.
Скляр, М.Т.
topic Ядра та ядерні реакції
topic_facet Ядра та ядерні реакції
publishDate 2010
language Ukrainian
publisher Відділення фізики і астрономії НАН України
format Article
title_alt Средние резонансные параметры ядер Ni и Zn
Average Resonance Parameters of Ni and Zn Nuclei
description Отримано повнi набори середнiх резонансних параметрiв S0, S1, R'0, R'1, S1,3/2 для ядер нiкелю i цинку з природним складом iзотопiв. Їх визначено з аналiзу середнiх експериментальних диференцiальних перерiзiв пружного розсiяння нейтронiв низьких енергiй розробленим авторами методом. Проведено аналiз отриманих результатiв, рекомендованих параметрiв та деяких лiтературних даних, на основi якого зроблено висновок, що рекомендованi для обох ядер параметри S1 є заниженими у два рази. Получены полные наборы средних резонансных параметров S1, R'0, R'1, S1,3/2 для ядер никеля и цинка с естественным составом изотопов. Они определены из анализа средних экспериментальных дифференциальных сечений упругого рассеяния нейтронов низких энергий разработанным авторами методом. Проведен анализ полученных результатов, рекомендованных параметров и некоторых литературных данных, в результате которого сделан вывод, что рекомендованные для обоих ядер параметры S1 занижены в два раза. The complete sets of average resonance parameters S1, R'0, R'1, and S1,3/2 for nickel and zinc nuclei with a natural isotope composition have been obtained. They were determined by analyzing the average experimental differential cross-sections of low-energy neutron elastic scattering with the help of a method developed by the authors. The analysis of obtained results, recommended parameters, and some literary data has been carried out. The conclusion has been made that the recommended values of the parameter S1 are underestimated by a factor of two for both nuclei concerned.
issn 2071-0194
url https://nasplib.isofts.kiev.ua/handle/123456789/13378
citation_txt Середні резонансні параметри ядер Ni і Zn / М.М. Правдивий, І.О. Корж, М.Т. Скляр // Укр. фіз. журн. — 2010. — Т. 55, № 2. — С. 170-174. — Бібліогр.: 11 назв. — укр.
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AT koržío serednírezonansníparametriâderniízn
AT sklârmt serednírezonansníparametriâderniízn
AT pravdiviimm srednierezonansnyeparametryâderniizn
AT koržío srednierezonansnyeparametryâderniizn
AT sklârmt srednierezonansnyeparametryâderniizn
AT pravdiviimm averageresonanceparametersofniandznnuclei
AT koržío averageresonanceparametersofniandznnuclei
AT sklârmt averageresonanceparametersofniandznnuclei
first_indexed 2025-11-26T03:09:12Z
last_indexed 2025-11-26T03:09:12Z
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fulltext M.M. PRAVDIVY, I.O. KORZH, M.T. SKLYAR AVERAGE RESONANCE PARAMETERS OF Ni AND Zn NUCLEI M.M. PRAVDIVY, I.O. KORZH, M.T. SKLYAR Institute for Nuclear Research, Nat. Acad. of Sci. of Ukraine (47, Nauky Ave., Kyiv 03680, Ukraine; e-mail: sklyar@ kinr. kiev. ua ) PACS 21.60.Ev c©2010 The complete sets of average resonance parameters S0, S1, R′ 0, R′ 1, and S1,3/2 for nickel and zinc nuclei with a natural isotope compo- sition have been obtained. They were determined by analyzing the average experimental differential cross-sections of low-energy neu- tron elastic scattering with the help of a method developed by the authors. The analysis of obtained results, recommended parame- ters, and some literary data has been carried out. The conclusion has been made that the recommended values of the parameter S1 are underestimated by a factor of two for both nuclei concerned. 1. Introduction Within the period of researches of average nuclear res- onance parameters, five editions of the Atlas of recom- mended resonance parameters have already been pub- lished [1]. In comparison with the previous edition [2], there appeared a lot of new experimental data, which al- lowed one to put in order the dependences of parameters S0, S1, and R′0 on the atomic weight A and to consid- erably reduce discrepancies between the parameters of certain nuclei and the results of calculations obtained in the framework of the optical model. However, there remained the unresolved problems concerning the min- ima of parameters S0 (at 100 < A < 140) and S1 (at A ≤ 70). In those ranges, the parameters of neighbor nuclei are 5 to 10 times different, which contradicts the ideology of the optical model and constrains its progress. Isotopes of nickel and zinc are located in that A-range, where the magnitudes of the strength function S1 for many nuclei reveal considerable discrepancies with the results of calculations carried out in the framework of the optical model. For those nuclei, recommended are the parameters S0, S1 and R′0, R′1 we used to calculate the weighted average values for nuclei with natural isotope compositions. Their comparison with the data of work [3] has demonstrated that the values of the parameters S0 and S1 are different by a factor of 2 to 5. In this connection, we tested the agreement of those parameters with experimental data and determined new parameter sets; it was done with the help of a method developed by us for the analysis of the differential cross-sections of elastic low-energy neutron scattering. This method has been successfully used earlier for the determination of resonance parameters of even isotopes of cadmium and tin [4], as well as some other nuclei. 2. Determination Technique for Average Resonance Parameters Neutron scattering by nuclei at energies up to about 450 keV mainly occurs at the orbital moments l = 0 and 1. In this case, the differential cross-sections of elas- tic scattering can be expanded in a series of Legendre polynomials as follows: σel(µ) = σel 4π {1 + ω1P1(µ) + ω2P2(µ)}, (1) where µ = cos θ, θ is the scattering angle, σel is the inte- gral cross-section of elastic scattering, Pl are the Legen- dre polynomials, ω1 and ω2 are the expansion coefficients of the differential cross-sections. These coefficients are referred to as the angular moments of the scattering in- dicatrix, and they are equal to ωl = (2l+ 1)P̄l, where P̄l are the Legendre polynomials averaged over the angles with the weight of a differential scattering cross-section. For even-even nuclei and provided that σt ≈ σel, we obtained the following expressions for the expansion co- efficients [5]: ω1 = 6πλ2 σel (1− η0Re − η1Re + η0Reη1Re + η0Imη1Im), (2) ω2 = 2 σel (σs1 + πλ2T1,3/2), (3) where ηl = ηlRe + iηlIm are the diagonal elements of the average scattering matrix, σs1 are the cross-sections of potential neutron scattering with l = 1, and T1,3/2 are the penetrability coefficients for l = 1 and j = 3/2. In the optical model, the cross-sections σel consist of the corresponding partial cross-sections of compound 170 ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 2 AVERAGE RESONANCE PARAMETERS OF Ni AND Zn NUCLEI and potential neutron scattering, σel = σc0 +σc1 +σs0 + σs1 which are expressed in terms of matrix elements ηl. In the resonance theory, the average cross-sections also consist of the corresponding cross-sections of resonance and potential scatterings which are expressed, in turn, in terms of average resonance parameters. In the case of narrow resonances (Γ� D), the partial cross-sections given by the optical model coincide with the correspond- ing cross-sections obtained in the resonance theory [6]. This allows the matrix elements ηl to be expressed in terms of resonance parameters. Thus, should the quan- tities σel, ω1, and ω2 in Eqs. (1)–(3) be expressed in terms of average resonance parameters, the fitting of those quantities to their experimental values can be used to determine the average resonance parameters S0, S1, R′0, R′1, and S1,3/2 (they are fitting parameters). From the relation S1 = 1/3(S1,1/2 + 2S1,3/2), the parameter S1,1/2 can be found. For carrying out the calculations, we used the cor- responding program for a fitting on the basis of the χ2- minimization method. Three quantities – σel, ω1, and ω2 – were fitted simultaneously, and the χ2-criterion could be monitored for each quantity separately. The tech- nique for the determination of average resonance param- eters is explained in work [5] in detail. 3. Determination of Resonance Parameters and Their Analysis The complete sets of average resonance parameters S0, S1, R′0, R′1, S1,3/2 for nickel and zinc nuclei with the natural composition of isotopes were determined by fit- ting the quantities σel, ω1, and ω2 to the corresponding experimental values taken from work [7] (we carried out the additional averaging of data at the beginning of the energy range). The same data were used to make all the fittings described below and to estimate the quality of their description by means of the resonance parame- ters given by other authors. To check the reliability of the data of work [7] and to make a general evaluation of experimental data in the energy range under investiga- tion, we present our results together with the available experimental data of other authors in the figures given below. For nickel and zinc isotopes, recommended are the pa- rameters S0, S1, and R′0 [1] which were used to calcu- late the weighted average values for nuclei with natural isotope compositions. The obtained values were fixed to determine, by fitting, the other parameters from the complete set. In addition, we calculated the quantities σel, ω1, and ω2 using the parameter sets taken from work Fig. 1. Energy dependences of the quantities σel, ω1, and ω2 for a 28Ni nucleus. Symbols correspond to experimental data, curves are the results of calculations with various sets of resonance parameters (see the text) [3] which were obtained from the same experimental data of work [7], but another method was applied. In every case, the description quality of experimental data was examined by the χ2-value and visually in the plots. 28Ni. In Fig. 1, the experimental energy dependences of the quantities σel, ω1, and ω2 obtained in works [7–10] for nickel nuclei are given. To improve the presentation of the σel-dependence, the first and third points of work [7] were reduced by a factor of two, and the second one by a factor of four. It should be noted that the resonance structures of the total cross-sections only start to reveal themselves in the studied energy range [11], and the res- onances in the cross-sections σel reported in work [7] manifest themselves at energies of about 15 and 65 keV, which testifies to their insufficient averaging. In addi- tion, the authors noted that the cross-sections measured below an energy of about 80 keV are underestimated owing to a substantial resonance self-shielding. The fig- ure demonstrates that there are the appreciable discrep- ancies between experimental data obtained by various authors; they are especially considerable for the quanti- ties ω1 and ω2. The curves in the figure correspond to the results of calculations with the use of different sets of resonance parameters. Curves 2 exhibit the depen- dences for σel, ω1, and ω2 calculated with the following ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 2 171 M.M. PRAVDIVY, I.O. KORZH, M.T. SKLYAR Fig. 2. Energy dependence of the quantities σel, ω1, and ω2 for a nucleus 30Zn set of parameters taken from work [3]: S0 = 1.40(30), S1 = 2.49(52), R′0 = 5.90(49), R′1 = −0.11(50), and S1,3/2 = 1.44(23) (hereafter, the parameters Sl and R′l are given in units of 10−4 and fm, respectively, and the numbers in parentheses indicate the corresponding er- ror). From the figure, one can see that only the experi- mental data for ω1 are described satisfactorily, whereas the other data demonstrate considerable discrepancies. In particular, the calculated cross-sections are less than the experimental ones at the beginning of the energy range, which can be explained by a small value of the parameter S0. The following average values are recommended for nickel parameters: S0 = 3.59, S1 = 0.50, and R′0 = 6.49 [1]. Using the fitting procedure, we determined the other parameters: R′1 = 3.79 and S1,3/2 = 1.52. The de- pendences for the quantities σel, ω1, and ω2 calculated with this set of parameters are presented in the figure by curves 3. It is evident that the description of exper- imental data is satisfactory on the whole, being better than that for the first set. However, from the relation S1 = (S1,1/2 +2S1,3/2)/3, it follows that S1,1/2 = −1.54. According to formula (3), the description of the quan- tity ω2 is mainly determined by the parameters R′1 and S1,3/2. The contribution of the parameter R′1, owing to its smallness, is appreciable only at energies higher than 200 keV. Practically, the parameter S1,3/2 is deter- mined unambiguously from the experimental ω2-values, and the figure testifies that its value is optimal in this case. Therefore, the reason for why the value of the pa- rameter S1,1/2 is unphysical is a small magnitude of the parameter S1. To be convinced of that, we carried out additional calculations. Provided that S1,1/2 = 0 and S1,3/2 = 1.52, the value of S1 cannot be less than 1.01. For S1 = 0.50 and S1,1/2 = 0, we have S1,3/2 = 0.75. When the parameters S0 = 3.59, S1 = 0.50, R′1 = 6.49, and S1,3/2 = 0.75 were fixed, the fitting procedure gave rise to R′1 = 4.03. The calculated values for ω2 are de- picted in the figure by curve 4 (the dependences for σel and ω1 are close to curves 3 ). One can see that they describe neither the data of work [7] nor the data of work [8, 9], the energy dependence of which are abnor- mal and cannot be described at all using resonance pa- rameters. Therefore, there are reasons to consider the recommended value for the parameter S1 as underesti- mated. The insufficient averaging of the data of work [7] and the underestimation of cross-sections at the beginning of the energy range due to the resonance self-shielding result in a mutual disagreement among the quantities σel, ω1, and ω2, which revealed itself in considerable χ2- values at their description, especially in those for the cross-sections. Under such conditions, χ2 is not a reli- able criterion for the quality of a description of experi- mental data, so that the determination of resonance pa- rameters by the automatic fitting and using those data cannot produce the reliable results as well. This is ev- idenced by the results of work [3], in which the values of the parameters S0 and S1 are several times differ- ent from those recommended for this A-region [1], and the description of experimental data is rather doubtful. Therefore, we determined the resonance parameters by stage-by-stage calculations of σel, ω1, and ω2 with se- quential variations of each parameter until the optimal description of experimental data was achieved. The de- scription was estimated both visually (in the plots) and by the χ2-criterion. As a result, the following values were obtained: S0 = 3.80, S1 = 0.95, R′0 = 6.25, R′1 = 3.36, and S1,3/2 = 1.40. The calculated values for σel, ω1, and ω2 are presented by curves 1 in the figure. Accord- ing to the χ2-criterion, our description of experiments was better than that with the parameters of work [3]. Our parameters agree well with their dependences on the atomic weight A, except the parameter S1, the value of which, however, agrees with new data for neighbor nuclei [1, 2]. 30Zn. In Fig. 2, the experimental energy dependences of σel, ω1, and ω2 obtained in works [7, 8, 10] are de- 172 ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 2 AVERAGE RESONANCE PARAMETERS OF Ni AND Zn NUCLEI Average resonance parameters for Ni and Zn nuclei Nucleus S0×104 S1×104 R′ 0, fm R′ 1, fm S1,1/2×104 S1,3/2×104 28Ni 3.80(35) 0.95(26) 6.25(26) 3.36(75) 0.05(1.0) 1.40(32) 30Zn 1.80(25) 0.95(20) 6.50(25) 1.27(90) 0.05(0.9) 1.40(35) picted. To improve the presentation of cross-sections σel in the figure, the second and third points taken from work [7] were reduced by a factor of two. The authors in- dicated that the cross-sections measured below of about 50 keV were underestimated owing to the resonance self- shielding. From the figure, one can see that the appre- ciable discrepancies between the ω1- and ω2-values ob- tained at the end of the energy range in various works are observed. The curves in the figure correspond to the results of calculations with different sets of resonance parameters. Curves 2 in the figure correspond to the results of cal- culations with the parameters taken from work [3]: S0 = 1.15(9), S1 = 1.42(22), R′0 = 6.73(12), R′1 = 0.75(35), and S1,3/2 = 1.23(15). Among all the data, only the quantity ω1 is well described. The other data demon- strate appreciable discrepancies with experiment. For zinc nuclei, the recommended average parameters are S0 = 2.00 and S1 = 0.58. By fitting, the other pa- rameters were determined: R′0 = 6.35, R′1 = 2.11, and S1,3/2 = 1.34. The calculated quantities σel, ω1, and ω2 are presented in the figure by curves 3. One can see that the cross-sections σel at energies above 150 keV are ap- preciably smaller than the experimental ones, whereas the quantities ω1 and ω2 are described satisfactorily. However, as it was for nickel nuclei, there appears an is- sue concerning the value of the parameter S1. From the obtained parameter set, it follows that S1,1/2 = −0.94. If S1 = 0.58 and S1,1/2 = 0, the maximal possible value is S1,3/2 = 0.87. Having fixed the parameters S0 = 2.00, S1 = 0.58, and S1,3/2 = 0.87, we obtained, by fitting, the following other parameters: R′0 = 6.35 and R′1 = 2.18. The description of the quantities σel and ω1 remained practically unchanged. The calculated values of ω2 are shown by curve 4 in the figure. One can see that the description of ω2 became considerably worse, both visu- ally and according to the χ2-value. This means that the value S1,3/2 = 0.87 is too small to provide a satisfac- tory description of ω2-values, so that a conclusion can be drawn that the recommended value of the parameter S1 is underestimated. We determined a new set of resonance parameters in the same way as it was done for nickel nuclei. As a result, the following parameters were obtained: S0 = 1.80, S1 = 0.95, R′0 = 6.50, R′1 = 1.27, and S1,3/2 = 1.40. The results of calculations are shown in the figure by curves 1. One can see that the description of experimental data became appreciably better in comparison with that for the previous sets, both visually and according to the χ2- value. The obtained parameters S0 and R′0 agree well with their dependences on A [1], but the parameter S1, as it was for nickel, is almost twice as large. The results obtained for both nuclei are listed in Table. Hence, the values of the parameter S0 obtained by us for both nuclei confirmed the recommended values, but not those given in work [3]. The values obtained for the parameter S1 confirmed neither the recommended val- ues nor those reported in work [3]. The recommended value of the parameter R′0 for nickel nuclei was con- firmed. From the recommended values of the parameter R′0 for isotopes 64Zn and 66Zn (the latter amounts to 77% of a natural mixture), the weighted average value R′0 = 5.58 was obtained, which is much less that the rec- ommended values for this A-region [1]. By fixing this R′0- value and the recommended values for the parameters S0 and S1, we determined, by fitting, the other parameters: R′1 = 2.41 and S1,3/2 = 1.31. The difficulties associated with the magnitude of the parameter S1 remained in the obtained parameter set; moreover, it does not describe experimental cross-sections at all, because the calculated cross-sections are much less than the experimental ones. The values of R′1 and S1,3/2 taken from three parame- ter sets are mutually agreed, in general, within the error limits. 4. Conclusions In this work, by analyzing the experimental differential cross-sections for low-energy neutron elastic scattering, new complete sets of average resonance parameters S0, S1, R′0, R′1, and S1,3/2 for nickel and zinc nuclei with the natural isotope composition have been determined. In general, the resonance parameters characterize specific nuclei, being determined for nuclear isotopes. However, data for the natural isotope mixture are also very im- portant, in particular, for the specification of parameter dependences on the atomic weight A and for the im- provement of theoretical calculations in the framework of the optical model. As a result of the analysis made, the recommended values for the resonance parameter S1 were found to be underestimated by a factor of about two for both nuclei. At last, it was proved that the available ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 2 173 M.M. PRAVDIVY, I.O. KORZH, M.T. SKLYAR experimental data can be described better without dras- tic and unjustified variations of the parameters S0 and S1, as it was done in work [3]. 1. S.F. Mughabghab, Atlas of Neutron Resonances (Reso- nance Parameters and Thermal Cross Sections. Z = 1– 100), 5th edition (Elsevier, Amsterdam, 2006). 2. S.F. Mughabghab, M. Divadeenam, and N.E. Holden, Neutron Cross Sections (Academic Press, New York, 1981), Vol. 1, Part A. 3. A.B. Popov and G.S. Samosvat, JINR Rapid Commun. N 18-86 (JINR, Dubna, 1986) (in Russian). 4. I.O. Korzh, M.M. Pravdivy, and M.T. Sklyar, in Proceed- ings of the International Conference on Current Problems in Nuclear Physics and Atomic Energy (NPAE–2006), May 29–June 03, Kyiv, Ukraine (Kyiv, 2007), Part 2, p. 599. 5. M.M. Pravdivy, I.O. Korzh, and M.T. Sklyar, Ukr. Fiz. Zh. 49, 627 (2004). 6. A.A. Luk’yanov, Structure of Neutron Cross-Sections (Atomizdat, Moscow, 1978) (in Russian). 7. A.A. Luk’yanov, Zo In Ok, V.G. Nikolenko, A.B. Popov, and G.S. Samosvat, preprint JINR P3-85-133 (JINR, Dubna, 1985). 8. A. Langsdorf, R.O. Lane, and J.E. Monahan, Phys. Rev. 107, 1077 (1957). 9. R.A. Zuhr and K. Min, Nucl. Phys. A 237, 29 (1975). 10. A.B. Smith, in Angular Distributions in Neutron-Induced Reactions, compiled by D.I. Garber et al., 3rd edition (BNL 400, 1970), Vol. 2, p. 28-0-26, 30-0-30. 11. V. McLane, C. Dunford, and P.F. Rose, Neutron Cross Sections (Academic Press, New York, 1988), Vol. 2. Received 24.06.09. Translated from Ukrainian by O.I. Voitenko СЕРЕДНI РЕЗОНАНСНI ПАРАМЕТРИ ЯДЕР Ni I Zn М.М. Правдивий, I.О. Корж, М.Т. Скляр Р е з ю м е Отримано повнi набори середнiх резонансних параметрiв S0, S1, R′ 0, R ′ 1, S1,3/2 для ядер нiкелю i цинку з природним складом iзотопiв. Їх визначено з аналiзу середнiх експеримен- тальних диференцiальних перерiзiв пружного розсiяння ней- тронiв низьких енергiй розробленим авторами методом. Про- ведено аналiз отриманих результатiв, рекомендованих параме- трiв та деяких лiтературних даних, на основi якого зроблено висновок, що рекомендованi для обох ядер параметри S1 є за- ниженими у два рази. 174 ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 2