Ξ^-t quasibound state instead of ΛΛnn bound state

The coupledΛΛnn-Ξ-pnn system was studied to investigate whether the inclusion of channel coupling is able to bind theΛΛnn system.We use a separable potential three-body model of the coupledΛΛnn-Ξ-pnn system and a variational four-body calculation with realistic interactions.Our results exclude the possibility of aΛΛnn bound state by a large margin.Instead,we found aΞ-t quasibound state above theΛΛnn threshold.     

Dirac equation for the Hulthén potential within the Yukawa-type tensor interaction

Using the Nikiforov-Uvarov (NU) method, pseudospin and spin symmetric solutions of the Dirac equation for the scalar and vector Hulthén potentials with the Yukawa-type tensor potential are obtained for an arbitrary spin-orbit coupling quantum number κ. We deduce the energy eigenvalue equations and corresponding upper- and lower-spinor wave functions in both the pseudospin and spin symmetry cases. Numerical results of the energy eigenvalue equations and the upper- and lower-spinor wave functions are presented to show the effects of the external potential and particle mass parameters as well as pseudospin and spin symmetric constants on the bound-state energies and wave functions in the absence and presence of the tensor interaction.     

Cross section measurements for (n, 2n),(n, α)(n,p), and reactions on rhenium isotopes around 14 MeV neutrons and their theoretical calculations of excitation functions

Cross-section data of the ~(185)Re(n,2 n)~(184)mRe,~(185)Re(n,2 n)~(184)Re,~(185)Re(n,α)~(182 m14+m2+g)Ta,~(187)Re(n2 n)~(186 g,(m))Re,~(187)Re(n,α)~(184)Ta,and ~(187)Re(n,p)~(187)W reactions were measured at four neutron energies,namely 13.5,14.1,14.4,and 14.8 MeV,by means of the activation technique,relative to the reference cross-section values of the~(93)Nb(n,2 n)~(92 m)Nb reaction.The neutrons were generated from the T(d,n)~4 He reaction at the K-400 Neutron Generator at China Academy of Engineering Physics.The induced y activities were measured using a high-resolution γ-ray spectrometer equipped with a coaxial high-purity germanium detector.The excitation functions of the six abovementioned nuclear reactions at neutron energies from the threshold to 20 MeV were calculated by adopting the nuclear theoretical model program system Talys-1.9 with the relevant parameters properly adjusted.The measured cross sections were analyzed and compared with previous experiments conducted by other researchers,and with the evaluated data of BROND-3.1,ENDF/B-Ⅷ.0,JEFF-3.3,and the theoretical values based on Talys-1.9.The new measured results agree with those of previous experiments and the theoretical excitation curve at the corresponding energies.The theoretical excitation curves based on Talys-1.9 generally match mo st of experimental data well.     

Activation cross-sections of titanium isotopes at neutron energies of 13.5–14.8 MeV

The cross-sections for ~(46) Ti(n,2 n)~(45) Ti, ~(46) Ti(n,p)~(46 m+g) Sc+~(47) Ti(n,d*)~(46 m+g) Sc, ~(46)Ti(n,p)~(46 m+g) Sc, ~(47) Ti(n,p)~(47) Sc+~(48) Ti(n,d*)~(47) Sc, ~(47) Ti(n,p)~(47) Sc, ~(48) Ti(n,p)~(48) Sc+~(49) Ti(n,d*)~(48) Sc,~(48) Ti(n,p)~(48) Sc, and ~(50) Ti(n,α)~(47) Ca reactions were investigated around neutron energies of 13.5–14.8 Me V by means of the activation technique. Fast neutrons were produced by the~3 H(d,n)~4 He reaction. Neutron energies from different directions in the measurements were obtained in advance using the method of cross-section ratios for ~(90) Zr(n,2 n)~(89 m+g) Zr and ~(93) Nb(n,2 n)~(92 m) Nb reactions. The results obtained are analyzed and compared with the experimental data provided by the literature and verified nuclear data in the JEFF-3.3,CENDL-3.1, ENDF/B-VIII.0 libraries, as well as results calculated by Talys-1.9 code.     

Measurements of differential and angle-integrated cross sections for the ~(10)B(n, α)~7Li reaction in the neutron energy range from 1.0 eV to 2.5 MeV

Differential and angle-integrated cross sections for the ~(10)B(n,α)~7 Li,~(10)B(n,α_0) ~7 Li and ~(10)B(n,α_1) ~7 Li~*reactions have been measured at CSNS Back-n white neutron source.Two enriched(90%) ~(10)B samples 5.0 cm in diameter and～85.0 μg/cm~2 in thickness each with an aluminum backing were prepared,and back-to-back mounted at the sample holder.The charged particles were detected using the silicon-detector array of the Light-charged Particle Detector Array(LPDA) system.The neutron energy En was determined by TOF(time-of-flight) method,and the valid a events were extracted from the E_n-Amplitude two-dimensional spectrum.With 15 silicon detectors,the differential cross sections of a-particles were measured from 19.2°to 160.8°.Fitted with the Legendre polynomial series,the(n,a) cross sections were obtained through integration.The absolute cross sections were normalized using the standard cross sections of the ~(10)B(n,α) ~7 Li reaction in the 0.3-0.5 MeV neutron energy region.The measurement neutron energy range for the ~(10)B(n,α) ~7 Li reaction is 1.0 eV≤E_n 2.5 Me V(67 energy points),and that for the ~(10)B(n,α_0) ~7 Li and~(10)B(n,α_1) ~7 Li~*reactions is 1.0 eV≤E_n1.0 MeV(59 energy points).The present results have been analyzed by the resonance reaction mechanism and the level structure of the ~(11)B compound system,and compared with existing measurements and evaluations.     

轻核(n,x)反应微分截面的实验测量

对本课题组十几年来的(n,x)反应实验研究工作进行了评述.介绍了屏栅电离室的特点、构造与工作原理.用屏栅电离室在北京大学4.5MV静电加速器上测量了1—7MeV中子6Li(n,t)4He和10B(n,α)7Li反应的微分截面与截面,对实验结果进行了讨论. Our research work on (n, x) reaction for more than one decade is reviewed. The characteristics, structure, and working principle of the gridded ionization chamber are discussed. Differential cross sections and cross sections of the~(6)Li(n, t)~(4)He and~(10)B(n, α)~(7)Li reactions were measured in the neutron energy range of 1—7 MeV by using the GIC method. Experiments were carried out at the 4.5 MV Van de Graaff accelerator of Peking University. Results of the measurement are discussed.     

Determination of neutron capture cross sections of ~(232)That 14.1 MeV and 14.8 MeV using the neutron activation method

The ~(232)Th(n,γ)~(233)Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method.The neutron flux was determined using the monitor reaction~(27)Al(n,α)~(24)Na.The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector.The experimentally determined cross sections were compared with the data in the literature,and the evaluated data of ENDF/B-Ⅶ.1,JENDL-4.0u+,and CENDL-3.1.The excitation functions of the ~(232)Th(n,γ)~(233)Th reaction were also calculated theoretically using the TALYS1.6 computer code.     

Difficulties in probing density dependent symmetry potential with the HBT interferometry

Based on the updated UrQMD transport model,the effect of the symmetry potential energy on the two-nucleon HBT correlation is investigated with the help of the coalescence program for constructing clusters,and the CRAB analyzing program of the two-particle HBT correlation.An obvious nonlinear dependence of the neutron-proton(or neutron-neutron) HBT correlation function(Cnp,nn) at small relative momenta on the stiffness factor γ of the symmetry potential energy is found:when γ 0.8,Cnp,nn increases rapidly wit...     

Joint transfer of time and frequency signals and multi-point synchronization via fiber network

A system of jointly transferring time signals with a rate of 1 pulse per second(PPS) and frequency signals of 10 MHz via a dense wavelength division multiplex-based(DWDM) fiber is demonstrated in this paper.The noises of the fiber links are suppressed and compensated for by a controlled fiber delay line.A method of calibrating and characterizing time is described.The 1PPS is synchronized by feed-forward calibrating the fiber delays precisely.The system is experimentally examined via a 110 km spooled fiber in laboratory.The frequency stabilities of the user end with compensation are1.8×10~(-14) at 1 s and 2.0×10~(-17) at 10~4 s average time.The calculated uncertainty of time synchronization is 13.1 ps,whereas the direct measurement of the uncertainty is 12 ps.Next,the frequency and 1PPS are transferred via a metropolitan area optical fiber network from one central site to two remote sites with distances of 14 km and 110 km.The frequency stabilities of 14 km link reach 3.0×10~(-14) averaged in 1 s and 1.4×10~(-17) in 10~4 s respectively;and the stabilities of 110 km link are 8.3×10~(-14) and 1.7×10~(-17),respectively.The accuracies of synchronization are estimated to be 12.3 ps for the14 km link and 13.1 ps for the 110 km link,respectively.     

Theoretical Prediction of Diamond Betavoltaic Batteries Performance Using ~(63)Ni

A diamond p–n junction is used to convert the decay energy of ~(63)Ni source into electrical energy. The selfabsorption effect of the ~(63)Ni source, the backscatter process and the transport process of beta particles in diamond materials are studied. Then the theoretical maximum of electrical properties and the energy conversion efficiencies of diamond-~(63)Ni p–n junction batteries are achieved. Finally, a feasible design of p~+p~-n~+junction battery, which has the maximum output power density of 0.42 μW/cm~2 and the optimal device conversion efficiency of 26.8%,is proposed.     

Electromagnetic form factors of Λ_c in the space-like momentum region

We studied the electromagnetic form factors(EMFFs) of Λ_c and the contributions of the quark and diquark currents to the EMFFs of Λ_c in the space-like region in the Bethe–Salpeter equation approach with instantaneous approximation. In this picture, baryon Λ_c can be regarded as a two-body c(ud) system. We found that for different values of parameters the contribution of quark and diquark currents to the EMFFs of Λ_c is very different,while their total contribution to the EMFFs of Λ_c is similar. The EMFFs of Λ_c are similar to those of other baryons(proton, Ξ~-, and Σ~+) with a peak at ω = 1, where ω = v′·v is the velocity transfer between the initial state(with velocity v) and the final state(with velocity v′) of Λ_c.     

Corrections to the impulse approximation for π−d→nnγ

Corrections to the impulse approximation for π^?d→nnγ are calculated. The results substantiate the conclusions of McVoy and of Bander, that the energy dependence of the amplitude is determined precisely by the neutron-neutron ¹S₀ final state interaction. Corrections to the normalized spectrum are less than 2% up to nn energies greater than 1 MeV.     

Neutron-neutron effective range from quasifree scattering 2H(n,nn)p at 25 MeV

A neutron coincidence spectrum from the deuteron breakup ²H(n, nn)p was measured at the kinematical condition of quasifree neutron-neutron scattering with 25 MeV neutrons in the entrance channel. The efficiencies of both scintillation detectors were calibrated in the same experimental arrangement as the breakup measurement was performed. The neutron flux was monitored by a proton recoil telescope. Absorption, double scattering and geometric conditions have been simulated by the Monte Carlo technique. From a fit based on the Ebenhöh-Bruinsma-Stuivenberg code with the neutron-neutron scattering length a_nn = ?16.6 fm for the effective range, the value r_{nn = 2.69 ± 0.27 fm} was determined.     

Action du champ cristallin sur l'ion Er3+ dans l'oxysulfure de terre rare Er2O2S

The Er³⁺ electronic ion structure, in its 4f¹¹ configuration, has been determined by the optical absorption spectrum of Er₂O₂S. By the use of the Slater parameters F₂ = 424,4, F₄ = 66,1, F₆ = 6,87 cm^?1 and the Spin-orbit parameter ζ = 2367 cm^?1, the experimental ‘free-ion’ energy levels have been fitted with a r.m.s. deviation of 78 cm^?1. In intermediate coupling, the crystal field parameters V₂⁰ = 90, V₄⁰ = 175, V₄³ = 2365, V₆⁰ = 0,5, V₆³ = 205 and V₆⁶ = 180 cm^?1 give the best fit with experimental data. For 56 Stark levels involved the calculation predicts the splittings with a r.m.s. deviation of 12 cm^?1. The magnetic susceptibility has been calculated and is in satisfactory agreement with experimental powder measurements.     

Vibrational spectra and force constants of symmetric tops: Rotational analysis of ν3 and 2ν3 of H3Si35Cl and H3Si37Cl

The gas-phase infrared spectra of natural and ³⁵Cl isotopically enriched H₃SiCl have been recorded with a resolution of 0.04 cm^?1 in the regions of ν₃ (～550 cm^?1) and 2ν₃ (～1100 cm^?1). The fundamentals of species with ²⁸Si, ²⁹Si, ³⁰Si, ³⁵Cl, and ³⁷Cl and several hot bands of the series nν₃ + mν_i ? mν_i (n, m = 1, 2; i = 3 and 6) have been detected. The parameters ν₀, x₃₃, x₃₆, B₀, α₃^A, D_J⁰ and D_J³ were determined by a combination of least-squares analysis of P and R branches resolved into J peaks (J ≤ 90) and a band contour simulation. Possible resonances of nν₃ and (n ? 1)ν₃ + ν₆ are discussed.     

New analysis of the ν2, ν3, ν4, and ν6 bands of formaldehyde H2 CO line positions and intensities in the 5-10 μm spectral region

This work, besides its fundamental interest is mainly motivated by the atmospheric importance of formaldehyde. The 10-μm region is indeed a possible spectral domain for the detection of this molecule in the atmosphere and no line parameters are presently available in the atmospheric databases for H₂CO in this spectral range. Using the experimental data available in the literature for the ν₃, ν₄, and ν₆ bands [J. Chem. Phys. 91 (1989) 646 and references therein] and for the ν₂ band [J. Mol. Spectrosc. 96 (1982) 353 and references therein] and adequate theoretical models it proved possible to reproduce satisfactorily the experimental data and to generate a list of line positions and intensities for the 5-10 μm region. The Hamiltonian model accounts for the various Coriolis-type resonances which perturb the energy levels of the 3¹, 4¹, and 6¹ vibrational states as well as for the weaker anharmonic resonances coupling the 2¹ and 3¹ energy levels. This is also the case for the line intensity calculations which allow one to reproduce satisfactorily the line by line intensity measurements as well as the integrated intensities available in the literature.     

Medium effects in ΛK~+ pair production by 2.83 GeV protons on nuclei

We study ΛK~+ pair production in the interaction of protons of 2.83 GeV kinetic energy with C, Cu,Ag, and Au target nuclei in the framework of the nuclear spectral function approach for incoherent primary proton–nucleon and secondary pion–nucleon production processes, and processes associated with the creation of intermediate Σ~0K~+ pairs. The approach accounts for the initial proton and final Λ hyperon absorption, final K~+ meson distortion in nuclei, target nucleon binding, and Fermi motion, as well as nuclear mean-field potential effects on these processes.We calculate the Λ momentum dependence of the absolute ΛK~+ yield from the target nuclei considered, in the kinematical conditions of the ANKE experiment, performed at COSY, within the different scenarios for the Λ-nucleus effective scalar potential. We show that the above observable is appreciably sensitive to this potential in the low-momentum region. Therefore, direct comparison of the results of our calculations with the data from the ANKE-at-COSY experiment can help to determine the above potential at finite momenta. We also demonstrate that the two-step pion–nucleon production channels dominate in the low-momentum ΛK~+ production in the chosen kinematics and, therefore, they have to be taken into account in the analysis of these data.     

Laser stark spectroscopy of the ν4 + ν8 − ν8 band of CH3C15N: Fermi resonances with 4ν84, 4ν82, and (ν7 + ν8)2

Laser Stark spectra for the ν₄ + ν₈ ? ν₈ parallel band of CH₃C¹⁵N were measured by using CO₂ and N₂O lasers in the 10-μm region. About 300 resonances have been assigned to 102 rovibrational transitions with J′ <- 16 and ?9 ≤ kl ≤ +9. Anomalies observed around kl = ?6 and +8 were proved to be due to the Fermi interactions with 4ν₈² and 4ν₈⁴, respectively. Another Fermi interaction with (ν₇ + ν₈)² was necessary to account for the anomaly around kl = ?6. Observed data were analyzed by the method of least squares, and precise molecular constants have been obtained.     

Neutron-neutron quasifree scattering in the 2H(n,nn)p reaction at En = 14.1 MeV

Neutron-neutron quasifree scattering has been studied in the deuteron break-up reaction ²H(n, nn)p at E_n = 14.1 MeV. Two coplanar and symmetric configurations have been investigated in a kinematically complete experiment where the detection of the spectator particle was not possible. The experimental cross sections are compared with “exact” calculations derived from Faddeev-type equations solved with S- and P-wave nucleon-nucleon separable interactions. These calculations agree both in shape and magnitude with the differential cross section for the θ₁ = ? θ₂ = 40° configuration (E_p^min = 0). At θ₁ = ? θ₂ = 30° (E_p^min = 180 keV). however, the absolute value of the measured cross section is too high and an observed structure in the shape of the differential cross section is in sharp conflict with the now available “exact” calculations.     

Search for a narrow resonance in 6Be with the 4He(3He,n) reaction

The ⁴He(³He, n)⁶Be reaction has been investigated at 36.20 MeV bombarding energy in search for a narrow resonance near the ³He-³He threshold which has been proposed as a possible explanation for the missing solar neutrinos in Davis' experiment. Neutrons have been detected at θ_b = 0° with an effective resolution < 25 keV in the c.m. system, in coincidence with protons emitted at θ_p = 50°. No indication for the existence of such a resonance has been found and an upper limit (dσ/dω)_res ≦ 7.5 μb/sr has been established.