Phonon scattering by paraelastic defects

The relaxation timeτ(ω) for the scattering of the lattice waves of frequencyω by the paraelastic defects has been calculated by using the Feynman graph method, applied to a previous theoretical model [8]. A simple expression for the resonance component ofτ(ω)⁻¹ has been derived.

---

Zusammenfassung Die Relaxationszeitτ(ω) für die Streuung der Gitterwellen der Frequenzω an den paraelastischen Defekten wurde nach der Methode der Feynmanschen Graphen berechnet, wobei ein früheres theoretisches Modell [8] angewendet wurde. Ein einfacher Ausdruck für den Resonanzteil vonτ(ω)⁻¹ wurde hergeleitet.

---

Résumé Nous avons calculé le temps de relaxationτ(ω) des ondes du réseau de fréquenceω, qui sont diffusées par des défauts para-élastiques, en appliquant la méthode des graphes de Feynman à un modèle théorique antérieur [8]. Une simple expression pour la partie résonante deτ(ω)⁻¹ a été dérivée.

     

Note on the Hall effect in ice

The magnetic field dependence of the polarization correlation function is investigated. It is shown that the Hall effect is extremely small and probably inobservable because of the lattice anti-polarization produced by the motion of ionic defects and because of the incoherent motion of Bjerrum defects.     

Characterization of Gaseous Plasma Sustained in Mixtures of HMDSO and O2 in an Industrial-Scale Reactor

Optical emission spectroscopy and mass spectrometry was used to characterize gaseous plasma in an industrial reactor of volume 5 m³ during deposition of protective coatings. Plasma was created in mixtures of hexamethyldisiloxane (HMDSO) and oxygen at the powers between 1 and 8 kW. The plasma density was somehow below 10¹⁴ m^?3. The flows of both gases were varied up to 200 sccm while the effective pumping speed was adjusted by changing the roots pump rotation speed between 250 and 4000 rpm. At such conditions the HMDSO was only partially dissociated to fragments. The behaviour of optical emission lines and mass ion currents was well correlated indicating that even one single technique was sufficient to monitor the behaviour of plasma at various discharge conditions. The optical emission spectroscopy as a simple and economic method is therefore suitable for controlling key processing parameters in such a plasma reactor.

     

Green's function approach to paraelastic relaxation

The dynamical behavior of the elastic constants of a crystal containing paraelastic defects is investigated theoretically. A two-level model for the paraelastic defect is adopted, and the coupling between the defect and the lattice vibrations is considered to be strong. The imaginary part of the elastic compliance tensor is calculated by the Green's function method using the Feynman graph technique. It is shown that the change of the elastic compliance due to the defects is in general a superposition of the Debye-type relaxation and of resonant absorption of the acoustic waves. Expressions for the linewidth of the resonance and the Debye relaxation time are derived.     

Interaction of two-level tunneling system with phonons

Properties of two-level tunneling system which interacts with lattice vibrations are discussed in the framework of the polaron theory and the phase space approach. The decrease of the dynamic distortion of the lattice with increasing ratio η of the rigid-lattice tunneling matrix element to the small polaron binding energy is calculated in the intermediate coupling regime 0 < η < 2. A relatively sharp transition from the distorted to the undistorted state of the lattice takes place when η crosses the value 2. The expressions for the renormalized tunneling matrix element and for the longitudinal relaxation time T₁ are derived. A two-level tunneling model in which the double-well potential is asymmetric is also investigated.