Muon transfer from protium to helium isotopes at low temperature

The transfer reaction of negative muons from muonic protium to ³ and ⁴ in binary and triple gas mixtures was studied. In the binary mixtures the transfer rates to the two helium isotopes were determined from the time distribution of the 7-keV X-rays of the intermediate muonic molecule (pμHe)*. The experimental transfer rate to ⁴ is in good agreement with theoretical predictions, whereas the rate to ³ is a factor 2 to 3 smaller than the predicted ones. Radiative branching ratios of the (pμHe)8 molecular decay were obtained. Muon transfer from excited states of muonic protium gives the main contribution to the total intensity of the μHe Lyman series in the binary mixtures. Values of q _1s ^He are determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Muon transfer from protium to helium

Muon transfer from hydrogen isotopes to helium is of importance in muon-catalyzed fusion and serves as a unique tool for the direct observation of the mesomolecular ion (pµHe)^*. During two data-taking runs in 1994 and 1995 at PSI, measurements of the transfer from protium to helium were carried out using CCD's and Ge-diodes as independent X-ray detectors to obtain information on the time distribution and intensity of the 7 keV decay X-ray of the mesomolecular ion. Dual¹H₂ +⁴ He and triple¹H₂ + Ne +^3,4He gas mixtures at low temperatures were investigated to extract transfer rates. Protium of high purity was available. For the first time a transfer rate from muonic protium to³He was measured. A general survey of our measurements and preliminary analysis is presented.     

Cluster transfer reactions at low energies

Acta physica Academiae Scientiarum Hungaricae - The cluster transfer processes below the Coulomb barrier are investigated for arbitrary charges and angular momentum transfer, taking into account...     

Experimental investigation of the muon transfer reaction from deuterium to helium isotopes

Muon transfer from the ground state of muonic deuterium to a helium atom proceeds mainly via the formation of a muonic molecule in an excited state. A large number of decay X rays ( 6.8 keV) from these (dµHe)^* molecules were observed for the⁴He as well as for the³He case. The time distributions of these X rays allow the determination of the ground state transfer rate. The simultaneous employment of Ge/Si-detectors and CCDs for the same target conditions allows the determination of the branching ratio of radiative to nonradiative decay for the first time.     

Emission of heavy clusters in nuclear reactions at low collision energies

A survey of theoretical and experimental investigations of the process involving the emission of heavy clusters from excited nuclear systems produced in heavy-ion reactions at low collision energies is given. The dinuclear system (DNS) model for calculating cross sections for the formation of heavy clusters in complete-fusion and quasifission reactions is described in detail. The results of respective calculations are compared with relevant experimental data and with the results obtained on the basis of different models. The role of the angular momentum, the asymmetry of the entrance channel, the N/Z ratio, and the excitation energy in the formation of final reaction products is studied within the proposed approach. A method is developed for calculating cross sections for evaporation-residue formation. This method takes into account both channels of light-particle emission and channels of heavy-cluster emission. The possibility for the formation of Rn, Fr, and Ra isotopes in channels of heavy-cluster emission from the excited compound nucleus of Pu is demonstrated for the first time. The calculated cross sections and isotopic distributions for residual nuclei arising upon the emission of heavy clusters from an excited compound nucleus of Pu are in good agreement with experimental data. The model developed in the present study permits finding optimum experimental conditions (projectile-target combination and bombarding energy) for studying processes involving the emission of specific complex fragments.     

On the pion-nucleus dynamics at low energies

Low-energy pion scattering (up to 50 MeV) on ¹²C and ¹⁶O is described quantitatively in the framework of the UST approach. It is shown that at T_π ∼ 50 MeV the differential cross sections arise as a result of a strong interference between the pure potential and absorption channels. The importance of nuclear structure effects in the pion-nucleus dynamics at low energies is discussed.     

On photonuclear reaction mechanisms at intermediate energies

The¹²C(γ,2N) reactions have been studied using tagged photons ofE _γ = 114–600 MeV at the Mainz microtron (MAMI). The cross sections of the¹²C(γ,pn) reaction and the shape of¹²C(γ,pp) spectra compare well to model predictions over a wide range of photon energies and missing energies, suggesting that the dominant mechanisms of photonuclear reactions are understood.     

Binary collision model for neon Auger spectra from neon ion bombardment of the aluminum surface

A model is developed to account for the angle-resolved Auger spectra from neon ion bombardment of the aluminum surface recently obtained by Pepper and Aron. The neon is assumed to be excited in a single asymmetric neon-aluminum collision and scattered back into the vacuum where it emits an Auger electron. The velocity of the Auger electron acquires a Doppler shift by virtue of the emission from a moving source. The dependence of the Auger peak shape and energy on the incident ion energy, angle of incidence and on the angle of Auger electron emission with respect to the surface is presented. Satisfactory agreement with the angle resolved experimental observations is obtained. The dependence of the angle-integrated Auger yield on the incident ion energy and angle of incidence is also obtained and shown to be in satisfactory agreement with available experimental evidence.     

中速C3+与Ne原子靶相互作用过程中单电子转移绝对截面的测量

实验测量了2.2‰-4.2v0(v0为玻尔速度,v0=2.19×108cm/s)的C3 与Ne原子碰撞过程中单电子转移绝对截面.将实验结果与多体经典轨道蒙特卡罗模拟计算结果进行了比较.用电离能的变化、屏蔽效应、动态关联对实验和理论计算结果间的数值差异做了分析.总体上,实验结果与多体经典轨道蒙特卡罗方法计算结果在趋势上相符很好.此外,还简单分析了多电子原子的转移多电离机制.     

Measurement of the 11B(11B, 10Be)12C proton transfer reaction at low energies

Differential cross sections for the ¹¹B(¹¹B,¹⁰Be)¹²C proton transfer reaction leading to the ¹⁰Be(g.sO+¹²C(4.43 MeV) $\text{(Q = 0.289}\text{MeV}\text{)}\text{and}{}^{10}\text{(3.37}\text{MeV}\text{) +}{}^{12}\text{C}\text{(g.s.) (Q = 1.36}\text{Me V}\text{)}$ final channels have been measured at E_c.m. = 5.5 MeV by coincident detection of the ¹⁰Be and ¹²C nuclei. The integrated cross sections for the ¹⁰Be + ¹²C(4.43 MeV) channel have been obtained for incident energies between E_c.m. = 2.66 and 3.64 MeV from the yields of the 4.43 MeV γ-ray emitted in the ¹²C 4.43 MeV → g.s. transition. The cross-section magnitudes compare well with the DWBA calculations. The sub-barrier transfer cross sections exhibit an unusual energy dependence: their ratio to the total reaction cross section is decreasing with decreasing incident energy.     

Theoretical study on collision dynamics of H+ + H2O at low energies

Scattering dynamics of a water molecule in collision with proton is studied based on a time-dependent density functional theory and coupled with the molecular dynamics method, in which the electrons are described by quantum mechanics and the nuclei are described by classical mechanics. Four different incident directions at 46 eV are chosen in order to investigate the orientations effect, and the energy-dependent effect in low energy region is explored under impact energies 27, 36 and 46 eV. Reaction channels, scattering angles and energy loss of protons are calculated. The differences between those characteristics are unobvious in large impact parameters, which are irrespective of the incident orientations due to weak projectile-target interaction. In small impact parameters, the results strongly depend on the collision energy and orientation.     

Alpha transfer at sub-coulomb energies in the 9Be + 16O reaction

From a detailed comparison of the sub-Coulomb-barrier cross sections for the ⁹Be + ¹⁶O and ¹²C + ¹³C reactions, it is demonstrated that there is a strong α-transfer in the channel ⁹Be + ¹⁶O→²⁰Ne¹ + ⁵He, in accord with the near optimum Q-value for the α-transfer.     

Muon transfer from hot muonic hydrogen atoms to neon

A negative muon beam has been directed on adjacent solid layers of hydrogen and neon. Three targets differing by their deuterium concentration were investigated. Muonic hydrogen atoms can drift to the neon layer where the muon is immediately transferred. The time structure of the muonic neon X-rays follows the exponential law with a disappearance rate corresponding to the one of ^–p atoms in each target. The rates _pp and _pd can be extracted     

Is the madison convention really convenient at low energies? : The reaction

It is shown that s-wave induced reactions with polarized particles can be described much more conveniently in new coordinates. Even with higher partial waves, cross sections can be fitted with less parameters than in conventional expansions.     

Methods to determine neutrino flux at low energies

We present a set of recommendations for the presentation of LHC results on searches for new physics, which are aimed at providing a more efficient flow of scientific information between the experimental collaborations and the rest of the high energy physics community, and at facilitating the interpretation of the results in a wide class of models. Implementing these recommendations would aid the full exploitation of the physics potential of the LHC.     

Modified Duller-Walker approach to study N-N collision events at cosmic ray energies

High energy nucleon-nucleon collision events are analysed in the light of modified Duller-Walker approach as proposed in a recent paper by Ghosh et al. The result of the analysis clearly justifies the validity of the modified D. W. approach in the cosmic ray energy from 100 to 10,000 GeV.