Theoretical Analysis of Neutron Double-Differential Cross Section of n ＋^19F at 14.2 MeV

A new light nuclear reaction model has been developed and the double-differential measurements of lp shell nuclei have been analyzed successfully. Now, the application of this model is expanded to 19F of the 2s-ld shell nucleus. The double-differential cross section of total outgoing neutron for n ＋^19F reactions at En=14.2 MeV has been calculated and analyzed, which agrees fairly well with the experimental measurements. In this paper, the contributions from different reaction channels to the double-differential cross sections have been analyzed in detail. The calculations indicate that this light nudear reaction model is also able to be used for the 2s-ld shell nucleus so long as the related level scheme couM be provided sufficiently.     

Excited States in ^18Ne Studied via ^17F＋p

The elastic resonance scattering of ^17F＋p is studied in inverse kinematics via a thick-target method. The excitation function for ^17F＋p elastic scattering is obtained within the energy interval of Ec.m ≈ 0.4-1.7 MeV. The experimental excitation function is analyzed with a multilevel R-matrix code MULTI7, and the proton widths are deduced. The α decay from 6.15 MeV 1- state in 18Ne is observed, which is critical to the 14O（α, p）17F reaction as the main breakout route from CNO cycle to rp-process in supernovae and x-ray bursts.     

Cross-Correlation of Excitation Functions for Different Fragments and Different Scattering Angles in ^27Al（^19F,x）y Reactions

Excitation functions have been measured for different projectile-like fragments produced in ^27Al（^19F, x ）y reactions at incident energies from 110. 25 to 118. 75 Me V in 250 ke V steps. Strong cross section fluctuations of the excitation functions are observed. The cross-correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle θcm have been deduced. These coefficients are much larger than the statistical theoretical calculated ones. This indicates that there are strong correlations between different exit channels in the dissipative heavy ion collision of ^27Al（^19F, x）y.     

Astrophysical Rates for ^12N（p,γ）^13O Direct Capture Reaction

The proton capture on the unstable nuclei plays a very important role in nucleonsynthesis. The ^12N（p,γ）^13O reaction rates at the energies of astrophysical interest are estimated with the spectroscopic factor and asymptotic normalization coeffcient methods. The present results show that the ^12N（p,γ）^13Oreaction may play an important role in x-ray bursts.     

Observation of Rotational Bands in Neutron—Rich ^106Mo Nucleus

The rotational bands up to a spin of 16h in the neutron-rich ^106Mo nucleus have been ivestigated by measuring high-fold prompt γ-ray coincidence events following spontaneous fission of ^252Cf with a Gammasphere detector array.The ground-state band,the one-phonon and two-phonon γ-vibrational bands,as well as a quasi-particle hand have been confirmed and expanded.The other four collective rotational bands,three proposed as two-quasi-particle bands and one proposed as a β-vibrational band,have been newly observed.The characteristics of these collective bands and the possible configurations for the quasi-particle bands are discussed.     

Investigation on the deformation of Ne and Mg isotope chains within relativistic mean-field model

Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field （RMF） model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that ^19,29,32Ne and ^20,31Mg maybe have a triaxial deformation and ^25-28Ne and ^27-30Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for ^20Mg is predicted to be very weak.     

Iosotopic Distributions of the ^18N Fragmentation Products in Coincidence with Neutrons on Targets ^197Au and ^9Be

We present the experimental isotopic distributions of the ^18N projectile fragmentation products Li,Be,B and C in coincidence with neutrons,as well as the inclusive ones on ^197Au and ^9Be targets.In the framework of the abrasion-ablation model,these distributions are calculated for various nucleon density distributions of the projectile.The comparison with experimental isotopic distributions of the projectile-like fragments in coincidence with neutrons shows that the information on the nucleon density distribution of the ^18N projectile can be extracted.     

^5He Emission in Neutron-Induced ^10B Reactions

In n ＋^10B reactions, ^5He cluster emission has been discussed with the updated level scheme and the new optical model parameters. In this paper the reaction channels related to ^5He emission are listed in detail. By using the new reaction model for light nuclei, the double-differential cross sections of total outgoing neutrons for n ＋ ^10 B reactions at En= 14.2 MeV have been calculated, and the results agree fairly well with the measurements. Particularly, in the energy-angular spectra the contribution from the 5He-emission to the total outgoing neutron double-differential cross sections has also been analyzed, and the partial energy-angular spectra of 60° at En= 14.2 MeV have been given. The calculated results indicate that once the 5He emission is taken into account, the fitting with the double-differential measurements of total outgoing neutrons at the low energy region could be improved. Therefore, to consider the ^5He emission properly in the reaction processes of light nuclei is necessary.     

High-Resolution Spectra of the ^10B^18O and ^11B^18O： Rotational Analysis of the B-X Bands

Emission spectra of ^10B^18 O and ^11B^18 O isotopomers in the 230-330nm region have been investigated by means of conventional high-resolution spectroscopy. The molecules were produced in a low-pressure arc by discharging 8 Torr of mixture containing argon and oxygen 18 in the ratio of 4:1 and the spectra have been recorded using Ebert-type spectrograph. The boron needed to produce BO has been present in the system as amorphous powder with natural abundance of ^10B and ^11B. Rotational analysis of the 0, 0 and 0, 1 bands has been performed and spectroscopic constants have been extracted. The results have allowed first determination of the equilibrium rotational constants Be and De for both isotope species ^10B^18O and ^11B^18O in their lower electronic state.Assuming a linear dependence of Be on (v 1/2), the value of equilibrium distance re in the lower state has been derived.     

Water Gas Shift Reaction： A Monte Carlo Simulation

The water gas shift （WGS） reaction is reacts with water on a catalytic surface a process of industrial importance to form CO2 and H2. We study this In this reaction carbon monoxide reaction with thermal （Langmuir- Hinshelwood） and non-thermal （precursor and Eley-Rideal） reaction mechanisms using the techniques of Monte Carlo computer simulation. The details of surface coverages and production rates are given as a function of CO partial pressure. The diffusion of species on the surface as well as their desorption from the surface is also introduced to include temperature effects. The phase diagrams of the system have been drawn to observe the behaviour of reacting species on the surface. The study reveals that the production rates are higher for non-thermal precursor mechanism and are in agreement with the experimental finding.     

Neutron Spectroscopic Factors of ^7Li and Astrophysical ^6Li（n,γ）^7Li Reaction Rates

Angular distributions of the ^7Li（^6Li, ^6Li）^7Li elastic scattering and the ^7Li（^6Li, ^7Lig.s.）^6Li, ^7Li（^6Li, ^7Li0.48）^6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of ^6Li ＋ ^7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation （DWBA） analysis, spectroscopic factors of ^7Li =^6Li n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in ^7Li, respectively. Using the spectroscopic factors, the cross sections of the ^6 Li（n, γ0,1）^7 Li direct neutron capture reactions and the astrophysical ^6Li（n, γ）^7 Li reaction rates are derived.     

Theoretical simulations of emission spectra of Fe^7＋ and Fe^＋8

The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code （FAC）. These atomic data are used to analyse the emission spectra of both laboratory and astrophysical plasmas. The nf-3d emission lines have been simulated for Fe VIII and Fe IX in a wavelength range of 6-14 nm. For Fe VIII, the predicted relative intensities of lines are insensitive to temperature. For Fe IX, however, the intensity ratios are very sensitive to temperature, implying that the information of temperature in the experiment can be inferred. Detailed line analyses have also been carried out in a wavelength range of 60-80 nm for Fe VIII, where the solar ultraviolet measurements of emitted radiation spectrometer records a large number of spectra. More lines can be identified with the aid of present atomic data. A complete dataset is available electronically from http：//www.astrnomy.csdb.cn/EIE/.     

Exotic Behaviour of Angular Dispersion of Weakly Bound Nucleus ^17F at Small Angles

The differential cross sections of ^17F and ^17O elastic scattering products on ^208Pb have been measured at the Radioactive Ion Beam Line at Lanzhou （RIBLL）. Two angular dispersion plots of In（ dσ/ dθ ） versus 02 are obtained from the angular distribution of the elastic scattering differential cross sections. The angular dispersion plot exhibits a clear turning point for ^17F in the range of small scattering angles 6°-2° due to its exotic structure, but for ^17O, the turning point is not observed in the same angular range. The experimental results have been compared with previous data of other groups. Systematical analysis on the available data supports the above conclusion that there is an exotic behaviour of the angular dispersion plot of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the turning point of the angular dispersion plot appears at small angle for weakly bound nuclei with halo or skin structure, and can be used as a new probe to investigate the halo and skin phenomena of weakly bound nuclei.     

Thermal Shifts and Electron—Phonon Interactions of ^4T2 and ^4T1 Broad Bands for Ruby

For the first time,by taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d^3 electronic electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d^3 electronic configuration,the values of parameters in expressions of Raman and optical-branch terms of thermal shifts (TS) due to EPI for three levels,^4T2 band and ^4T1 band of ruby have been evaluated;the contributions to TS of ^4T2 and ^4T1 broad bands from thermal expansion have also been calculated;and then,the TS of the peak energies of ^4T2 and ^4T1 broad bands have been calculated.The results are in satisfactory agreement with observed data.The values of single-electron reduced matrix elements representing the strengths of EPI of ^4T2 and ^4T1 bands have respectively been determined.For TS of the peak energies of ^4T2 and ^4T1 bands,it is found that the contribution to TS from the second-order term in EPI Hamiltonian is dominant;TS due to EPI of acoustic branches are over two times as much as those of optical branches,and both of them increase rapidly with temperature;the neighbor-level term is insignificant;the contribution to TS from thermal expansion is specially important,and all the three terms of TS of ^4T2 or ^4T1 band are red shifts.     

Test of Determination of (p,γ) Astrophysical S-Factors Using the Asymptotic Normalization Coefficients from Neutron Transfer Reactions

The asymptotic normalization coefficients （ANCs） for the virtual decay ^17 O→^16 O＋n are derived from the angular distributions of the 16 O（d, p）^17O reaction leading to the ground and first excited states of ^17O, respectively, using the distorted wave Born approximation and the adiabatic wave approximation. The ANCs of ^17F are then extracted according to charge symmetry of mirror nuclei and used to calculate the astrophysical S-factors of ^16 O（p, γ）^17 F leading to the first two states of ^17 F. The present results are in good agreement with those from the direct measurement. This provides a test of this indirect method to determine direct astrophysical S-factors of （P, γ） reaction. In addition, the S-factors at zero energy for the direct captures to the ground and first excited states of ^17 F are presented, without the uncertainty associated with the extrapolation from higher energies in direct measurement.     

Ground-State Properties ,of C, O, and Ne Isotopes in Hartree——Fock-Bogoliubov Calculation with Gogny Interaction

Ground-state properties of C, O, and Ne isotopes are described in the framework of Hartree-Fock-Bogoliubov theory with density-dependent finite-range Gogny interaction D1S. We include all the contributions to the Hartree-Fock and pairing feld arising from Gogny and Coulomb interaction as well as the center of mass correction in the numerical calcu/ations. These ground-state properties of C, O, and Ne isotopes are compared with available experimental results, Hartree-Fock plus BCS, shell model and relativistic Hartree--Bogoliubov calculations. The agreement between experiments and our theoretical results is pretty well. The predicted drip-line is dependent strongly on the model and effective interaction due to their sensitivity to various theoretical details. The calculations predict no evidence for halo structure predicted for C,O, and Ne isotopes in a previous RHB study.     

Range Distribution Parameters and Electronic Stopping Power for ^19F^＋ Ions in SnO2, Indium-Tin Oxide, AgGaSe2 and AgGaS2： Comparison Between Theory and Experiment

Range distributions of fluorine for ^19F^ implantation into SnO2, indium-tin oxide, AgGaS2 and AgGaSe2 aremeasured by using the ^19F(p, αγ)^16O resonant nuclear reactions. The electronic stopping cross sections for ^19F ions in these materials are derived from the measured range distributions. These experimental results are compared with those obtained from the newest version of stopping and range computer code, SRIM2003. Thevalues of projected range predicted by the SRIM2003 agree well with the measured values for AgGaS2 andAgGaSe2 substrates. However, the values given by the SRIM2003 substantially deviate from the experimentalvalues for the oxide materials SnO2 and ITO.     

New Generation of Experiments for the Investigation of Stellar (p, γ) Reaction Rates Using SAMURAI

The future experimental campaign with the SAMURAI setup at RIKEN will explore a wide range of neutron-deficient nuclei with a particular focus on the most critical  (p, γ)  reaction rates relevant to the astrophysical rp-process in type-I X-ray bursts (XRB). Intense radioactive-ion (RI) beams at an energy of a few hundred MeV/nucleon will be deployed to populate proton-unbound states in the nuclei of interest through the Coulomb excitation or nucleon-removal processes. The decay of these states into a proton and a heavy residue will be measured using complete kinematics and the information about timereversal proton-capture process will be obtained. This method will provide the vital experimental data on the resonances, which dominate the stellar (p,γ) reaction rates, as well as on the direct proton-capture process for some other cases. The experimental setup will utilize for the first time the High-Resolution 90?-mode of the SAMURAI spectrometer in combination with the existing detection systems, including custom-designed Si-strip detectors for simultaneous detection and tracking of heavy ions and protons emitted from the target. The details of the experimental method and the utilized apparatus are discussed in this paper.     

Angular Distribution and Angular Dispersion in Collision of ^19F＋^27Al at 114 MeV

Angular distributions of fragments B, C, N, O, F, Ne, Na, Mg and Al induced by the collision of ^19F ^27Al at 114 MeV have been measured. Angular dispersion parameters are extracted from the experimental data and compared with the theoretical ones. The dynamic dispersions for dissipative products depend strongly on the charge number Z of the fragments.     

Low-Energy Direct Capture in the ^12C（α, γ）^16O Reaction

The spectra of light nuclei provide the first test of nuclear interaction models. The reaction amount determines the relative abundance of most elements in red giant stars, neutron stars, and black holes. Due to the fact that this reaction occurs at low energies, the experimental measurement is very difficult and perhaps impossible. In this work, the radiative capture of the ^12C（α, γ）^16O reaction at very low-energies is taken as a case study. Using the M3Y potential we calculate the astrophysical Factor for transition E1 and E2. In comparison with other theoretical methods and available recent experimental data, excellent agreement is achieved for the astrophysical S-factor of this process.