Mn FROM NEUTRON SPECTRA B.V. Zhuravlev, A.A. Lychagin, N.N.Titarenko, V.G. Demenkov, V.I. Trykova

Transcription

1 NUCLAR LVL DNSITIS OF 47 V 48 V 49 V 53 Mn 54 Mn FROM NUTRON SPCTRA B.V. Zhuravev A.A. Lychagin N.N.Titarenko V.G. Demenkov V.I. Trykova State Scientific Center of Russian Federation - Institute for Physics and Power ngineering 4933 Obninsk Kauga Region Russia The experimenta data on the nucear eve densities for many nucei are derived in the main from the anaysis of ow-ying eve and neutron resonance data. However this information is imited to rather narrow ranges of excitation energy and spin and its extrapoation can ead to essentia errors both in absoute vaue of the nucear eve density and its energy dependence especiay in transition fied from we-identified discrete states to continuum part of excitation spectrum. Obviousy it is necessary to attract other experimenta methods of the nucear eve density determination with scope of more wide ranges of excitation energy and spin. Such method has been the study of the spectra of partices emitted in nucear reactions. In this case the type of reaction and the energy of incident partices shoud be chosen so that the contribution of nonequiibrium processes was minimum. These conditions are satisfied with pn reaction at proton energy up to 11 MeV. In the present work the neutron spectra from pn reaction on nucei of 47 Ti 48 Ti 49 Ti 53 Cr 54 Cr in proton energy range of 7-11 MeV have been measured and anayzed in the framework of statistica theory of nucear reactions to study the nucear eve densities of 47 V 48 V 49 V 53 Mn 54 Mn.

2 xperiment

3 σ n mb/mev 1 p=8.8 MeV σ n mb/mev 1 p=8.7 MeV σ n mb/mev p=9.13 MeV Ange-integrated neutron emission spectra from 49 Tipn 49 V reaction. 1-1 σ n mb/mev 1 p=11.17 MeV n MeV

4 Scheme of a compound nuceus reaction for specific exampe.

5 Data anaysis The method of nucear eve density determination from emission spectra is based on the fact that the nucear eve density is one of the most critica component of statistica mode cacuations. The procedure of nucear eve density determination consisted in foowing: The mode parameters of the eve density are adusted such that the crosssection cacuated by means of Hauser-Feshbach formua fits the measured vaue in the energy range of we-known ow-ying eves. It means that the tota decay width of compound nuceus is determined. Using at first the chosen mode of the eve density and in next iterations the absoute vaues of the eve density the differentia cross-section for continuum part of spectrum is cacuated and the absoute eve density is determined in a wide range of excitation energy from the best fit with the spectra measured. cos θ ρ τ θ σ α k n k k k P Q S B S B S K dd d = Ω = c U n c du Q T T T T α ρ τ ; ; KS W K W K S B f i i i S i f k i f = ρ U = ρ Uassumed [dσ /dnmeas. / dσ /dncac.]

6 V Resuts: The extracted eve densities for residua nucei of 47 V 48 V 49 V 53 Mn and 54 Mn excited in reactions studied are presented in the next figs. The tota uncertainties of the eve densities are about 17 %. ρu ρ 1/MeV 1 Nucear eve density of 47 V. 1 1 xperimenta data: o - present work histogram - ow-ying eve data. The curves are cacuated resuts: soid - GSN dashed - BSFG dash-dotted - G-C systematics U MeV

7 V ρu 1/MeV Nucear eve density of 48 V. 1 xperimenta data: o - present work histogram - ow-ying eve data. The curves are cacuated resuts: soid - GSN dashed - BSFG dash-dotted - G-C systematics U MeV

8 V ρu 1/MeV Nucear eve density of 49 V. 1 1 xperimenta data: o present work histogram - ow-ying eve data - proton resonance data. The curves are cacuated resuts: soid - GSN dashed - BSFG dash-dotted - G-C systematics U MeV

9 Mn 1 3 ρu ρ MeV Nucear eve density of 53 Mn. xperimenta data: o - present work histogram - ow-ying eve data - proton resonance data. The curves are cacuated resuts: soid - GSN dashed - BSFG dash-dotted - G-C systematics U MeV

10 54 Mn 1 3 ρ U 1/ MeV Nucear eve density of 54 Mn.. xperimenta data: o - present work histogram - ow-ying eve data. The curves are cacuated resuts: soid - GSN dashed - BSFG dash-dotted - G-C systematics U MeV

11 Nucear eve density parameters Mode G C BSFG Dis. Leves Parameter Nuceus a x T o a I c N L 47 V a b V a b V a b Mn a b Mn a b

12 Nucear eve density parameters Mode Parameter Nuceus GSN ã o δw γ C v ω 47 V a b V а b V a b Mn a b Mn a b а Parameters correspond the best fit of the obtained resuts b Parameters recommended in systematics.

13 Concusions: 1 The neutron emission spectra in pn reaction on nucei of 47 Ti 48 Ti 49 Ti 53 Cr 54 Cr have been measured in proton energy range of 7-11 MeV and anayzed in the framework of statistica mode of nucear reactions. The absoute nucear eve densities of 47 V 48 V 49 V 53 Mn and 54 Mn theirs energy dependences and mode parameters are determined. 3 In transition fied from we-identified discrete states to continuum part of excitation spectrum the structure is observed connected with unhomogeneties of a singe-partice state spectrum. 4 In energy dependences of nucear eve densities are dispayed odd-even differences. 5 It is shown aso that the obtained data differ essentiay from the predictions of the nucear eve density mode systematics.