The 4He(d, αp)n reaction at 12 and 17 MeV

The cross section and the analyzing powers A_y, A_xx and A_yy for the reaction ⁴He($\text{d}$, αp)n are studied with kinematically complete measurements at incident energies of 12 and 17 MeV. Spectral structures due to the final-state interactions and quasifree scattering are measured. A three-body model of the Faddeev type gives a satisfactory fit to the cross-section and A_y data, but it fails to fit adequately the tensor analyzing-power data. The tensor analyzing powers in the breakup process should be sensitive to the input two-body force, and that sensitivity seems to be somewhat greater near the three-body 1⁺ resonance.     

Phenomenological Λ-nuclear interactions

Variational Monte-Carlo calculations have been performed for the ligh s-shell hypernuclei, namely, _Λ ⁴ H, _Λ ⁴ H^*, and _Λ ⁵ He. The main aim of the study has been to give more insight into the Λ-nuclear interactions. Our study shows that the three-body ANN force has a larger share in the splitting energy of _Λ ⁴ H (0⁺–1⁺) compared to the two-body AN force. The analyses on Λ-binding to nuclear matter based on our s-shell results demonstrate that the three-body ANN correlations need to be incorporated suitably to describe these systems.     

Coupled channel method for the π-4He elastic and inelastic scattering

Equations of the coupled channel method written in the momentum space are solved in the K-matrix approach. In this way we are able to consider simultaneously the elastic and inelastic pion-nuclear reactions. Calculated total elastic and total inelastic cross sections are given for several outgoing channels of the reaction⁴He(π ^?,π ^?)⁴He^*. The single-charge-exchange reaction on⁴He is discussed.     

An experimental study of He elastic,inelastic and charge-exchange scattering from Li

A target of ⁶Li was bombarded with the ³He beam from the University of Illinois cyclotron. Differential cross sections for the elastic scattering, the inelastic scattering to the first two excited states of ⁶Li, and the (³He, t) charge-exchange reaction to the ground state of ⁶Be were determined over angular ranges of approximately 20° to 115° (c.m.) at ³He energies of 24.6 MeV and 27.0 MeV. (The weak inelastic transition to the 3.56 MeV state of ⁶Li, ordinarily obscured by a background of three-body break-up, was observed by requiring a coincidence at most angles between the scattered ³He and the ⁶Li recoil.) The ratio of the integrated charge-exchange cross section between 55° and 115° to the integrated inelastic cross section for this transition (both with ΔT = 1) is somewhat less than expected from isospin considerations (i.e., about 1.6 instead of 2.0).     

Coherence effects in low energy Na*(3p)+Na+ scattering: Experiment and semiclassical calculations

Pronounced polarization effects have been observed in inelastic collisions of laser state-prepared Na^*(3p,M _L) with Na⁺ leading to Na^*(3d) for the energy rangeE _CM=20–45 eV. Using linearly polarized light the dependence of the inelastic process on the alignment of the electronic charge cloud of the Na^*(3p) prior to the collision has been measured. In studies with left and right hand circularly polarized light the angular momentum transferred in the collision process has been determined. The results are compared with similar data for the 3p→3s deexitation process studied previously [6]. The density matrix of the Na^*(3p) state has been evaluated with respect to the collisional excitation to Na^*(3d). Semiclassical calculations based on the coupled channel impact parameter approximation using pseudopotentials [7] and nonadiabatic rotational coupling elements for the Na ₂ ^* system [12] have been performed. The agreement with the experimental results is good, in particular for the higher collision energies.     

Interaction potentials and energy transfer cross sections for collisions of metastable helium and neon I: He(23 S)+Ne

Differential cross sections have been measured for He(2³ S)+Ne at kinetic energies between 28 and 370 meV. For energies above 90meV the elastic cross sections show Stückelberg oscillations from curve crossings, which lead to the energy exchange process: He(2³ S)+Ne→He(1¹ S)+Ne(2p ⁵ 4s,3d,4p). Differential cross sections for this inelastic process could be measured above 200 meV. A fit to the data gives the potentials for He(2³ S)+Ne and, less accurately, for He+Ne^*. These results offer a simple explanation, why the exothermic pumping process of the infrared lines of the HeNe laser has a threshold of about 80 meV and a small cross section.     

Search forγ-ray transitions within the5Li groundstate

A search forγ-ray transitions within the broad groundstate of⁵Li has been carried out via the⁴He(p, γp ^*)⁴He reaction atE _p (lab)=1.5?7.0 MeV. Differentially pumped gas targets of the extended and quasi-point types have been used. The results show that the set-up and detection techniques utilized are not sensitive enough to observe such intrastate transitions.     

快放电激励下准分子ArF*和Ar2F*时间谱的研究

本文通过对快放电激励下He/Ar/F₂混合气体中ArF^*,Ar₂F^*时间分辨谱的研究,探讨了准分子ArF^*和Ar₂F^*的形成和猝灭动力学过程。分析表明,ArF^*的时间衰减过程由生成它的主要前态Ar^*的时间变化过程决定,而Ar₂F^*的时间衰减过程则取决于它自己的有效寿命 关键词：     

Pyroelectric and electromechanical properties of the antiferroelectric liquid crystal MHPOBC

We study pyroelectric and electromechanical effects in the prototype antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl-phenyl)4′-octylbiphenil-4-carboxylate (MHPOBC). The linear electromechanical effect in the freely suspended liquid crystal films of MHPOBC has been detected in the broad temperature range inclusive of the antiferroelectric SmC _A ^* as well as paraelectric SmA. The anomalous behavior of the hysteresis loop of SmC _β ^* in the (pyroelectric coefficient, dc bias electric voltage) coordinates has been found.     

He/Ar/Kr/F2混合气体中准分子KrF*和Kr2F*的动力学研究

本文用时间积分谱的方法研究了快放电激励下He/Ar/Kr/F₂混合气体中Kr₂F^*的动力学,探讨了Kr₂F^*形成的通道特性,理论分析和实验结果表明,在快放电激励下,三体碰撞过程KrF^*+Kr+M→Kr₂F^*+M是形成Kr₂F^*的主要通道,而置换反应ArF^*+Kr→KrF^*+Ar又能有效地产生KrF^*。实验测量了Kr₂F^*形成的有关速率常数。 关键词：     

Fragmentation channels of relativistic 7Be nuclei in peripheral interactions

At the JINR Nuclotron, ⁷Li nuclei are accelerated. The charge-exchange reaction involving these nuclei at an external target provides a secondary 1.23-A-GeV ⁷Be beam. This beam is used to irradiate emulsion chambers. The mean free path λ_inel(⁷Be) = 14.0 ± 0.8 cm for inelastic ⁷Be interactions in an emulsion coincides within the errors with those for ⁶Li and ⁷Li nuclei. More than 10% of the ⁷Be events are associated with the peripheral interactions in which the total charge of the relativistic fragments is equal to the charge of the ⁷Be nucleus and in which charged mesons are not produced. An unusual ratio of the helium isotopes is revealed in the composition of the doubly charged fragments of the ⁷Be nuclei: the number of the ³He fragments is twice as large as that of the ⁴He fragments. Each of 50% of peripheral interaction events includes two doubly charged fragments. The channels of the ⁷Be fragmentation into charged fragments are presented. In 50% of events, the ⁷Be fragmentation occurs only into charged fragments without the emission of neutrons. The ⁴He + ³He channel dominates, whereas each of the ⁴He + d + p and ⁶Li + p channels constitutes 10%. Two events without neutron emission are observed in the ³He + t + p and ³He + d + d three-body channels. The mean free path for the coherent dissociation of relativistic ⁷Be nuclei into ⁴He + ³He is equal to 7 ± 1 m. The main features of the fragmentation of relativistic ⁷Be nuclei in such peripheral interactions are explained by the ³He + ⁴He two-cluster structure of the ⁷Be nucleus.     

Elastic scattering of intermediate energy protons on4He and12C

The elastic angular distribution and polarization of ～1 GeV protons on⁴He and¹²C have been analysed using the recently proposed correlation expansion for the Glauber amplitude by retaining terms up to three-body density only. The calculations include Coulomb and spin effects. Using realistic form factors for target nuclei it is found that we need to consider only up to the second-order density term to provide a satisfactory explanation of both kinds of experimental data in the available momentum transfer region. The contribution of the three-body density term is only marginal except in⁴He differential cross-section in the cm angular range 45°<θ _cm<65°.     

Fragmentation of12C nuclei in emulsion at 50 GeV/c

A total of 852¹²C-emulsion nucleus interactions at 4.2 GeV/c per incident nucleon was investigated. At least one charged projectile fragment was observed in 733 events, in which the multiplicity and angular distributions ofZ=1,2, and ≧3 projectile fragments were studied. Five events were observed in which¹²C projectile nuclei were fragmented into twoZ=3 fragments. Thus the cross section of this process is about 6×10^?3 of the inelastic cross section. The angular distribution of projectile fragments becomes narrower as the fragment charge increases. At all values of fragment charges, a pronounced peak in the angular distribution can be observed at zero emission angle. In this paper, only the projectile-fragmentation events possessing no heavily ionizing particle (n _h =0 events) have been investigated. Our sample contains 84 of these events, i.e., about 10% of the total inelastic events. The number of events withZ _max, the charge of the emitted principal fragment, equal to 1, 2, 3, 4, and 5 are 11, 52, 13, 4, and 4, respectively. Of these 84 events, 36 interactions have a total charge of emitted projectile fragmentsZ ^* equal to 6, i.e., as much as the beam chargeZ _p . Of the 36 events, 17 produce no charged pions and of the 17 events, 10 only represent the dissociation of¹²C→3α, i.e., 1.2% of the total inelastic interactions. The number of events withZ ^*=5, 4, 3, 2, and 1 are 27, 14, 4, 2, and 1, respectively. The average number of produced charged pions per one interacting projectile nucleon was estimated to be 1.2±0.1. This value agrees with the corresponding one in elementary interaction at the same energy per nucleon, a result pertaining to the incoherent production model in collision of two nuclei. In this class of events,n _h =0, the number of stars in which H, He, Li, Be, and B isotopes were detected are 59, 58, 13, 4, and 4, respectively. The projected angular distributions ofZ=1 and 2 projectile fragments are Gaussian shaped, narrow, consistent with isotropy, and depend on the fragment. These distributions are consistent with quantum mechanical calculations using the sudden approximation and shell-model functions. From the angular measurements ofα-particle tracks in the dissociation¹²C→3α events, the distribution ofα-particle transverse momentum inside the carbon projectile nucleus was deduced. It seems that the dissociation of¹²C→3α happens via an intermediate⁸Be state.     

Content and Isotope Ratios of Noble Gases in Congelation Ice of Lake Vostok

Isotope ratios of noble gases (He, Ne, Ar) were studied in samples collected by degassing of cores of water frozen over a glacier of Lake Vostok. The gases were collected into glass retorts during three days of degassing of cores, which have just been extracted from the borehole. Within the error, the isotope ³He/⁴He ratios of 0.28 ± 0.08 R_A (R_A = 1.38 × 10^–6 is the ratio for air) correspond to those from [1]. The ⁴He/²⁰Ne and ⁴⁰Ar/³⁶Ar ratios (12.4 ± 4.6 R_A and 1.0074 ± 0.0023 R_A, respectively) exceed their contents in air (⁴He/²⁰Ne_A = 0.29; ⁴⁰Ar/³⁶Ar_A = 298.6) and may indicate some contribution of terrigenous gas to the gaseous balance of the lake, as well as the high content of ancient ground waters in the lake. The ³He/⁴He ratio of 0.28 R_A means low mantle ³He flux typical of continental platforms far from active rift zones.     

Inelastic p 4He interaction in nonequilibrium cosmological nucleosynthesis

The current status of experimental data on inelastic p ⁴He scattering is reviewed, and the cross sections for respective channels are roughly estimated. These estimates make it possible to compute the amounts of ³He, ³H, and d nuclei produced in nonequilibrium cosmological nucleosynthesis to a precision of 10%. Investigation of inelastic p ⁴He scattering by using the method of accelerated ⁴He nuclei at E _p75 MeV is of particular interest for cosmological applications because this allows one to achieve a higher precision in calculating nonequilibrium cosmological nucleosynthesis.     

Solving the differential Yakubovsky equations for p 3He scattering by the cluster-reduction method

The cluster-reduction method has been used to solve numerically the differential equations for the s-wave Yakubovsky components in the nppp system. Proton scattering on a ³He nucleus has been considered for energies below the three-body threshold in the singlet and triplet spin states of the system. Nucleon-nucleon interaction has been simulated by the MT I–III potential, and the Coulomb interaction between the protons has been taken into account. Effective equations that describe the relative motion of clusters have been derived. The low-energy behavior of phase shifts has been analyzed. The values of ¹ A=8.2 fm and ³ A=7.7 fm have been obtained for, respectively, the singlet and triplet scattering lengths. The calculated phase shifts agree well with experimental data.     

Constrained variational calculations of closed shell nuclei with the reid potential

Lowest-order constrained variational calculations with harmonic oscillator wave functions are carried out for ⁴He, ¹⁶O, and ⁴⁰Ca nuclei with the Reid potential. The results obtained with this simple method are in very close agreement with those obtained by renormalized Brueckner-Hartree-Fock theory with orthogonalized plane wave intermediate states. The A-dependence of the difference between the experimental and calculated binding energies for A = 2, 3, 4, 16, 40 and ∞ can be explained by a three-body cluster term coming either from a wrong off-energy-shell behavior of the Reid potential or a three-body force. The calculated radii of ¹⁶O and ⁴⁰Ca are ≈ 10% too small, indicating that the Reid potential may not be very realistic.     

The quasi-free 3He(e,e′p) reaction

The proton spectral function has experimentally been determined with the ³He(e, e′p) reaction for missing energies, 0<E_m<70MeV, and recoil momenta, 0<P_B<310 MeV/c. Experimental results are obtained for both the two-body, ³He(e, e′p)²H, and three-body breakup processes. Proton momentum density distributions, obtained in a PWIA analysis, are compared with theoretical calculations: Faddeev solutions with the RSC and Paris potentials, and variational calculations with various potentials, including those with a three-nucleon interaction term. Energy-weighted sum rule results are presented and compared with theoretical predictions. The coincidence cross sections are also compared with calculations which include the effects of final state interactions and meson exchange currents. Consistency of the results with PWIA is investigated in the framework of the Chew-Low extrapolation procedure.     

Statistical analysis of24Mg+24Mg elastic and inelastic scattering

The data on the excitation functions of²⁴Mg+²⁴Mg elastic and inelastic (²⁴Mg +²⁴Mg^*(2⁺),²⁴Mg^*(2⁺)+²⁴Mg^*(2⁺),²⁴Mg+²⁴Mg^*(4⁺),²⁴Mg^*(4⁺)+²⁴Mg^*(2⁺),²⁴Mg+²⁴Mg^*(6⁺)) scattering fromE _c.m=42 to 56 MeV have been subjected to a statistical analysis consisting of calculations of deviation function, cross-correlation function, cross-channel correlation coefficients, coherence widths, and the distribution of cross sections. On the basis of the analysis resonant structures atE _c.m=45.70, 46.65, 47.35 and 47.75 MeV have been confirmed. Two new resonant structures atE _c.m=44.55 and 50.50 MeV have been identified.     

Dynamic deformation of light nuclei in excited states

An important property—the dynamic deformation of B* light aligned nuclei—is investigated for the nuclear reactions A(x, y)B* → γ + B ₀ by measuring the y-γ correlations. Dynamic deformation is determined from the orientation tensors of multipolar moments. Normalization constants of the contributions from even-rank orientation tensors are determined from the condition of coincidence between dynamic and static deformations of the B* nucleus for θ _y = 0°. Experimental dynamic deformations of ¹²C(2⁺) nuclei caused by the inelastic scattering of α particles and deuterons are determined, along with the ¹⁰Be(2⁺) nuclei formed in reaction ⁹Be(d, p)¹⁰Be(2⁺). It is shown that the dynamic deformation of the aligned nuclei depends on how they are formed and their structure, and evolves substantially when the angle θ _y is varied.