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The radiation environment on the surface of Mars is a potential threat for future manned exploration missions to this planet. In this study, a simple geometrical model was built for simulating the radiation environment on the Mars surface caused by galactic cosmic rays; the model was built and studied using the Geant4 toolkit. The simulation results were compared with the data reported by a radiation assessment detector (RAD). The simulated spectra of neutrons, photons, protons, $$\alpha$$ α particles, and particle groups $$Z=3$$ Z = 3 –5, $$Z=6$$ Z = 6 –8, $$Z=9$$ Z = 9 –13, and $$Z=14$$ Z = 14 –24 were in a reasonable agreement with the RAD data. However, for deuterons, tritons, and $$\,^{3}{\mathrm{He}}$$ 3 He , the simulations yielded much smaller values than for the corresponding RAD data. In addition, the particles’ spectra within the $$90^{\circ }$$ 90 ∘ zenith angle were also obtained. Based on these spectra, we calculated the radiation dose that would have been received by an average human body on Mars. The distribution of the dose throughout the human body was not uniform. The absorbed and equivalent doses for the brain were the highest among all of the organs, reaching 62.0 ± 1.7 mGy/y and 234.1 ± 8.0 mSv/y, respectively. The average absorbed and equivalent doses for the entire body were approximately 44 mGy/y and 153 mSv/y, respectively. Further analysis revealed that most of the radiation dose was owing to $$\alpha$$ α particles, protons, and heavy ions. We then studied the shielding effect of the Mars soil with respect to the radiation. The body dose decreased significantly with increasing soil depth. At the depth of 1.5 m, the effective dose for the entire body was 17.9 ± 2.4 mSv/y, lower than the dose limit for occupational exposure. At the depth of 3 m, the effective dose to the body was 2.7 ± 1.0 mSv/y, still higher than the accepted dose limit.

The α -decay study is an important tool for obtaining information on the nuclear structure of heavy neutron-deficient nuclei. For the N =126 and 124 isotones with even proton number, an intruder state ( π h 9/2 π f 7/2)8+ based on the attractive interaction of f 7/2 protons and f 5/2 neutrons was observed, which increases the binding energy of this configuration with increasing proton number. Additionally, taking into account the octupole correlations, a large-scale shell model calculations predict that the ( π h 9/2 π f 7/2)8+ state lies close or below the ( π h 9 / 2 2 ) 6+ state in the 216Th and 218U. To extend the systematic of the I π =8+ isomeric state in N =124 isotones and search for the most neutron-deficient uranium isotopes, an experiment for the α -decay studies of 215 - 217U was performed at the gas-filled recoil separator SHANS at the Heavy Ion Research Facility in Lanzhou (HIRFL). Heavy ion induced fusion evaporation reactions of the 180W(40Ar, x n)220 - x U ( x =3 - 5) were used to synthesize these neutron-deficient uranium isotopes. The 40Ar beam was delivered by the sector focusing cyclotron of the HIRFL. The evaporation residues recoiled from the thin target were separated in-flight from the primary beam particles by the gas-filled recoil separator SHANS. After passing through two multi-wire proportional counters, the residues were planted into a focal plane detection system. Based on the energy-position-time correlation measurement, the isotopes 215 - 217U were identified. At a beam energy of 187.2 MeV, two α -decaying states were observed in 216U with E α =8.384(30) MeV, T 1/2=

The axion-like particle (ALP)-photon mixing in the magnetic field around $\gamma$-ray sources or along the line-of-sight could induce oscillation between photons and ALPs, which then causes irregularities in the $\gamma$-ray spectra. In this work we try to search for such spectral irregularities in the spectrum of PKS $2155-304$ using 8.6 years of the Fermi Large Area Telescope (Fermi-LAT) data. No significant evidence for the presence of ALP-photon oscillation is obtained, and the parameter space of ALPs is constrained. The exclusion region sensitively depends on the poorly known magnetic field of host galaxy cluster of PKS $2155-304$. If the magnetic field is as high as $\sim 10~{\rm \mu G}$, the "hole"-like parameter region allowed in Ref.~\cite{Fermi} can be ruled out., Comment: 13 pages, 3 figures, version accepted by Physical Review D

Besides alpha-decay energies and half-lives, more information on nuclear structure properties can be obtained from fine structure observed in a decay. The multi-channel cluster model (MCCM) for well-deformed alpha emitters has very recently been proposed for a precise description of the alpha-decay fine structure. In this paper, based on the neWly proposed Q alpha formula and the predicted rotational energy for superheavy nuclei, we present a theoretical prediction of the fine structure in the alpha decay of deformed Rf, Sg, and Hs isotopes within the MCCM. The branching ratios to various daughter states and total alpha-decay half-lives are evaluated by the five-channels microscopic calculations. Any adjustable parameter is not introduced in our calculations. This is, to our knowledge, the first coupled-channel study of the alpha-decay fine structure in superheavy nuclei. It is expected that the present predictions would be useful for ongoing or future experiments on structure researches of superhezwy nuclei.

It is well known that the spin operators of a quantum particle must obey uncertainty relations. We use the uncertainty principle to study the Larmor clock. To avoid breaking the uncertainty principle, Larmor time can be defined as the ratio of the phase difference between a spin-up particle and a spin-down particle to the corresponding Larmor frequency. The connection between the dwell time and the Larmor time has also been confirmed. Moreover, the results show that the behavior of the Larmor time depends on the height and width of the barrier.

National Natural Science Foundation of China[10705014, 10535010, 10775068, 10675006]; CAS Knowledge Innovation[KJCX2-SW-N02]

We study systematically the average property of fragmentation reaction and momentum dissipation induced by halo-nuclei in intermediate energy heavy ion collisions for different colliding systems and different beam energies within the isospin dependent quantum molecular dynamics model (IQMD). This study is based on the extended halo-nucleus density distributions, which indicates the average property of loosely inner halo nucleus structure, because the interaction potential and in-medium nucleon-nucleon cross section in IQMD model depend on the density distribution. In order to study the average properties of fragmentation reaction and momentum dissipation induced by halo-nuclei we also compare the results for the halo-nuclear colliding systems with those for corresponding stable colliding systems with same mass under the same incident channel condition. We find that the effect of extended halo density distribution on the fragment multiplicity and nuclear stopping (momentum dissipation) are important for the different beam energies and different colliding systems. For example the extended halo density distributions increase the fragment multiplicity but decrease the nuclear stopping for all of incident channel conditions in this paper.

We studied the special roles of loose neutron-halo structure of 19 B on the fragmentation and momentum dissipation by using isospin dependent quantum molecular dynamics. In order to protrude the special roles of neutron-halo structure on the reaction dynamics we compared the fragmentation multiplicity and nuclear stopping (momentum dissipations) induced by neutron-halo nucleus 19 B with those induced by a same mass stable nucleus 19 F under the same incident channel condition. We found that the loose neutron-halo structure of 19 B increases the fragmentation multiplicity in lower beam energy region. On the contrary, the special halo structure of 19 B weakens the nuclear stopping, compared to those induced by stable nucleus 19 F. However both fragmentation multiplicity-difference and nuclear stopping-difference between the reactions induced by 19 B and 19 F gradually decrease and finally disappear as the increase of beam energy. These results suggest a good project for the experimental measurements of the fragmentation multiplicity and nuclear stopping to study the reaction dynamics induced by neutron-halo nuclei.

Radioactive ion beams were produced through the projectile fragmentation induced by 69 MeV/nucleon Ar-36 primary beam on a Be-9\ target. Measurements of reaction cross sections (sigma(R)'s) for 44 nuclei with A < 30 (mostly proton-rich), on carbon were performed on RIBLL (Radioactive Ion Beam Line in Lanzhou) of HIRFL (Heavy Ion Research Facility in Lanzhou) at intermediate energies around 30 MeV/nucleon by a transmission method. The experimental sigma(R) values for Al-23 and P-27 are abnormally large compared with their neighboring nuclei. Together with the previous experimental facts such as the binding energy and ground state data, it suggests anomalously large matter root-mean-square radii and proton halo structure in Al-23 and in P-27. There is an enhancement for the sigma(R) of F-17 + C-12 compared with the neighboring isotopes. Considering that the ground state of F-17 is 1d(5/2), this can indicate that there is a proton skin in F-17. The calculation of relativistic density-dependent Hartree model (RDDH) shows that the nuclei Al-23 and P-27 may have proton-halo structure and F-17 may have proton-skin structure. The significance of these measurements is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

The ground state properties of some superheavy nuclei are calculated using the self-consistent relativistic mean-field (RMF) model. The calculated binding energies of Z=106 isotopes are in good agreement with available experimental ones. The experimental data of alpha decay energies of Z=106 isotopes are also reasonably reproduced by the model. The alpha decay energy and the lifetime on the alpha decay chain of 2 8 2 115 and 2 7 8 113 are predicted based on the RMF calculations and used for comparison with future experiments on new elements Z=113 and Z=115.

Measurements of reaction cross section (sigma(R)) for some proton-rich nuclei (N = 8, 10, 12 isotones) on carbon target at intermediate energies have been performed on RIBLL of HIRFL by a transmission method. The experimental sigma(R) values for Al-23 and P-27 are abnormally large compared with its neighboring nuclei and that of F-17 has an enhancement compared with neighboring isotopes. The calculation of relativistic density-dependent Hartree (RDDH) approach shows there is proton-halo structure in Al-23 and P-27 and there is a proton-skin in F-17. The significance of these measurements was discussed.

The relationship between deexcitation energies of superdeformed secondary minima relative to ground states and the density dependence of the symmetry energy is investigated for heavy nuclei using the relativistic mean field (RMF) model. It is shown that the deexcitation energies of superdeformed secondary minima are sensitive to differences in the symmetry energy that are mimicked by the isoscalar-isovector coupling included in the model. With deliberate investigations on a few Hg isotopes that have data of deexcitation energies, we find that the description for the deexcitation energies can be improved due to the softening of the symmetry energy. Further, we have investigated deexcitation energies of odd-odd heavy nuclei that are nearly independent of pairing correlations, and have discussed the possible extraction of the constraint on the density dependence of the symmetry energy with the measurement of deexcitation energies of these nuclei., 14 pages, 3 figures

The ground state properties of deformed nuclei of C isotope are investigated by the Skyrme-Hartree-Fock theory with new force parameters SK14 of Reinhard and Flocard [Nucl. Phys. A 584 (1995) 467]. Calculations show that the deformed-Skyrme-Hartree-Fock theory with above force parameters provides a good description on the binding energy, the various radii and deformation parameters of C isotope. The figure of the evolution of deformation for whole C isotope chain is plotted. A detailed discussion on numerical results is provided in the paper.

The properties of the s-wave for a quasi-free particle with position-dependent mass(PDM) have been discussed in details. Differed from the system with constant mass in which the localization of the s-wave for the free quantum particle around the origin only occurs in two dimensions, the quasi-free particle with PDM can experience attractive forces in $D$ dimensions except D=1 when its mass function satisfies some conditions. The effective mass of a particle varying with its position can induce effective interaction which may be attractive in some cases. The analytical expressions of the eigenfunctions and the corresponding probability densities for the s-waves of the two- and three-dimensional systems with a special PDM are given, and the existences of localization around the origin for these systems are shown., Comment: 12pages, 8 figures

We develop the method for the calculation of the total reaction cross sections induced by the halo nuclei and stable nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energy. It is extended for nuclear reactions at low energy and intermediate energy by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with the 30 experimental data within 10 percent accuracy.The comparison between the numerical results and the 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies the quite different mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root mean square radii of these nuclei can be extracted from above comparison based on the improved Glauber model, which indicate clearly the halo structures of these nuclei. Especially, it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections induced by the halo nuclei due to the very weak binding and the very extended density distribution., Comment: 15 pages,2 figures. Communucations in Theoretical Physics, (2003) in press

The direct radiative capture process is well described by the spherical potential model. In order for the model to explain direct captures more accurately, the effect of the nuclear deformation has been added and analyzed in this work, since most nucleuses are not spherical. The results imply that the nuclear deformation largely affects the direct capture and should be taken into account during discussing direct capture reactions., 5 pages, 3 figures

The Faddeev equations are solved to investigate the bound states of three-body systems with short-range two-body interactions. Different bound 0+ excited states are obtained depending on the mass ratios of particles, when there is no bound state for two-body sub-systems. On the one hand, a number of bound 0+ excited states appear in the system with two heavy particles and a light particle. On the other hand, a weakly bound 0+ excited state is obtained in the system with two light particles and a heavy particle, which has not been reported in previous works as far as we know.

A gas-filled recoil separator was designed and built newly at Institute of Modern Physics (IMP) in Lanzhou. With the recent commissioning of the separator, the decay properties of 271Ds were studied via the 208Pb (64Ni, n) reaction at a beam energy of 313.3 MeV. One α-decay chain for 271Ds was established in total. The experimental result is consistent with the values reported in the literature.

The unfavored alpha transitions of bismuth isotopes, including the newly observed alpha-decay fine structure in Bi-209 [Beeman et al., Phys. Rev. Lett. 108 (2012) 062501] are investigated by the generalized density-dependent cluster model (GDDCM). Instead of the Wentzel-Kramers-Brillouin barrier penetration probability, the exact solution of the Schrodinger equation under outgoing Coulomb wave boundary conditions is presented. The calculated alpha-decay half-lives are found to be in good agreement with the experimental data for both odd-A and odd-odd nuclei. This indicates that the GDDCM has good applicability for unfavored alpha transitions in addition to favored ones. Some predictions on alpha-decay half-lives are also made for reference in future experiments.

The effect of short-range and tensor correlations on nuclear symmetry energy is investigated by using realistic nuclear momentum distribution n(k). For finite nuclei, the n(k) is discussed in detail within an analytical model that allows inclusion of both short-range and tensor correlation effects in a physically very transparent way. The equation of state of symmetric nuclear matter is calculated by using realistic n(k) parameterization. The tensor-force induced short-range correlations are shown to have a significant impact on the behavior of symmetry energy.

With the recent commissioning of a gas-filled recoil separator at Institute of Modern Physics (IMP) in Lanzhou, the decay properties of (271)Ds (Z = 110) were studied via the Pb-208(Ni-64, n) reaction at a beam energy of 313.3MeV. Based on the separator coupled with a position sensitive silicon strip detector, we carried out the energy-position-time correlation measurements for the implanted nucleus and its subsequent decay alpha's. One alpha-decay chain for (271)Ds was established. The.. energy and decay time of the (271)Ds nucleus were measured to be 10.644 MeV and 96.8 ms, which are consistent with the values reported in the literature.