Transient fields for W ions traversing Fe hosts and for Os ions traversing Fe and Ni hosts

Transient field strengths were measured for^{184, 186}W ions traversing thin, magnetized Fe foils with velocities in the range 1.8 ≲ υ/υ₀ ≲ 5.7 (υ₀ = Bohr velocity) and for^{188, 190, 192}Os ions traversing polarized Ni hosts with average velocities 〈υ/υ₀〉 ∼ 4. The present measured transient field strengths, together with previously measured results for W, Os ions, are compared with transient field strength parametrizations, and discussed in terms of microscopic models of the transient field.     

Cross sections for single and double ionization of atomic helium under impact by fast multiply charged ions

Expressions for the cross sections for single and double ionization of atomic helium in collisions with fast multiply charged ions are obtained in the collision parameter range υ ²≫Z≳υ, υ ₀<c, where Z and υ are, respectively, the ion charge and ion velocity, υ ₀ is the characteristic velocity of electrons in the atomic helium ground state, and c is the velocity of light. Zh. Tekh. Fiz. 68, 1–7 (March 1998)     

Search for exotic contributions to atmospheric neutrino oscillations

The energy spectrum of neutrino-induced upward-going muons in MACRO has been analyzed in terms of effects of violating relativity principles, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of ν _μ → ν _τ transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter |Δυ| < 6 × 10⁻²⁴ at sin(2ϑ_υ) = 0 and |Δυ| < (2.5–5) × 10⁻²⁶ at sin(2ϑ_υ) = ±1. These limits can also be reinterpreted as upper bounds on the parameters describing violation of the equivalence principle. The text was submitted by the author in English.     

Low temperature cavity ring down spectroscopy with off-axis alignment: application to the A- and γ-bands of O2 in the visible at 90 K

The cavity ring down (CRD) technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of the cell can be changed between 77 K and 298 K. An off-axis alignment of the laser beam into the cavity is used to increase the number of resonant modes inside the cavity and improve the signal to noise ratio of the absorption bands. To demonstrate the capabilities of the low temperature CRD cell, the absorption spectra of O₂ are recorded at 90 K for the A (υ′=0←υ″=0) and γ (υ′=2←υ″=0) bands of the b¹?_g ⁺? X³?_g ^-b^{1}\sum_{g}^{ +}\leftarrow X^{3}\sum_{g}^{ -} transition using cavity ring down spectroscopy. The optical cavity performance was tested using two variations of the CRD technique. The A-band is measured using the phase-shift cavity ring down method and the γ-band using the pulsed-laser exponential-decay method. A comparison between experimental and simulated spectra of the O₂ bands at 90 K confirms the molecular temperature measured by a sensor localized in the cell. Quantitative measurements of the individual rotational line intensities are made for the oxygen γ-band to confirm the temperature of the cell and calculate the vibrational band intensity. The application of this technique for laboratory studies of planetary atmospheres and the spectroscopy of molecular complexes is emphasized.     

Investigation of the influence of incomplete fusion on complete fusion of <Superscript>12</Superscript>C-induced reactions at ≈ 4–7.2 MeV/nucleon

In this paper, we present the results of our investigation of reaction dynamics leading to incomplete fusion of heavy ions at moderate excitation energies, especially the influence of incomplete fusion on complete fusion of ¹²C -induced reactions at specific energies ≈ 4–7.2M eV/nucleon. Excitation functions of various reaction products populated via complete and/or incomplete fusions of a ¹²C projectile with ⁹³Nb, ⁵⁹Co and ⁵²Cr targets were measured at several specific energies ≈ 4–7.2 MeV/nucleon, using a recoil catcher technique, followed by off-line γ-ray spectrometry. The measured excitation functions were compared with theoretical values obtained using the PACE4 statistical model code. For representative non-α-emitting channels in the ¹²C + ⁹³Nb system, the experimentally measured excitation functions were, in general, found to be in good agreement with the theoretical predictions. However, for α-emitting channels in the ¹²C + ⁹³Nb, ¹²C + ⁵⁹Co, and ¹²C + ⁵²Cr systems, the measured excitation functions were higher than the predictions of the theoretical model code, which may be credited to incomplete fusion reactions at these energies. An attempt was made to estimate the incomplete fusion fraction for the present systems, which revealed that the fraction was sensitive to the projectile energy and mass asymmetry of the entrance channel.     

Studies with one- and two-proton drip line nuclei

In recent experiments at GANIL, we studied nuclei at the one- and two-proton drip line. The production rates allowed to search for direct 2p emission in the drip line nuclei ⁴²Cr, ⁴⁵Fe, and ⁴⁹Ni. No evidence for this decay mode was found in ⁴²Cr and ⁴⁹Ni, whereas the situation stays unclear for ⁴⁵Fe due to the limited statistics. In the medium-mass region ( A = 50-70), the half-life was measured for all proton-rich nuclei in the range T _z = 0 to T _z = - 1 between Z = 27 and Z = 36. First half-lives were determined for ⁶⁰Ga, ⁶²Ge, ⁶⁴As and ⁶⁶Se. Finally, β-decay studies of the 0⁺ → 0⁺ decay of ⁶²Ga have been performed at IGISOL in Jyv?skyl?. Non-analog transitions have been observed and are compared to theoretical predictions. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: blank@cenbg.in2p3.fr     

Conservation laws for classical and relativistic collisions. I

On the basis of simple kinematic arguments it is shown that any quantity, depending only on the nature and velocity of a particle, that is conserved in a collision must, in classical mechanics, be of the form λ+Σ_iμ_iυ_i+1/2vυ ² or in relativistic mechanics of the form λ+Σ_iμ_iυ_i[1−(υ ²/c ²)]^−1/2+νc [1−(υ ²/c ²)]^−1/2 where λ,μ _i, andν are particle parameters.     

High-spin states in 160Lu

High-spin states of ¹⁶⁰Lu have been studied through the ¹⁴⁴Sm( ¹⁹F, 3n) reaction. The previously known πh _11/2⊗υi _13/2 yrast band is extended from I ^π = 21^- to 25^- and a four quasiparticle band with configuration πh _11/2[523]7/2 ^-⊗υh _9/2[521]3/2 ^-⊗ (υi _13/2)² is reported. Received: 21 May 2001 / Accepted: 19 July 2001     

Defect-acceptor pairs in germanium

The PAC probe¹¹¹In was implanted into intrinsic, n-and p-doped germanium. After removing the radiation damage by thermal annealing the samples were irradiated with different lons to study defect-acceptor pairs by means of the PAC technique. In all samples a high electric field gradient could be observed, characterized by a quadrupole interaction frequency of υ_Q2=415MHz and an axial symmetry (η=0). Some samples show another frequency of υ_Q152.5 MHz and η=0. The results give evidence for an intrinsic defect trapped at the¹¹¹In probe.     

Effects of the interaction between R and Fe modes of the magnetic resonance in RFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> rare-earth iron borates

Resonance modes that are due to magnetic excitations in the exchange-coupled subsystems of rare-earth ions (R = Nd³⁺, Sm³⁺, and Gd³⁺) and Fe³⁺ ions have been detected in submillimeter transmission spectra (0.1–0.6 THz) of RFe₃(BO₃)₄ iron borate-multiferroic single crystals. The strong interaction between spin oscillations of the Fe and R subsystems has been revealed, which determines the behavior of the modes depending on the anisotropy of the exchange splitting of the ground doublet of the R ion. It has been shown that the intensities of coupled modes (contributions to the magnetic permeability) depend strongly on the difference between the g factors of Fe and R ions. This dependence makes it possible to determine the sign of the latter g factor. In particular, a noticeable intensity of exchange Nd modes in NdFe₃(BO₃)₄ is due to an increase in their contribution at g _{⊥, ‖}^Nd < 0, while in GdFe₃(BO₃)₄ with g _Gd ≈ g _Fe ≈ 2, the Fe and Gd contributions compensate each other and the exchange (Gd) mode is not observed. In spite of the weak interaction of Sm ions with the magnetic field, SmFe₃(BO₃)₄ exhibits resonance modes, which are attributed to the excitation of Sm ions through the Fe subsystem.     

Crystal structure and magnetic ordering of manganites La0.7Ca0.3Mn1 ? y Fe y O3

The influence of the replacement of Mn ions in the La_0.7Ca_0.3Mn_{1 − y} Fe _y O₃ compounds (0 ≤ y ≤ 0.09) by another transitional metal, Fe, was studied. The radii of both ions are almost identical, which makes the effect of the transitional metal on the physical properties of manganites more transparent. The crystal structure of three samples (with y = 0, 0.03, 0.09) is studied in the temperature range T = 1.5–300 K by neutron powder diffraction. All investigated samples belong to the orthorhombic space group Pnma (62). It is confirmed that Fe ions occupy the Mn positions in the unit cell. As the Fe concentration increases, the saturation value of the spontaneous magnetic moment and the Curie temperature decrease, but the ground state remains ferromagnetic for 0 ≤ y ≤ 0.1. The saturation values of the magnetic moments at T = 1.5 K are m _FM = 3.72(3), 3.40(3), and 3.27(3) μ _B /Mn for the samples with an Fe concentration y = 0, 0.03, and 0.09, respectively. Original Russian Text ? A.I. Kurbakov, V.S. Zakhvalinskii, R. Laiho, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 4, pp. 691–695.     

Conservation laws for classical and relativistic collisions. II

On the basis of elementary symmetry arguments it is shown that (1) if in classical mechanics there exists a quantity λ+Σ_iμ_iυ_i+1/2νυ ² that is conserved, where λ,μ _i, andν are particle parameters, then theμ _i andν are all proportional to a single parameterμ and the quantityAμ+Σ_iB_iμυ_i+C(λ+ 1/2Dμυ ²), whereD ≡ν/μ, is conserved for all values ofA, B _i, andC; (2) if in relativistic mechanics there exists a quantity λ+Σ_iμ_iυ_i[1−(υ ²/c ²)]^−1/2+νc[1−(υ ²/c ²)]^−1/2 that is conserved, then theμ _i andν are all proportional to a single parameterμ and the quantityAλ+Σ_iB_iμν_i[1−(υ ²/c ²)]^−1/2+Cμc [1−(υ ²/c ²)]^−1/2 is conserved for all values ofA, B _i, andC.     

Photocontrolled magnetic resonance plasticity of γ-irradiated KCl:Fe crystals

A photocontrolled resonance decrease in microhardness, which is due to the application of mutually perpendicular static and microwave fields, in γ-irradiated KCl:Fe crystals has been revealed. It has been found that the magnetic plasticity of unirradiated γ-KCl:Fe crystals is due to the resonance effect of magnetic fields on two types of impurity centers: first, centers containing Fe²⁺-ν _c ion-vacancy pairs and, second, centers containing Fe⁺ ions. The illumination of γ-KCl:Fe crystals with F-light (with a wavelength of λ = 500–600 nm) is accompanied by rearrangement of the spectrum of electron paramagnetic resonance detected by a change in microhardness. The effect of F-light on the spectrum of magnetic resonance plasticity is manifested as the suppression of the spectra of Fe²⁺-ν _c ions with effective g-factors of 7.0 and 3.5 due to their recombination with F-electrons and reconstruction to Fe⁺ centers with g-factors of 2.2 and 4.1.     

Magnetic coupling in Gd(Fe6−x Cr x )Al6: A57Fe Mössbauer study

⁵⁷Fe Mössbauer measurements have been made on the ternary ThMn₁₂-type intermetallic compounds Gd(Fe_6–x Cr _x )Al₆ withx=0, 0.5, 1.0, 1.5 and 2.0, at temperatures of 4.2 and 77 K. The principal effect of the Cr substitution is to reduce the⁵⁷Fe magnetic hyperfine field at 4.2 K in this series. The analysis of the⁵⁷Fe Mössbauer spectra is consistent with a ferromagnetic coupling between the Gd and Cr magnetic moments. These results are in agreement with previous studies by Felner et al. on GdCr₆Al₆, in which a ferromagnetic ordering withT _C=170 K was observed.On leave from Applied Acoustics Institute, Shaanxi Teachers University, Xian, PR China.     

The transient magnetic field for13C in iron

The time-integral transient-field precession has been measured for the first 5+/2 state in¹³C recoiling in magnetized iron at initial velocities ofv _i/v _o=3.4, 5.9, and 8.8. The results are consistent with recent findings for the extremely short-lived (=0.06 ps) 2 ₁ ⁺ state of¹²C. The transient magnetic field is found to exhibit a maximum of 4 MG at a velocity around 4v _o, supporting an interpretation originating in the polarization of halfempty s-shells of the recoiling carbon ions. Closed polycrystalline iron frames were used as ferromagnetic backings, and their properties as such are discussed.     

Overlapping B3Π0u ← X1Σ g/+ and 1Π1u ← X1Σ g/+ non-radiative characteristic of Br2 vapour in the wavelength region 505–541 nm

The vibronic vapour phase photoacoustic spectrum of Br₂ in the wavelength region 505–541 nm (19796–18480 cm⁻¹) has been recorded using microphone as well as pump-probe method. Discrete vibronic bands superimposed on a monotonically increasing continuum background towards the dissociation limit results from the overlapping B ³Π _0u ^/+ ← X ¹Σ _g ^/+ and ¹Π_1u ← X ¹Σ _g ^/+ electronic transitions. Vibronic bands originating from υ″=0 have been used to estimate the relative rate of non-radiative relaxation as a function of the excited state B ³Π_0u vibrational quantum number υ′. A comparison with the optical absorption spectroscopy of Br₂ leads to the identification of three broad spectral regions between 505 and 541 nm (19796 and 18480 cm⁻¹) on the basis of different non-radiative relaxation processes.     

Semiclassical asymptotics of the spectrum of a nonselfadjoint operator on the sphere

The asymptotics as ɛ → 0 of the spectrum of the shifted Laplace operator H = ɛΔ + ∂ _υ on the standard two-dimensional sphere is described, where υ is a vector field. Dedicated to the memory of Vladimir Borovikov