The role of tensor forces in Fermi liquid theory

We study the effect of tensor forces on the Fermi liquid parameters in nuclear matter. The usual stability conditions in the σ₁ · σ₂and σ₁ · σ₂τ₁ · τ₂ channels are found to be appreciably modified by tensor forces. We present Fermi liquid parameters for the Reid soft-core potential corrected for the proper inclusion of tensor forces.     

Polarization fluctuations in regions bounded by equi-potentials

It is shown that the integral of <{P(rτ), P(r')}>· n? as a function of r over a volume V_e bounded by an equi-potential is independent of r' and of V_e and is determined solely by [?(ω)?1] · n? provided the dielectric constant is local and that V_e is of macroscopic dimensions.     

Correlation inequality in Heisenberg ferromagnet

In a four-spin Heisenberg ferromagnetic system, it is found computationally that Griffiths' second inequality, ?〈σ_r·σ_s〉/?J_mn?0, m, n, r, s distinct, is violated, and conditions are obtained under which it holds.     

Pion condensation in symmetric nuclear matter

The problem of pion condensation in isospin symmetric nuclear matter is investigated in the framework of the σ-model with a residual nucleon-nucleon interaction (g′σ₁ · σ₂τ₁ · τ₂δ(x)) and Δ-isobars. The equation of state for the pion condensed phase is calculated and applied to a low-energy heavy-ion collision in the TDHF approximation. The effective particle-hole interaction and the response to spin-isospin excitation are used to determine the magnitude of the Landau-Migdal parameter g′. For a reasonable range of g′(0.5 < g′ ≦ in units of g²/4m²_N = 410 MeV · fm³) pion condensation occurs at densities above normal nuclear matter density and leads to an equation of state with no stable density isomer.     

Ferroelectric and optical properties of Ba6Ti2Nb8O30 single crystals

The dielectric, optical and non-linear optical properties of Ba₆Ti₂Nb₈O₃₀ single crystals were examined from room temperature up to the Curie temperature of 245°C. The spontaneous polarization at room temperature was estimated as 0·22±0·01 C/m². The linear electrooptic constants were measured as r₃₃^T=(1·17±0·02)×10^?10 and r₁₃^T=(0·42±0·01)×10^?10 m/V. The non-linear optical coefficients were d₃₃=(15·1±2·0)×10^?12 and d₃₁=(11·0±2·0)×10^?12 m/V, which are comparable to those of Ba₄Na₂Nb₁₀O₃₀. Temperature dependences of δ₃₃ and δ₃₁ (Miller's δ) were found to be proportional to that of P_s.     

Search for heavy quasistable leptons

Negative results of a search for heavy quasistable charged leptons at the IHEP accelerator are reported. For the selection of heavy leptons a system of scintillation and gas ?erenkov counters was used. The upper limit estimations of the differential cross sections for heavy lepton production in pN collisions at E_p = 70 GeV are, for example, d²σ/dpω (p = 30 GeV/c, θ = 2 mrad, 1 ? M_λ ? 4.8 GeV) = 4.10^?38 cm²/sr · GeV. The results of the present work, together with the data on muon pair production in nucleon-nucleon interactions, show that there are no heavy charged leptons with masses from 0.55 GeV (τ_λ > 7 · 10^?10 sec) up to 4.5 GeV (τ_λ > 3 · 10^?8 sec).     

Die kristallisationsgeschwindigkeit des bestrahlten glasigen selens

At the temperature of 90°C the crystallization rate of γ-irradiated (0–154.5 Mrad) vitreous selenium has been studied by the calorimetric method. The obtained results satisfy the Avrami's equation x = 1 ? exp(? L·C_Kr·τ^z). It was found that radiation induced changes of vitreous selenium structure bring about the decrease of the exponent z and the increase of the value L·c_Kr.The relationship between the above results and structural changes of vitreous selenium was discussed.     

Measurement of the Baryon-exchange reactions K−p→Λη, K−p→Λπ0 at 6 GeV/c and the value of the ηNN coupling constant

In order to determine the ηNN coupling constant we have measured the two reactions K^?p→Λη and K^?p→Λπ⁰ with a magnetic wire chamber spectrometer which contained a gamma counter for the γγ decays of π⁰ and η. The Λ polarization and the differential cross sections are given. The latter have quite different u dependences. Their ratio is interpreted, in terms of a nucleon-Regge exchange model, as the effect of a small ηNN coupling constant for which we obtain G_ηNN² = G_πNN² · (0.26 ± 0.10) as allowed by SU(3). The large value given by Heisenberg's non-linear field theory, G_ηNN² = G_πNN² · 0.9, is excluded by this measurement if the characteristic u dependence of the Λπ⁰ channel is attributed to N_α Regge exchange.     

Mean lifetimes of excited levels of Ar II. I. Time correlation measurements

Mean Lifetimes of excited levels of Ar II have been measured using the method of time-correlated photons in cascade. The following results were obtained: for 4p⁴S^°_{$\text{3}\text{2}$}, τ = 7·2±0·3ns; for 4p′²F^°_{$\text{7}\text{2}$}, τ = 8·8±0·2 ns; for 4p′²F^°_{$\text{5}\text{2}$}, τ = 8·0±0·2 ns. These results are compared with experimental and theoretical values.     

Photoinduced electron transfer of Rhodamine 6G/N,N-diethylaniline revealed by multiplex transient grating and transient absorption spectroscopies

The dynamics and spectroscopic characteristics of the ultrafast photoinduced electron transfer (ET) of Rhodamine 6G (Rh6G⁺) in N,N-diethylaniline (DEA) were studied using femtosecond time-resolved multiplex transient grating and transient absorption spectroscopies. The ultrafast photoinduced forward ET from DEA to the Rh6G⁺* cation radical excited state has a time constant of τ _FET = 219–318 fs. The much slower backward ET from the neutral radical Rh6G^· to DEA⁺ with a time constant of τ _BET = 22.76–42.31 ps occurs in the inverted region. Intramolecular vibrational relaxation of the excited state takes place in τ _IVR = 2.18–6.91 ps.     

On the calculation of the orientational correlation parameter g 2

The g ₂ factor for a model of liquid carbon disulphide has been calculated by molecular dynamics simulation. The values of g ₂ for the model at three points along the orthobaric curve are: 1·17 ± 0·04 (298 K), 1·27 ± 0·03 (245 K), 1·39 ± 0·06 (193 K). These values are in good agreement with available experimental values. By calculating g ₂ in shells of cubic symmetry it is found that the value of g ₂ is determined by the orientational correlation of a molecule with neighbours within a few (two to three) molecular diameters. Spurious orientational correlations are introduced by the periodic boundary conditions and the calculation of collective correlation functions by averaging over the whole cube is shown to be unreliable. A theoretical calculation of g ₂ using RISM + SSA fails to reproduce the state dependence of the g ₂ values calculated from the simulation. This failure is not due to the small differences between the simulation and RISM g _αβ(r) for r < 4·5 Å but to inaccuracies in the SSA in the intermediate region r ～ 6 Å.     

Structural and magnetic properties of the Dy1−xThxFe3 system and some compounds of the form M0·1Th0·9Fe3

The structural and magnetic properties of the pseudobinary Dy_1?xTh_xFe₃ system, crystallizing in PuNi₃ type structure, have been investigated. For x<0·4 the magnetization vs temperature behavior can be understood on a ferrimagnetic coupling between the dysprosium and iron sublattices. For X=0·6 to 0·9 the magnetization vs temperature data show a marked transition at temperatures above 100°K. Lattice constants indicate a discontinuity in the lattice parameter c between X=0·6 and 0·5. Similar anomalies in the M vs T behavior were observed in M_0·1Th_0·9Fe₃ (where M=Sc, Y, Pr, Lu) compounds. These results can be explained on the basis of Friedel's model of transition metal d-bands.     

Magnetic Resonance Imaging of Diffusion in the Presence of Background Gradients and Imaging of Background Gradients

The measurement of the self-diffusion coefficient D by an NMR technique that uses an applied gradient G_A can be corrupted by systems that have a background magnetic field gradient G₀ and also by imaging gradients G₁, when used in an imaging mode. In a nonimaging mode, the corrupting cross term G_A · G₀can be eliminated in the diffusion measurement by use of an alternating-pulse-field-gradient (APFG) sequence that allows an accurate and uncorrupted measurement of D. A Carr-Purcell echo train enables the measurement of the expectation value, 〈DG²₀〉; assuming D and G₀ to be uncorrelated will allow 〈G²₀〉 to be determined. An image of D or of 〈DG²₀〉 may be obtained without the corrupting G_A · G₀ and G_A · G_I terms by appending a standard imaging sequence to an APFG sequence or a Carr-Purcell sequence, respectively; assuming D and G₀ to be uncorrelated will allow (〈G²₀〉 to be determined within each pixel. Measurements of D and 〈G²₀〉 and their images are made in apple flesh in which minute air bubbles are shown to produce the large 〈G²₀〉. Their values in an 81 g Golden Delicious apple at a measuring frequency of 100 MHz were D = 1.42 × 10⁻⁵ cm²/s and [formula] = 8.9 G/cm.     

1+ state and effective g-factor

The effects of nuclear field r²(Y₂σ₁)_1υ on magnetic properties of single-particle states in odd-A nuclei (^208±1Pb) are considered. The coupling constant associated with this type of field is estimated by an argument that realtes it to the coupling constant for the field (γ₀σ₁)_1υ. The effects of including the r²(Y₂σ₁)_1υ field on the M1 moments and transitions are estimated.     

Coulomb excitation of 182, 184, 186W and 166Er with 4He and 16O ions

The Coulomb excitation reaction induced by ⁴He ions selectively excites 2⁺ and 3^? states by direct E2 and E3 Coulomb excitation. In this paper, we present new results from γ-ray spectroscopy with 15 MeV ⁴He ions on a natural abundance target of W. In particular, a 3^? state in each isotope, ^{182, 184, 196}W, was observed by direct E3 excitation. In addition to obtaining B(Eλ, 0 → J = λ) for excitation of each state, information on the reduced transition probabilities for the different decay modes of these states is given. The Coulomb excitation probabilities of the 2'⁺ states at 786 keV in ¹⁶⁶Er and at 737 keV in ¹⁸⁶W were measured with ¹⁶O and ⁴He ions by the backscattered particle-gamma coincidence method in order to determine the static electric quadrupole moment Q_2'. We obtain for ¹⁶⁶Er Q_2' = 2.11 ± 0.37 e· b which is in agreement with (Q_2')_rot and for ¹⁸⁶W Q_2' = 1.17 ± 0.30 e · b which is in agreement with Kumar-Baranger model calculations and is significantly smaller than (Q_2')_rot. This deviation of the measured Q_2' from (Q_2'rot implies in the framework of the Kumar-Baranger calculations a strong coupling between β- and γ-vibrational bands. On the other hand, our observed upper limit for B(E2,2″ → 2′) does not confirm this implication.     

Interatomic force constants studies of AMF3perovskite-type crystals (A = K,Rb; M = Mg,Ni, Co,Zn, Mn)

A simple model involving only three force constants allows us to evaluate the short range interactions in perovskite fluorides from the experimental values of the elastic constants and the lattice parameters of these compounds. The results indicate that the A-F bonds are quite central in character whereas the M-F bonds are axially symmetric; thus the short range A-F interactions are assumed to have the Born-Mayer form:ZZZZZBy studying the variations of the force constants with respect to the lattice parameter r, it is determined that ρ = 0·232 , λ = 2·8 × 10^?8 ergs for K⁺-F^?; ρ = 0·232 , λ = 4·1 × 10^?8 ergs for Rb⁺-F^?; λ₂, ρ₂ and ρ₂ are respectively 6·9 × 10^?10 ergs, 0·34 , 0·98for Co²⁺-F^? and 2·9 × 10^?10 ergs, 0·46 , 1·40for Mn²⁺-F^?. Taking into account both the short range repulsive potential and the long range electrostatic potential we can study the variations of the lattice energy as a function of r near the equilibrium position and deduce a theoretical value of the lattice distance. In spite of the simplicity of the model, the discrepancy between the experimental and the theoretical values is less than 10 per cent for all the compounds.     

Die Einwirkung der Te- und s-beimischungen auf die kristallisationskinetik des glasigen selens

The influence of tellurium (up to 6 at %) and sulphur (up to 2 at %) admixtures on the rate and on the activation energy E_Kr of vitreous selenium crystallization was investigated by means of calorimetric method. The results satisfy the Avrami's aquation x = 1 ?exp(?L · c_Kr · τ^z). The exponent z and the product z·E_Kr, are increased due to addition of tellurium admixtures, while the value L · c_Kr is decreased. The admixtures of sulphur decrease the exponent z, but have not any influence on the values L · c_Kr and z · E_Kr.Probably the tellurium admixtures increase the rate of the crystallite growth and the number of the crystallization centres, what accelerates the process. But at the same time, formation of the stable nucleus is prolonged. Sulphur admixtures do not change the contents of the small rings and of the hexagonal regions in vitreous selenium. They produce deffects in the chain structure, what retards the crystallization.     

Das gyromagnetische Verhältnis des 137 keV Rotationsniveaus von Os185

The rotation of the angular correlation of the 631 keV-137keVγ-γ-cascade in the decay of Re¹⁸⁶ in an external magnetic field of 53 500 gauß was determined to:ωτ=0·098 ± 0·008. The half life of the 137 keV level was measured as: T_1/2=(0·84 ± 0·03) · 10^?9 sec. The coincidences between the 137 keVγ-radiation and theβ-group of 927 keV maximum energy were used in connexion with a time to pulse height converter circuit. The coefficients of the angular correlation of the 631 keV-137 keV γ-γ-cascade were found as: A₂=? 0·073 ± 0·010; A₄=+ 0·310 ± 0·014. These values imply corrections for 3·9% admixture of internal bremsstrahlung and a 1 % contribution by K-X-radiation. The solid angle-corrections were done according to the formula given by E.Rose. The comparison with the theoretical coefficients for a (2⁺ 2⁺ 0⁺)-cascade shows that the multipolarity of the 631 keV radiation is pure E₂, the M₁ admixture being less than 0· 1%. This result is in agreement with the K-selection rule. There is no appreciable attenuation by internal fields. The comparison with the theoretical angular correlation gives for the integral attenuation factor: G₄=0·95±0·04; Assuming only attenuation by electric quadrupole interaction one gets for: G₂=0·92±0·07; The nuclear g-factor of the 137 keV rotational state was derived from these results without any further correction as: g_R= + 0·316±0·028.     

The (6Li, 6He) spin-isospin-flip reaction

A formulation of the (⁶Li, ⁶He) spin-isospin-flip scattering problem is presented. The method is applicable to quasielastic collisions between⁶Li described in pureLS coupling scheme and any target nucleus which can be described in a shell model or an adiabatic deformed-nucleus model picture. The effective interaction responsible for the (⁶Li, ⁶He) reaction involves an integration of the (σ₁ · σ₂) (ρ₁ · ρ₂) compo nent of the central part and the (τ₁· τ₂) tensor part of the nucleon-nucleon interaction over the internal wave function of the projectile. The ⁴⁸Ca(⁶Li,⁶He)⁴⁸Sc reaction populating the ($\text{πf}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{νf}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$) multiplet in ⁴⁸Sc is analysed. It that the tensor force makes some contribution to the transitions to high spin states.     

Radiative decay and autoionization in the4 D-states of the 3d 94s5s configuration in CuI

The CuI 3d ⁹4s5s ⁴ D-states, which lie above the ionization limit, were populated by stepwise collisional and laser excitation. With respect to their total angular momentum, the⁴ D-states have completely different decay modes. Whereas the lifetimesτ(⁴ D _7/2)=8.2(4)·10^?9s andτ(⁴ D _1/2)=7.9(6)·10^?9 s are determinrd by radiative transitions and were measured by time-resolved spectroscopy, the lifetimesτ(⁴ D _5/2)=1.59(6)·10^?12s andτ(⁴ D _3/2)=1.28(5)·10^?12s are due to autoionization and were deduced from the widths of the excitation signals observed by ion detection.