14MeV中子引起的185Re(n,2n)184g,mRe和191Ir(n,2n)190Ir的核反应截面测量

利用活化方法测量了1?4MeV中子引起的¹⁸⁵Re(n,2n)^184gRe,¹⁸⁵Re(n,2n)^184mRe和¹⁹¹Ir(n,2n)¹⁹⁰Ir核反应的截面.中子能量E_n=(14.7±0.2)MeV时的实验结果分别为:(1817±85)mb,(390±18)mb和(2038±82)mb.并利用HFTT程序计算了中子能量在7—18MeV范围内的截面值,给出了其中两个核反应的激发函数曲线.     

13.5—14.6MeV中子能区镓的同位素反应截面的测量

报道了在13.5—14.6MeV中子能区用活化法以⁹³Nb(n,2n)^92mNb反应截面为中子注量标准测得的⁶⁹Ga(n,2n)⁶⁸Ga,⁶⁹Ga(n,p)^69mZn,⁷¹Ga(n,p)^71mZn和⁷¹Ga(n,n′α)⁶⁷Cu的反应截面值.由(13.5±0.2),(14.1±0.1)和(14.6±0.2)MeV中子引起的⁶⁹Ga(n,2n)68Ga反应截面值分别为(794±31),(869±35)和(986±39)mb,⁷¹Ga(n,n′α)⁶⁷Cu反应截面值分别为(1.3±0.1),(1.7±0.1)和(2.5±0.1)mb.在中子能量为(14.1±0.1)MeV能量点,⁶⁹Ga(n,p)^69mZn反应截面值为(21.5±1.0)mb,⁷¹Ga(n,p)^71mZn反应截面值为(12.4±0.7)mb.单能中子由T(d,n)⁴He反应获得.文中还列举了尽可能收集到的数据以作比较.     

14MeV钕的同位素反应截面的测量

报道了在13.5—14.6MeV中子能区用活化法以⁹³Nb(n,2n)^92mNb反应截面为中子注量标准测得的¹⁵⁰Nd(n,2n)¹⁴⁹Nd,¹⁴⁸Nd(n,2n)¹⁴⁷Nd和¹⁴²Nd(n,2n)¹⁴¹Nd的反应截面值.由13.5±0.2,14.1±0.1和14.6±0.2MeV中子引起的¹⁵⁰Nd(n,2n)¹⁴⁹Nd反应截面值分别为2037±85,1737±68,1657±65mb,¹⁴⁸Nd(n,2n)¹⁴⁷Nd反应截面值分别为1394±58,1416±54,1956±76mb,^{142Nd(n,2n)141Nd反应截面值分别为1501±59,1623±62,1764±111mb.单能中子由T(d,n)4He反应获得.文中还收集了已发表的数据以作比较.}     

63Cu(n,α)60Co反应截面测量

本文报告了E_n=13.6—14.8MeV中子能区用活化法以²⁷Al(n,α)²⁴Na截面为中子注量标准得的⁶³Cu(n,α)⁶⁰Co的反应截面.在中子能量为13.64,13.79,14.03,14.33,14.60和14.80MeV的截面值分别为58.3±3.1,56.3±2.4,53.4±2.0,50.8±1.9,48.4±1.7和47.4±1.7mb.在文中还列举了一些作者的数据以作比较.中子能量是用铌锆截面比法测定的.     

13.5—14.6MeV能区中子引起的50Cr(n,2n)49Cr和52Cr(n,2n)51Cr核反应截面的测量

报告了在13.5-14.6MeV中子能区，用活化法(以93Nb(n，2n)92mNb反应截面为中子注量标准)测得的50Cr(n, 2n)49Cr和52Cr(n, 2n)51Cr的反应截面. 由能量为13.5±0.3 ,14.1±0.2,14.4±0.3 和14.6±0.3MeV的中子引起的50Cr(n, 2n)49Cr反应截面值分别为3.4±0.2,6.8±0.3,21.5±1.0 和25.0±1.2mb，52Cr(n, 2n)51Cr的反应截面值分别为185±10,193±9,258±13 和332±16mb. 单能中子用T(d,n)4He反应获得，其能量用铌锆截面比法测定. 另外，为避免热中子引发的50Cr(n, 2g)51Cr对52Cr(n, 2n)51Cr反应截面的影响，在样品被辐照过程中对样品进行了包镉处理，并将实验结果与尽可能收集到的其它实验数据进行了比较.     

59Co(n,p)59Fe,59Co(n,α)56Mn,59Co(n,2n)58Co反应截面的测量

本实验用活化法测量了中子能量在12.8MeV到17.8MeV的⁵⁹Co(n,p)⁵⁹Fe,⁵⁹Co(n,α)⁵⁶Mn,⁵⁹Co(n,2n)⁵⁸Co三个反应道的反应截面值,实验的测量误差在3.3%—6.9%范围内.     

62Ni(n,α)59Fe反应截面测量

本文报告了在E_n=13.6—14.8MeV中子能区用活化法以²⁷Al(n,α)²⁴Na截面为中子注量标准测得的⁶²Ni(n,α)⁵⁹Fe的反应截面.在E_n为 13.64,13.79,14.00,14.05,14.33,14.60和14.80MeV处的截面分别为17.4±1.1,19.5±1.5,21.9±1.9,22.4±1.6,25.4±1.4,26.1±1.1和26.0±1.1mb.在文章中还列举了所能收集到的一些作者的数据以作比较.中子能量是用铌锆截面比法测定的.     

60Ni(n,p)60Co反应截面测量

本文报告了E_n=13.6—14.8MeV中子能区用活化法以²⁷Al(n,α)²⁴Na截面为中子注量标准得的⁶⁰Ni(n,p)⁶⁰Co的反应截面.在E_n为 13.64,13.79,14.03,14.33,14.60,14.80MeV处的截面分别为184.4±12.2,178.8±10.5,171.4±10.3,161.9±9.6,157.0±9.3,147.5±8.9mb.在文章中还列举了所能收集的一些作者的数据以作比较.中子能量是用铌锆截面比法则定的.     

产生长寿命核的几个(n,2n)反应截面的测量

本文报道了E_n=13.5—14.8MeV中子能区几个长寿命生成核的(n,2n)反应截面的测量.测量方法是以⁹³Nb(n,2n)^92mNb反应截面为中子注量标准的相对活化法.测量的几个反应为:¹⁵¹Eu(n,2n)^150mEu、¹⁵³Eu(n,2n)¹⁵²Eu、¹⁵⁹Tb(n,2n)¹⁵⁸Tb和¹⁰⁹Ag(n,2n)^108mAg.中子能量是用铌锆截面比法测定的.本文的结果和已收集到的测量结果进行了比较.     

107Ag(n,2n)106mAg反应截面测量

本文报告了E_n=13.50—14.73MeV中子能区用活化法以²⁷Al(n,2)²⁴Na截面为中子注量标准得的¹⁰⁷Ag(n,2n)^106mAg的反应截面.在E_n=13.50,13.60,13.90,14.10,14.35,和14.73MeV处的截面分别为469±22,480±22,503±24,538±25,555±25和572±26mb.在文中还列举了一些国外已发表的截面数据以作比较.中子能量用铌锆活度比法测定.     

Levels in Gd158 from the (d,p) reaction

The nuclear spectroscopy of Gd¹⁵⁸ has been investigated by deuteron stripping with magnetic analysis of the resulting protons. Over fifty levels have been observed. Comparison is made of observed and theoretical relative cross sections. Two new rotational bands have been observed; one band based on the 2+ two-quasiparticle state [521 +] – [521?] at 2333.6 keV and a second band based on the 1 + two-quasiparticle state [521 +] – [521?] at 2494 keV. The ground state (d,p)Q-value was found to beQ _o=5706± 5 keV.     

Band mixing in156Gd and158Gd

A detailed investigation of the energies and intensities of the γ-rays that depopulate the low spin levels of the β- and γ-vibrational bands of¹⁵⁶Gd and the γ-vibrational band of¹⁵⁸Gd has been conducted. Both singles and γ-γ coincidence measurements were made on sources of 15-d¹⁵⁶Eu and 46-min¹⁵⁸Eu by use of large volume, high resolution Ge(Li) detectors. In addition to the γ-band at 1154.09 keV, twoK ^π=0⁺ bands were observed in¹⁵⁶Gd with band heads at 1049.45 and 1168.11 keV, respectively. The 2⁺ and 3⁺ members of the γ-vibrational band in¹⁵⁸Gd were observed at 1187.12 and 1265.43 keV, respectively, as well as a newK ^π=0⁺ band at 1195.98 keV. A first order perturbational treatment of the branching ratios was applied to both nuclei. In addition, the mixing between the ground state, the β-, and the γ-vibrational bands of¹⁵⁶Gd is considered from two approaches, but neither satisfactorily explains all the experimentalB(E2) ratios.     

Side feeding times to yrast states of158Dy in26Mg(136Xe, 4n)158Dy

Side feeding times to the yrast states of¹⁵⁸Dy were analyzed and compared with Monte Carlo calculations. It is found that B (E2) value's in pre-yrast stretched E2 transitions are about 80% of the rigid rotor prediction. Average multiplicities and corresponding transition energies are also calculated and compared with the experimental data.     

Gyromagnetic ratios of 4+ and 6+ states in156Gd and158Gd

The followingg-factors have been derived from time integral measurements of γ-γ angular correlations in the static magnetic hyperfine field of magnetized gadolinium metal probes:¹⁵⁶Gd:g(4 ₁ ⁺ )=+0.310(19)g(6 ₁ ⁺ )=+0.25(21)g(4 ₃ ⁺ , 1511 keV)=+0.809(27)¹⁵⁸Gd:g(4 ₁ ⁺ )=+0.409(15). The 5.35d ¹⁵⁶Tb sources were produced by the reaction¹⁵⁶Gd(d, 2n)¹⁵⁶Tb in our cyclotron. A carrier-free 150y ¹⁵⁸Tb source was obtained from ISOLDE/CERN. In comparison with the precisely knowng-factors of the 2 ₁ ⁺ states,g(2 ₁ ^su+ ,¹⁵⁶Gd) =+0.386(4) andg(2 ₁ ⁺ ,¹⁵⁸Gd)=0.381(4), we observe a large reduction for the¹⁵⁶Gd 4 ₁ ⁺ state whereasg increases slightly for¹⁵⁸Gd. The half-life of the 4 ₁ ⁺ state of¹⁵⁸Gd was remeasured as¹⁵⁸Gd:T _1/2(4 ₁ ⁺ )=148(2) ps. A measurement of the rotation in the 4 ₃ ⁺ state of¹⁵⁶Gd in external magnetic fields of various strengths up toB _ext=9.5 T did not confirm the anomalous dependence of the magnetic hyperfine field in gadolinium metal on the external field, which has been reported by Persson et al. [29].     

g-factor of the first excited 4+ states in156Gd and158Gd

Relative g-factor of the first 2⁺ and 4⁺ states have been measured with the transient field technique in¹⁵⁶Gd and¹⁵⁸Gd. The precession of gamma rays depopulating the levels under study were observed, after passing through thin polarized gadolinium. The observed values agree with the predictions of the rotational model, i.c. g(4⁺)= g(2⁺), while contrasting the hypothesis that in¹⁵⁶Gd the g-factor of the 4⁺ is reduced with respect to the 2⁺, because of rotational alignment.     

The level structure of the 153Gd nucleus studied in the 150Sm(α, n)153Gd reaction

The level structure of ¹⁵³Gd has been studied by means of the ¹⁵⁰Sm(α, n)¹⁵³Gd reaction. The experiment included measurements of γ-γ coincidences, γ-angular distributions, γ-ray yield at 17 MeV and 19 MeV beam energy, and γ-ray multiplicities. Favoured and unfavoured members of the positive-parity i_13,2, band were identified. States belonging to the h_9,2 and f_7,2 band structures have been located.Surprisingly low multiplicity numbers were deduced for ₁₅₃Gd γ-rays. This may indicate that the (α, n) reaction is not a pure compound reaction. The level structure of ¹⁵³Gd has been compared to the known structure of other odd-mass N = 89 nuclei, and a close similarity is found.The positive-parity band structure has been compared to calculations with the pairing-plus-recoil model. Good agreement is obtained without any ad hoc Coriolis attenuation.     

Gamma-ray spectra and positive parity bands in 158Gd

A Ge(Li)-NaI(Tl) pair spectrometer and a Ge(Li)-NaI(Tl) anti-Compton spectrometer were used to measure γ-rays from the reaction ¹⁵⁷Gd(n, γ)¹⁵⁸Gd. A detailed decay scheme for levels of ¹⁵⁸Gd was constructed up to an excitation energy of 2504 keV. Branching ratios for transitions from members of the positive parity bands to members of the ground state band were determined. It is shown that a single band-mixing parameter is not sufficient to explain the experimental results, and that even a four-band-mixing calculation does not provide satisfactory agreement. The binding energy of the last neutron is determined to be 7937.4±0.7 keV.     

Excited states in145Gd from the (3He, 2n) reaction

Medium and high spin states in¹⁴⁵Gd up to 3.5 MeV excitation energy have been studied by in-beam gamma ray and conversion electron spectroscopy bombarding enriched¹⁴⁴Sm target with a³He beam. For a part of the identified levels a configuration is proposed in terms of weak coupling of one neutron hole with the¹⁴⁶Gd core or of one neutron particle with the¹⁴⁴Gd core.     

Gyromagnetic ratios of low-lying rotational states in156, 158, 160Gd

Transient-field precessions were measured simultaneously for levels in the ground-state bands of^{156, 158, 160}Gd as ions of these nuclei traversed a thin polarized Fe foil. Relative g-factors of levels up to 6 ₁ ⁺ were deduced, those of the 4 ₁ ⁺ levels being determined with greatest precision. In contrast with the conclusions of the recent report by Alzner et al. [1], our results are consistent with g(4 ₁ ⁺ ) having the same value in all three isotopes and imply g(2 ₁ ⁺ )=g(4 ₁ ⁺ ) in¹⁵⁶Gd, consistent with nuclear structure models.     

Mössbauereffektmessungen am 79,5 keV-Niveau von Gd158

Mössbauer effect measurements with the 79,5 keVγ-transition in Gd¹⁵⁸, populated by thermal neutron capture in Gd¹⁵⁷ are reported. In Gd metal, GdF₃ and GdCl₃, the values obtained for the electric field gradient are (?0.7±0.4), (11.9±5.0) and (?7.5±0.5) · 10¹⁷ V/cm² respectively. The internal magnetic field in Gd metal was measured to beH _int=312±23 kG and we derived for theg factor of the 2 + level the valueg _R=0.385±0.022. The change of the mean square nuclear radius between the ground state and the first excited stateΔ 〈r²〉=+(0.4±0.3) · 10^?3 fm², as extracted from the measurements, will be compared with model calculations of nuclear rotation.