93Nb(n,2n)92mNb反应截面测量

用活化法以^27Al(n,α)^24Na反应截面为中子注量标准，对14MeV能区中子引起的^93Nb(n,2n)^92mNb反应截面进行了测量。中子能量由硅探测器法测定。     

Cross-section measurement for the ~(93)Nb(n,2n)~(92g)Nb reaction at the neutron energy of 14.6 MeV by the AMS method

The cross-section for the~(93)Nb(n,2n)~(92g)Nb reaction has been measured at the neutron energy of 14.6 Me V using neutron activation and accelerator mass spectrometry(AMS)determination of the long-lived product nuclide~(92g)Nb.The neutron energy was generated from the D+T neutron source at the China Institute of Atomic Energy(CIAE).The neutron flux was monitored by measuring the activity of~(92m)Nb produced in the competing reaction channel of~(93)Nb(n,2n)~(92m)Nb.At the neutron energy of 14.6 MeV,the~(93)Nb(n,2n)~(92g)Nb reaction cross-section of(736±220)mb was obtained for the first time.     

High spin states in95Tc populated in the93Nb(α, 2nγ) reaction

The⁹³Nb(α, 2nγ)⁹⁵Tc reaction has been studied at a bombarding energy of 22.5 MeV using Ge(Li)-detectors. Gamma singles spectra, gamma-gamma coincidences, excitation functions and gamma angular distribution have been obtained. A level scheme has been constructed. Spin and parity assignments up to 29/2⁺ are given.     

(3He, 2n) excitation functions for some light nuclei

Excitation functions have been measured for the reaction ⁹Be(³He, 2n)¹⁰C over the range $\text{E(}{}^3\text{He}\text{) = 10–41}\text{MeV}$ and for the reaction ²⁷Al(³He, 2n)²⁸P over the range $\text{E(}{}^3\text{He}\text{) = 14–41}$ MeV by detecting β-delayed γ-rays. An excitation function has also been measured for the reaction ²⁴Mg(³He, 2n)²⁵Si over the range $\text{E(}{}^3\text{He}\text{) = 21–43}\text{MeV}$ by detecting β-delayed protons.     

Energy levels in 93Mo populated by the 93Nb(p,nγ) reaction

Energy levels of ⁹³Mo have been investigated by means of the ⁹³Nb(p, nγ)⁹³Mo reaction. The excitation functions of the level de-excitation γ-rays were measured with a Ge(Li) detector under proton bombardment in the energy range 3.0 to 5.0 Me V. A detailed γ-ray decay scheme which includes 69 levels and 123 γ-ray lines was constructed from the threshold energies for 64 γ-rays and the γ-ray excitation functions around five isobaric analogue resonances in the ⁹³Nb(p, nγ) reaction. Spin-parity values for 59 levels and favourable values for 8 levels were assigned from the analysis of relative neutron yields via the isobaric analogue resonances of the parent odd-odd nucleus ⁹⁴Nb. The results of the present experiment are compared with shell-model calculations.     

Properties of excited levels in102Rh by the102Ru(p,nγ) reaction

The level scheme of¹⁰²Rh has been investigated by the¹⁰²Ru(p, nγ) reaction in the proton energy range 3.1 MeV≦E _p≦6 MeV. Excitation functions,γ-γ coincidences and pulsed beam measurements have been performed and a level scheme including 33 excited states up toE _x≈650 keV has been constructed. Theγ-branchings of several levels have also been measured. The lifetimes of 5 excited states have been determined with the centroid-shift method:τ _m(105.2 keV)=(1.3±0.3) ns,τ _m(123.7 keV)=(0.6±0.3) ns,τ _m(178.6 keV)=(1.5±0.3) ns,τ _m(208.7 keV)=(0.5±0.3) ns,τ _m(359.6 keV)=(0.8±0.4) ns. Upper limits have been placed for the lifetimes of 20 other levels.     

Energy levels of 92Nb and 94Tc from 92Zr, 94Mo(p,nγ)92Nb, 94Tc

The γ-decays of the energy levels of ⁹²Nb and ⁹⁴Tc were measured following the ⁹²Zr(p, n)⁹²Nb and ⁹⁴Mo(p, n)⁹⁴Tc reactions. For ⁹²Nb the γ-ray thresholds were measured and a detailed excitation function was obtained near the ⁹³Zr ground-state isobaric analog resonance. Also, γ-γ coincidence measurements with two Ge(Li) detectors were made for both ⁹²Nb and ⁹⁴Tc. The coincidence measurements determined ten energy levels in ⁹²Nb and two levels in ⁹⁴Tc. A comparison with particle transfer reactions is used to elucidate the structure of ⁹²Nb levels observed here but not seen in the transfer reactions.     

Study of energy levels of 92Nb observed in the 92Zr(p,n) reaction

The energy levels of ⁹²Nb were observed in the ⁹²Zr(p, n) reaction by use of the neutron time-of-flight technique. Limits on the spins and parities of the ⁹²Nb levels were placed by observing the enhancement in the relative yield of the final states at an isobaric analog resonance and by the measurement of the relative yield off resonance. The measured enhancements and off-resonance yields are compared with values calculated using the statistical compoundnucleus model. Comparison of results from the two methods is used to obtain spin-parity assignments for nine energy levels lying between 976 and 1739 keV in ⁹²Nb.     

The Zr(d,n)Nb and Zr(d,n)Nb reactions

The (d, n) reaction on ⁹⁰Zr and ⁹⁶Zr has been studied at 12 MeV deuteron bombarding energy using the neutron time-of-flight technique with an overall neutron time resolution of 1.9 ns. Angular distributions of neutron groups leading to states in ⁹¹Nb and ⁹⁷Nb were measured in the angular range between 15° and 60°. The measured cross sections were analyzed in the framework of the distorted-wave theory of stripping reactions to deduce l-values and proton spectroscopic factors of states in the residual nuclei. The results are compared with the corresponding data available from (³He, d) studies. The fractionation of the single-particle proton states and their centroid energies are determined.     

The excitation functions of ~(187)Re(n,2n)~(186m,g)Re reactions

A new value for the emission probability of 137.144 keV γ-rays from ~(186g)Re decay is recommended to be(9.47±0.03)/%.Using this value the measured cross sections for ~(187)Re(n,2n)~(186m)Re and ~(187)Re(n,2n)~(186g)Re reactions around 14 MeV are analyzed,and the cross section for ~(187)Re(n,2n)~(186+g)Re reaction at 14.8 MeV is(2213±116)mb.The UNF code was adopted to calculate the cross sections for the ~(187)Re(n,2n)~(186+g)Re reaction below 20 MeV,fitting to the value(2213±116) mb at 14.8 MeV using a set of optimum neutron optical potential parameters which were obtained based on the relevant experimental data of rhenium.The isomeric cross section ratio for the~(187)Re(n,2n)~(186,g)Re reaction was analyzed using the V-H method based on nuclear statistical theory.Combining these calculated results,the excitation functions for the ~(187)Re(n,2n)~(186m)Re and ~(187)Re(n,2n)~(186g)Re reactions were obtained.The obtained results are in good agreement with the available experimental data.     

A study of the93Nb levels populated via the (n,n′ γ) reaction

De-excitation γ-rays from levels in⁹³Nb up to 2203 keV were observed following inelastic neutron scattering at incident energies between 0.6 and 2.575 MeV. The energy level and decay modes of⁹³Nb are deduced. Spin and parity assignments are based on the comparison of the experimental (n, n′) cross sections with calculated cross sections using Hauser-Feshbach theory corrected for level-width fluctuation corrections. The low-lying levels of⁹³Nb have been studied within the framework of the vibration-particle model to account for their energy and spin assignments, as well as the reduced transition probabilities measured in Coulomb excitation experiments.     

Evidence for boson-mode excitations in the16O(α,n) and20Ne(α,n) excitation functions

Excitation functions for¹⁶O(α,n) and²⁰Ne(α,n) have been measured from threshold to 26 and 31 MeV compound excitation energy, respectively. The dominating compound states are interpreted as boson excitation modes of nuclei with α-particle structure.     

Excited states in91Nb populated in the89Y(α, 2nγ) reaction

The reaction⁸⁹Y(α, 2n γ) was used to populate excited states in⁹¹Nb. The de-excitation of these states was studied by in-beam gamma-ray spectroscopy, involving the measurement of excitation functions, angular distributions and life-times. A 17/2^? isomeric state at 2034 keV and withT _1/2=3.8±0.2 μs was observed; it is interpreted as the highest-spin state of the {(g _9/2)² (p _1/2)} proton configuration. The experimental results are compared with other published data and with shell-model calculations.     

Gamma decay of93Mo states from92Mo (d,pγ) and93Tc β-decay

The decay scheme of the fragmented single neutron states of93Mo up to 3.2 MeV excitation energy is obtained from a⁹²Mo(d,pγ)⁹³Mo coincidence experiment. The total γ-spectrum from⁹²Mo+d shows additional strong γ-decays following the β-decay of⁹³Tc produced by the (d, n) reaction. The decay scheme is discussed in the frame of the particle-core coupling model. The important role of 2⁺ core excited components inE2 andM1 transitions between states with different angular momentum of the single particle component is pointed out.     

Non statistical reaction contributions in (α, n) excitation functions

The excitation function²⁴Mg(α, n)²⁷Si has been measured from threshold to 27 MeV excitation energy. A survey is given of the experimental excitation functions¹²C(α, n)¹⁵O,¹⁶O(α, n)¹⁹Ne,²⁰Ne(α, n)²³Mg and²⁴Mg(α, n)²⁷Si and HF calculations have been made for them. The agreement is good within a factor of 2. The deviations of the experimental data from the pure statistical cross sections show common structures which can be interpreted as direct contributions.     

Low-lying excited states of106Ag studied with the103Rh (α,nγ)106Ag and104Pd (α,pnγ)106Ag Reactions

The level scheme of¹⁰⁶Ag has been studied using the¹⁰³Rh(α,nγ)¹⁰⁶Ag and¹⁰⁴Pd(α,pnγ)¹⁰⁶Ag Reactions. The experimental information is taken fromγ-ray coincidence data using Ge(Li)-Ge(Li) and HPGe-planar Ge(Li) configurations andγ-ray angular distributions. With these measurements 126 γ rays have been assigned to¹⁰⁶Ag with 116 deexciting 78 states below 2.26 MeV in excitation. The location of the 8.4-day 6⁺ isomer is established at 89.63±0.09 keV. Many of the low-lying states are interpreted in terms of a slightly deformed rotor model.     

High spin states in 93mo populated in the (p,n) reaction

High spin states in the $\text{ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{(π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}{}^2$) multiplet in ⁹³Mo were investigated with the ⁹³Nb(p, n) ⁹³Mo reaction. A new isomeric state at 2430 keV with a half-life of 3.53±0.18 ns is interpreted as the lower $\text{17}\text{2}{}^{\mathrm{+}}$ member of the multiplet. A number of further states have been identified. The results are compared to previous experiments and shell model calculations.     

Collective excitation of 103Ag following the (12C,p2nγ) reaction

Excited states of ¹⁰³Ag have been investigated in the ⁹⁴Mo(¹²C, p2nγ)¹⁰³Ag reaction and observed up to 6414 keV excitation energy. A perturbed band based on the 27.6 keV $\text{9}\text{2}$⁺ intrinsic state has been strongly populated up to spin $\text{27}\text{2}$⁺. In addition, two negative-parity bands with spins ranging from $\text{19}\text{2}$^? to at least $\text{29}\text{2}$^? were also observed. An interpretation of the experimental results is proposed in the framework of the axial-symmetric rotor-plus-particle model using deformed self-consistent quasi-particle states.     

The excitation function for the 89Y(n, 2n)88Y reaction

Activation cross sections for the ⁸⁹Y(n, 2n)⁸⁸Y reaction at neutron energies between 12.6 and 17.8 MeV have been measured by using the mixed-powder method and γ-ray detection by a Ge(Li) spectrometer. Using the ²⁷Al(n, α)²⁴Na reaction for monitoring the neutron flux, the measured cross-section values for the ⁸⁹Y(n, 2n)⁸⁸Y reaction were found to be 331±32 mb, 603±58 mb, 820±79 mb, 1040±100 mb, 1072±103 mb, 1172±112 mb, 1221±117 mb and 1218±117 mb at the respective incident neutron energies of 12.6±0.1 MeV, 13.3±0.1 MeV, 14.0±0.4 MeV, 14.9±0.3 MeV, 15.1±0.3 MeV, 16.0±0.4 MeV, 16.7±0.5 MeV and 17.8±0.7 MeV. The measured values are compared with the experimental values of others and with the theoretical values obtained from calculations based on the statistical model for the formation of a compound nucleus and its subsequent emission of neutrons.     

The decay of the 11.80 MeV isobaric analog resonance in93Tc to negative parity states in92Mo

The 2,524 keV 5^? state and 2,848 keV3^? state in⁹²Mo were excited by inelastic proton scattering going through the 11.80 MeV isobaric analog resonance in⁹³Tc. Angular distributions of the 3^?→ 2⁺ and 5^?→ 4⁺ γ-rays were measured and analyzed in order to obtain the partial waves of the outgoing protons.