Nuclear in-medium effects on η dynamics in proton–nucleus collisions

The dynamics of the η meson produced in proton-induced nuclear reactions via the decay of N*(1535)has been investigated within the Lanzhou quantum molecular dynamics transport model.The in-medium modifications of the η production in dense nuclear matter are included in the model,in which an attractive η-nucleon potential is implemented.The impact of the η optical potential on the η dynamics is investigated.It is found that the attractive potential leads to the reduction in high-momentum(kinetic energy) production from the spectra of momentum distributions and inclusive cross sections and increasing the reabsorption process by surrounding nucleons.

Emission of Protons in Inelastic Nucleus-Nucleus Collisions at High Energy

Based on the participant-spectator model and the analysis of particle producing proce-ss, the rapidity distribution and the noninvariant center-of-mass energy spectrum of final pro-tons produced in inelastic nucleus-nucleus collisions are studied.

Nonradiative charge transfer in collisions of protons with rubidium atoms

The nonradiative charge-transfer cross sections for protons colliding with Rb（5s） atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10-a keV-10 keV. The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region. The importance of rotational coupling for chargetransfer process is stressed. Compared with the radiative charge-transfer process, nonradiative charge transfer is a dominant mechanism at energies above 15 eV. The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail. The radiative and nonradiative1 charge-transfer rate coefficients from low to high temperature are presented.

Signs of Phase Transition in High Energy Proton-Proton Collisions

The present work aims to study the possible states of matter and the location of phase boundaries between hadronic gas and the quark-gluon plasma QGP. The boundary at the hadron freeze-out is also considered. Proton-proton collisions at a wide range of center of mass energies are used to examine the phase transition (entropy-temperature) diagram. Local thermodynamic equilibrium is assumed at different intervals of rapidity space. The entropy of the system is expressed in terms of the multiplicity of hadron production in each interval. However, the local temperature is estimated using the average transverse momentum. The values of the critical temperatures are found at the boundaries of the phases with a quite clear description of the states.

Beta-delayed Proton Decay of Proton Drip-line Nucleus ^(142)Ho

Unknown beta-delayed proton precursor^(142)Ho was synthesized in the reaction^(106)Cd(^(40)Ca,p3n)and identified for the first time by using a proton-gamma coincidence measurements in combination with a helium-jet fast tape transport system^([1～3]).Its beta-delayed proton spectrum was observed.The hal-life of^(142)Ho

Single source emission of proton projectile fragments in nucleus-emulsion interactions

The projected angular distribution and transverse momentum distribution of proton projectile fragments produced in 3.7A GeV 160, 500A MeV 56Fe, and 1.7A GeV S4Kr induced by different kinds of emulsion target （H, CNO, and AgBr） interactions are investigated. It is found that the projected angular distribution and transverse momentum distribution can be well represented by a single Gaussian distribution. Comparison of transverse momentum distribution with the Maxwell-Boltzmann distribution reveals that proton projectile fragments are emitted from a single-temperature emission source. The temperature is different for different colliding systems, and linearly depends on the target size.

Theoretical investigations of collision dynamics of cytosine by low-energy (150-1000 eV) proton impact

Using a real-space real-time implementation of time-dependent density functional theory coupled to molecular dynamics(TDDFT-MD)nonadiabatically,we theoretically study both static properties and collision process of cytosine by 150-1000 eV proton impact in the microscopic way.The calculated ground state of cytosine accords well with experiments.It is found that proton is scattered in any case in the present study.The bond break of cytosine occurs when the energy loss of proton is larger than 22 eV and the main dissociation pathway of cytosine is the breaks of C1N2 and N8H10.In the range of 150 eV≤Ek≤360 eV,when the incident energy of proton increases,the excitation becomes more violent even though the interaction time is shortened.While in the range of 360 eV<Ek≤q 1000 eV,the excitation becomes less violent as the incident energy of proton increases,indicating that the interaction time dominates mainly.We also show two typical collision reaction channels by analyzing the molecular ionization,the electronic density evolution,the energy loss of proton,the vibration frequency and the scattering pattern detailedly.The result shows that the loss of electrons can decrease the bond lengths of C3N8 and C5N6 while increase the bond lengths of C4H11,C5H12 and C4C5 after the collision.Furthermore,it is found that the peak of the scattering angle shows a little redshift when compared to that of the loss of kinetic energy of proton.

Isospin Dependence of Fragmentation Cross Sections in Collisions of Neutron-Rich Ca Isotopes with ^(12)C

The cross sections of fragments （δf） produced in the even 36～52Ca projectile frag- mentation reactions at 80 AMeV are calculated in the framework of the statistical abrasion- ablation model. The distributions of af are investigated. Linear correlations between the peak positions of the distributions and charge numbers of the fragment isotopes are found.

Determination of Proton Drip-line Nucleus of P Isotopes

Researches have been made in recent years in the search of the proton drip-line and halo nuclei of P isotopes both in theory^([1～3])and in experimerit~[4].We have deduced the matter,proton,neutron and halo density distribution of^(25)P with the theory of relativistic-mean-field(RMF)by using the parameter set of

Re-visit N／Z Ratio of Free Nucleons from Collisions of Neutron-Rich Nuclei as a Probe of EoS of Asymmetric Nuclear Matter

The N/Z ratio of free nucleons from collisions of neutron-rich nuclei as a function of their momentum is studied by means of isospin-dependent Quantum Molecular Dynamics. We find that this ratio is not only sensitive to the form of the density dependence of the symmetry potential energy but also its strength determined by the symmetry energy coefficient. The uncertainties about the symmetry energy coefficient influence the accuracy of probing the density dependence of the symmetry energy by means of the N/Z ratio of free nucleons of neutron-rich nuclei.

Isospin Influence of Colliding System on Nucleon Emissions in Intermediate Energy Heavy Ion Collisions

Fig.1 shows the impact parameter-averaged asymptotic values of N_n and N_p i.e.b(left window)and b(right window)as a function of the neutron-proton ratio of the colliding system with the same target mass and the same projectile mass for six colliding systems:^(74)Kr+^(74)Se,^(74)Se+^(74)Se,^(74)Ge+^(74)Se,^(74)Ge+^(74)Ge,

A theoretical study of fragmentation dynamics of water dimer by proton impact

To investigate the collision processes of proton with the water dimer(H_(2)O)_(2)at 50 e V,the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied.Six specific collision orientations with various impact parameters are considered.The reaction channels,the mass distribution and the fragmentation mass spectrum are explored.Among all launched samples,the probability of the channel of non-charge transfer scattering and charge transfer scattering is about 80%,hinting that the probability of fragmentation is about 20%.The reaction channel of proton exchange process 2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions,the respective distance,the number of loss of electrons and the evolution of the electron density.The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments,the fragment with mass 36 has the highest relative abundance of 65%.The relative abundances of fragments with masses 1,35,and 34are 20%,13%,and 1.5%,respectively.For the total electron capture cross section,the present calculations agree with the available measurements and calculations over the energy range from 50 e V to 12 ke V.

质子入射Al_(x)Ga_(1-x)N材料的位移损伤模拟

氮化镓材料由于优良的电学特性以及耐辐照性能,其与不同含量Al_(x)Ga_(1-x)N材料组成的电子器件,有望应用于未来空间电子系统中.然而目前关于氮化镓位移损伤机理研究多关注于氮化镓材料,对于Al_(x)Ga_(1-x)N材料位移损伤研究较少.本文通过两体碰撞近似理论模拟了10 keV-300 MeV质子在不同Al元素含量的Al_(x)Ga_(1-x)N材料中的位移损伤机理.结果表明质子在Al_(x)Ga_(1-x)N材料中产生的非电离能损随质子能量增大而下降,当质子能量低于40 MeV时,非电离能损随着Al含量的增大而变大,当质子能量升高时该趋势相反;分析由质子导致的初级撞出原子以及非电离能量沉积,发现不同Al_(x)Ga_(1-x)N材料初级撞出原子能谱虽然相似,然而Al元素含量越高,由弹性碰撞产生的自身初级撞出原子比例越高;对于质子在不同深度造成的非电离能量沉积,弹性碰撞导致的能量沉积在径迹末端最大,而非弹性碰撞导致的能量沉积在径迹前端均匀分布,径迹末端减小,并且低能质子主要是通过弹性碰撞造成非电离能量沉积,而高能质子恰好相反.本研究揭示了不同Al元素含量的Al_(x)Ga_(1-x)N材料质子位移损伤机理,为GaN器件在空间辐射环境下的应用提供参考依据.

Gluon saturation and net-proton spectra in relativistic nucleus-nucleus collisions

By means of the AKK08 fragmentation function, the net-proton transverse momentum （pT） spectra in A＋A collisions are studied with two phenomenological models based on the Color Glass Condensate formalism. After a χ2 analysis of the experimental data from BRAHMS, the normalization constant C is extracted at RHIC energies of √sNN =62.4 and 200 GeV, and the theoretical results of the net-proton pT spectra at selected rapidities are also given. It is shown that the theoretical results are in good agreement with the experimental data. Finally, assuming the constant C should have an exponent dependence of √sNN, we also predict the theoretical results of net-proton pT spectra at LHC energies of √sNN = 2.76, 3.94, and 5.52 TeV.

η production in proton-nucleus collisions near threshold

The η-meson production in proton-nucleus （pA） collisions near threshold is studied within a rela- tivistic meson-exchange model. The primary production amplitude is presented in the distorted-wave impulse approximation for the nucleus with isospin 0 or 1 by assuming that N^＊（1535） is excited via a meson exchange and then decays into η and nucleon pair（nN）. Taking ISO and 12C nuclei as examples, we evaluate the prouction cross sections as a function of the incident proton energy, and analyze the effects of nuclear medium and various meson-exchange contributions. Finally we discuss implications for further experimental studies at the Cooling Storage Ring （CSR） in Lanzhou.

Density Distribution of ~8B Deduced with Core Plus Valence Proton

A popular method to fit the experimental data of nuclear total reaction cros section is the Glauber model.It fits the experimental data at high energy very well,but has a big difference at ingermediate energy.We have added the coulomb correction and the finite range correction into the Glauber model and used 2-parameter Fermi density distribution:

Sites of Protonation and Unimolecular Fragmentation of Protonated N-Hydroxyphthalimide in the Gas Phase

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EVIDENCE OF LIQUID-GAS AND CONFINEUNCONFINE PHASE TRANSITION IN RELATIVISTIC NUCLEUS COLLISIONS

In recent years the study of relativistic nucleus-nucleus collisions has been regarded as a front of nuclear physics because the nucleus is an ideal field for strong interaction and in the processes of the collisions there might emerge new forms of nuclear matter, i.e. liquid-gas phase transition (LGPT) and the confine-unconfine phase transition (CUPT) might occur.

Probing the symmetry potential with neutron-proton bremsstrahlung in heavy-ion collisions

In the framework of the isospin-dependent quantum molecular dynamics transport model （QMD）, the effects of symmetry potential on the collision number and the neutron-proton bremsstrahlung photon in the reactions of 40Ca＋40Ca, 124Sn＋124Sn, 40Ca＋64Zn, 40Ca＋124Sn at different incident beam energies are studied. It is found that the collision number shows moderate sensitivity to the stiffness of the symmetry potential and the number of hard photons calculated with stiff symmetry potential is obviously smaller than that with soft symmetry potential. Thus, the neutron-proton bremsstrahlung photons produced in heavy-ion collisions may be a useful probe for the high-density behavior of the nuclear symmetry potential.

3-苯基-1-丁炔-3-醇质谱碎裂中[C_8H_7]^+的结构及分子内质子迁移反应

报道了3-苯基-1-丁炔-3-醇的常规电子轰击质谱(EIMS).利用碰撞诱导解离(CID)技术研究了质谱碎裂过程中产生的[C_8H_7]^+的气相离子结构.同时,氘代同位素交换、亚稳(MI)和CID实验进一步证实了m/z103离子的形成并不是分子离子的质谱碎裂中顺次失去甲基自由基和中性CO分子的直接氢迁移的协同反应,而是在失去CO分子前后发生了二次质子迁移反应的逐步过程.在此基础上提出了一种独特的双分子质子键合复合物中间体的碎裂机理.