Nonlinear Raman scattering of photons by a channeled particle

Channeled particles are characterized by the discrete spectrum of bound transverse motion. The interaction of photons with channeled particles in single crystals can be accompanied by energy transitions between the levels of transverse motion of the channeled particle. The Raman scattering of photons at a quasibound channeled particle leads to the appearance of a combination of frequencies: the incident radiation frequency ω₀ and the frequency Δω_{m, n}, i.e., ω = ω₀ ± Δω_m,n where Δω_m,n = 2Δε_m,nγ²; Δε_{m, n} is the energy of the transition between quantum states (m and n) of the transverse motion of the channeled particle; and γ = E/mc² is the Lorentz factor of the channeled particle. The appearance of a violet satellite (the anti-Stokes component) in the Raman scattering spectrum is analyzed. The three-photon Raman-type transition, which is the process of the simultaneous absorption of two photons with the frequency ω₀ with the emission of a photon with the frequency ωs = 2ω₀ ± 2Δε_m,nγ², is considered. The conditions for resonance observation during the formation of the second harmonic (ω = 2ω₀) are discussed.     

磁畴壁在复合外场中的运动方程及其在磁弹性内耗的应用

在以速率α匀速增加的磁化场中,测量铁磁性材料的内耗时,材料中畴壁所受的力除了外加磁化场所提供的主驱动力A₀⁰+A₁⁰αt,以及测量内耗所用交变应力所提供的微扰交变驱动力A₃⁰sinωt之外,经分析表明,还存在一项在数值上与主驱动力及交变驱动力的乘积成正比的交互作用驱动力,可写为A₂⁰sinωt。这里的A₀关键词：     

Feldgleichungen der TREDERschen Gravitationstheorie,die aus einem Variationsprinzip ableitbar sind. I

In the frame work of TREDER 's gravitational theory we consider two classes of field equations which are derivable from two classes of LAGRANGE ian densities Ω⁽¹⁾(ω₁, ω₂), Ω⁽²⁾(s?₁, s?₂). ω₁, ω₂; s?₁, s?₂ are parameters. Ω⁽²⁾(ω₁, ω₂) gives us field equations which are up to the post-NEWTON ian approximation in the sense of NORDTVEDT , THORNE and WILL equivalent to the field equations given by BRANS and DICKE . For ω₂ = ?1 ?2ω₁ field equations follow from Ω⁽¹⁾(ω₁, ?1 ?2ω₁) which are in the above mentioned sense of post-NEWTON ian approximation equivalent to EINSTEIN 's equations. The field equations following from Ω⁽¹⁾(ω₁, ω₂) have a cosmological model with the well known cosmological singularities for T → ± ∞ in case that ω₁/(1 +3ω₁ +ω₂) ? γ > 0. For ω₁/(1 +3ω₁ +ω₂) ≤ 0 cosmological models with no cosmological singularities exist. From Ω⁽²⁾(s?₁, s?₂) we obtain field equations which at the best give us perihelion rotation 7% above EINSTEIN 's value and light deflection 7% below the corresponding EINSTEIN 's value. But in that case we are able to show the existence of a cosmological model without any cosmological singularity.     

Singlet—triplet oscillations of spin-correlated radical pairs due to the Larmor precession in low magnetic fields

Singlet—triplet oscillations in spin-correlated radical pairs have been studied at magnetic field strengths low for one radical and high for the other. Oscillations with frequencies close to the Larmor frequency ω₀ of electron spin precession have been predicted under these conditions. Both numerical and exact analytical solutions in arbitrary magnetic fields are presented for three cases of hyperfine couplings in wide-spectrum radical. For the case of unresolved spectrum, singlet—triplet evolution was found to contain a single oscillating term with frequency ω₀. In the case of one spin-I magnetic nucleus, there are two low frequency oscillating terms with frequencies ω_? = ω₀ ? ω₀/(2I + 1) and ω₊ = ω₀ + ω₀/(2I + 1), the amplitude of the first term being larger than that of the second. The case of a number of equivalent protons also has been analysed as a superposition of one-nucleus oscillations. The predicted oscillations were observed in a time resolved magnetic field effect for several radical ion pairs produced by X-ray irradiation of alkane solutions with charge acceptors. For pairs (p-terphenyl-d ₁₄)^?./(isooctane)^+. and (p-terphenyl-d ₁₄)^?./(2,4-dimethylpentane)^+. the oscillation frequency in a field B ₀ of 0.5–4mT is about 20% lower than ω₀. Oscillations were observed also in pairs with equivalent nuclei: (p-terphenyl-d ₁₄)^+./(C₆F₆)^?. and (p-terphenyl-d ₁₄)^?./(hexamethylethane)^+.     

On the low-temperature thermal conductivity of Ni-doped Al2O3

An attempt is made to explain the lower resonance anomaly in the thermal conductivity of Ni-doped Al₂O₃ by using τ_r ～ ω^-4s(ω² ? ω²_r)². An agreement between theory and experiment needs s = 0.71, and this is interpreted to mean that the frequency dependence of impurity-phonon coupling is approximately described by ω^0.71 for phonons having frequencies in close neighbourhood of ω_r.     

Antiferromagnetic Resonance in GdB<Subscript>6</Subscript>

The electron spin resonance has been measured for the first time both in the paramagnetic phase of the metallic GdB₆ antiferromagnet (T_N = 15.5K) and in the antiferromagnetic state (T < T_N). In the paramagnetic phase below T* ~ 70 K, the material is found to exhibit a pronounced increase in the resonance linewidth and a shift in the g-factor, which is proportional to the linewidth Δg(T) ~ ΔH(T). Such behavior is not characteristic of antiferromagnetic metals and seems to be due to the effects related to displacements of Gd³⁺ ions from the centrosymmetric positions in the boron cage. The transition to the antiferromagnetic phase is accompanied by an abrupt change in the position of resonance (from μ₀H₀ ≈ 1.9 T to μ₀H₀ ≈ 3.9 T at ν = 60 GHz), after which a smooth evolution of the spectrum occurs, resulting eventually in the formation of the spectrum consisting of four resonance lines. The magnetic field dependence of the frequency of the resonant modes ω₀(H₀) obtained in the range of 28–69 GHz is well interpreted within the model of ESR in an antiferromagnet with the easy anisotropy axis ω/γ = (H ₀ ² +2H_AH_E)^1/2, where H_E is the exchange field and H_A is the anisotropy field. This provides an estimate for the anisotropy field, H_A ≈ 800 Oe. This value can result from the dipole?dipole interaction related to the mutual displacement of Gd³⁺ ions, which occurs at the antiferromagnetic transition.     

Nuclear orientation and NMR/ON on implanted114mIn in Fe and Co

Nuclear orientation and NMR/ON of^114mIn implanted into Fe at an energy of 80 keV and dose of 3–5×10¹⁴ cm^–2 is reported. The zero applied field resonance frequencyv ₀=203.65(6) MHz is combined with the recently determinedB _hf(InFe) of 286.8(3) kG to yield (^114mIn)=+4.658(14) nm. The nuclear spin-lattice relaxation time for^114mIn in iron is measured to be 88(18) s at 18 mK and the applied field dependence of the NMR/ON resonance frequency gives the Knight shift for the system as –2.4(6)%. The absence of measurable nuclear orientation in similarly prepared^114mInCo sources is discussed.     

关于等离子体中的瞬变过程

利用Spitzer的广义欧姆定律分析等离子体中由垂直于磁场的压强梯度所引起的宏观瞬变性质。在垂直于磁场方向的初始流动速度为零的条件下,得出在恒稳磁场中的瞬时扩散系数(当ω_ceτ?1)为 D= (2km_ec²)/e² T/(B²τ)+(kc)/eT/Be^-m_e/(miτ)tsinω_cit,式中τ为电子离子的平均碰撞时间间隔。     

Parametric Excitation of Plasma instabilities by two Monochromatic Pump waves

The dispersion characteristics of a plasma in a pump field ??(t) = ?? sub ω₀t + ??₁ sin ω₁t are considered. Firstly we assume, that the second wave is weak (|??₁| ? |??₀|) and the frequency ω₁ is near sω₀(ω₁ = sω₀ + Ω,Ω ? ω₀). We obtain the dispersion equation, describing the parametric coupling of the waves driven by the strong field ??₀ sin ω₀t under the resonance condition ω₀ ≈ ω_Le/P and derive the expressions for the growth rates (ω_Le is the electron LANGMUIR frequency; s, p are integers). In the second part it is shown, that a strong field ??₁ with a frequency ω₁ much larger than ω _Le(ω _Le ≈ pω₀) stabilizes the plasma; the growth rates are reduced and the frequency region of the parametric instability is contracted.     

Resonances of orientation and alignment of atoms in the case of inclined optical pumping

It is shown that, with pumping inclined relative to a constant magnetic field H₀, the radio-frequency (RF) magnetic field rotating at frequency Ω induces new resonances ω₀ = γ H ₀ and 2Ω for the Fourier components of orientation and ω₀ = ?Ω, Ω/2, 3Ω/2, 2Ω, and 3Ω for the components of alignment. New resonances excited by the oscillating RF field are also considered.     

Stimulated Raman spectra of a strong bichromatic field interacting with a three-level atom

We have studied the stimulated Raman spectra arising from the interaction of a three-level atom with two strong electromagnetic fields whose initially populated modes ω _a and ω _b are in resonance with the two atomic transition frequencies. The Green's function formalism has been used in the limit of high photon densities to calculate the excitation spectra near the frequencies ω = ± ω _ab = ± (ω _a - ω _b ). Expressions are derived for the relative intensities, which describe, apart from the usual Raman peak at the frequency ω = ω _ab , four pairs of lorentzian lines peaked at the frequencies ω - ω _ab = ± Ω _a /√2, ± Ω _b /√2, ± Ω and ± 2Ω, respectively, and having spectra widths of the order of 3γ₀/4. The parameter Ω is defined as Ω² = (Ω _a ² + Ω _b ²)/2, where Ω _a and Ω _b are the Rabi frequencies of the two laser fields and γ₀ is the spontaneous emission probability. Numerical calculations for selected values of the Rabi frequencies are graphically presented and discussed. Conditions have been established for which Raman gain processes are anticipated to take place.     

Double resonance interference in third-order light mixing

The first observation of interference effects between two sharp resonant contributions to the third-order nonlinear susceptibility χ₍₃₎ (ω₃=ω₀+ω₁?ω₂) is reported. Using two tunable near ir frequencies, ω₀=ω₁ and ω₂, the was seen in crystalline CuCl when 2ω₁ and ω₁?ω₂ were close to the sharp Z₃ exciton at 3.21 eV and the 210 cm^-1 Raman line, respectively. Three different tunable visible frequencies were used to observe similar interference effects in a benzene-cyclohexane mixture when ω₀?ω₂ and ω₁?ω₂ were close to the 992 cm^-1 Raman line of benzene and the 801 cm^-1 Raman line of cyclohexane, respectively.     

[Russian Text Ignored]

The parametric excitation of longitudinal waves in an infinite homogeneous plasma by a pump field E (t) = E ₀(t) sin (ω₀t + φ(t)) is studied on the basis of the Vlasov equation, where the amplitude E ₀(t) and the phase φ(t) are slowly varying compared with ω₀ periodic functions. Firstly it is assumed that ω₀ is much larger than the electron plasma frequency ω_Le. In the second part the parametric instabilities are considered under the resonance condition ω₀ ≈ ω_Le. In both parts the threshold fields for the excitation of the longitudinal waves and their growth rates are calculated. As an example these values are analysed for both a sequence of pump impulses and a phase-moduated pump field. They are compared with the results received for a monochromatic pump field.     

Cyclotron resonance of polarons in AgBr at high microwave fields

A cyclotron resonance experiment on polarons in pure AgBr has been extended to the microwave field of 3 kV cm^?1 by using a pulsed magnetron at 35 GHz at lattice temperatures of 4.2 and 17 K in magnetic fields up to 58 kOe. It was established that the ground state polaron mass is m¹_p(0)=(0.287±0.003)m_e. From microwave field dependences of the peak position and the width of resonance lines, it was established that the electron polaron follows the streaming motion repetitively emitting LO-phonons in the microwave field region above 80 V cm^?1. Further, it was also suggested that, when streaming, the polaron has an enhanced effective mass of (0.353±0.006)m_e rather than the ground state mass m¹_p(0).     

Natural electron oscillations in granular indium films deposited on rough surfaces of NaCl and KCl single crystals

Two plasma resonance bands were simultaneously observed in granular indium films deposited on rough surfaces of NaCl and KCl single crystals; one of them is caused by a combined action of the light-wave field and of the field created by the dipole grains, and the other, by the light-wave field alone with the frequency of natural electron oscillations ω₀ in the grains. The indium plasma frequency, calculated from the measured frequencies ω₀ and known dielectric constants of NaCl and KCl, agrees well with the known plasma frequency of bulk indium. An anisotropy in the plasma resonance band of granular indium films deposited on a rough NaCl surface was found and interpreted.     

Nonlinear susceptibility x;(3) in a direct gap semiconductor derived from coupled inter-and intraband equations of motion

A set of generalized Maxwell Bloch Equations describing a two band semiconductor as a system of interacting two level atoms is used to calculate the nonlinear dielectric susceptibility x;⁽³⁾ (ω, ? ω, ω). For near resonance conditions (ω ≈ ω_g) we find a simplified expression for χ⁽³⁾ that is compared with other theories. A fit using parameters relevant for InSb leads to good agreement with experimental results.     

Resonant destabilization of phonon microwave stimulated emission in an acoustic quantum oscillator (phaser) with periodically modulated pumping

Two qualitatively different types of resonant destabilization of phonon stimulated emission (SE) are discovered in experiments where a 9-GHz multimode ruby laser is periodically modulated (the electromagnetic pump frequency is 23 GHz). In the case of deep pump modulation at low modulation frequencies (ω=70–200 Hz, where ω_m is the modulation frequency), a fast random alternation of microwave phonon SE modes is observed. This destabilization range corresponds to relaxation resonance in optical lasers. Outside the relaxation resonance range (at ω_m≈10 Hz), the other type of resonant destabilization of stationary phonon SE is observed. This destabilization shows up as very slow regular self-detunings of the microwave SE spectra. The period of such self-organized motions depends significantly on ω_m and changes by several orders of magnitude when ω_m varies within several percent. The second type of SE resonant destabilization is explained in terms of antiphase energy exchange between modes in a modulated phaser.     

Precise determination of the ground state hyperfine splitting of135Ba+

A microwave-optical double resonance experiment has been performed on¹³⁵Ba⁺ ions, confined in a r.f. quadrupole trap. Linewidths as narrow as 0.9 Hz have been obtained on the 7.18 GHz,F=1,m=0 toF=2,m=0 transition. Shifts of the resonance frequency due to magnetic stray fields and the electric trapping field have been observed. The final result, extrapolated to zero field strengths, isΔ υ _HFS=7183340234.90(0.57) Hz.     

Anticrossing phenomena in a resonator with 2D electrons on liquid helium

We have investigated the details of the eigenmode for a resonator containing a two-dimensional electron system (2DES) formed on the surface of liquid helium. We show that anticrossing phenomena occur near the crossing point ω₀=ω_c, where ω₀ is the eigenmode of the resonator and ω_c is the cyclotron frequency. The structure of the coupling constant is established. It is a flexible parameter, i.e., sensitive especially to magnetic field and electron density. A finite coupling leads to a perturbation, δω, of the eigenmode of the resonator in presence of the 2DES. Corresponding calculations and measurements of δω are presented. The theory fits the experimental data. The influence of anticrossing on the cyclotron resonance absorption line shape is demonstrated.     

Nuclear magnetic resonance in ferromagnetic HCP and FCC 59cobalt

The ⁵⁹Co nuclear magnetic resonance spectra of powdered metal have been investigated in the temperature range from 3 K – 295 K. Both HCP resonance lines, coming from nuclei at the center and the edge of the domain walls (v₁ = 221 MHzv₂ = 214 MHz at 295 K, respectively) have been observed as in bulk material. The quadrupole splitting, directly measured only by Kawakami et al., was verified. The line spacing v_q = 3e²Qq/2I(2I - 1)h is v_q = (178 ± 5) kHz at 295 K. A new line with v = 221.7 MHz at 295 K was found, which is probably due to a stacking fault.The temperature behaviour of the FCC-linewidth is anomalous. Between 3 and 10 K a line splitting due to frequency pulling, already predicted by De Gennes et al. in 1962, was discovered. The frequency shift derived from the splitting of the FCC line at 3 K is δω₀ ≈ 2.51 MHz. The corresponding anisotropy field and zero field ferromagnetic resonance frequency of FCC cobalt are H_A ≈ 1.25 × 10² Oe and ω_e ≈ 2.27 × 10⁹ Hz, respectively.