Evaluation of the inelastic mean free path (IMFP) of electrons in polyaniline and polyacetylene samples obtained from elastic peak electron spectroscopy (EPES)

The inelastic mean free path (IMFP) of electrons was determined experimentally for selected polyaniline and polyacetylene samples with Ag and Ni references using elastic peak electron spectroscopy (EPES). The surface composition was determined by XPS and density by helium pycnometry. The high resolution hemispherical ESA-31 and ADES-400 spectrometers were used for measurements in the energy range E = 0.5–3.0 keV and E =0.4 − 1.6 keV, respectively. The integrated elastic peak intensity ratios for sample and reference were calculated using the Monte Carlo (MC) algorithm based on the electron elastic scattering cross-sections database NIST SRD64 version 3.1 and applying TPP-2M IMFPs for polymers. Surface excitation parameters (SEP) and material parameters ( _ach ) for polymers were determined, using the model of Chen, from comparison of measured and MC calculated elastic peak intensity ratios. These corrections proved to be efficient in decreasing the percentage deviations between the obtained IMFPs and the TPP-2M formula IMFPs. The elastic peak of hydrogen was observed in the EPES spectra of polymers. The experimental contribution of the hydrogen to the total elastic peak was 0.58%, while this value obtained from the MC simulations was 1.98%.      

Quadratic Integrals of Motion for Systems of Identical Particles: The Quantum Case

We consider the quantum dynamical systems of identical particles admitting an additional integral quadratic in momenta and find that an appropriate ordering procedure exists that allows converting the classical integrals into their quantum counterparts. We discuss the relation to the separation of variables in the Schrodinger equation. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 2, pp. 290–294, August, 2005.     

Partial inerting – A possible means of eliminating the brush-discharge-ignition hazard with explosive gases and vapours?

It was found that the brush discharge ignition hazard with IIA gases/vapours (propane) can be eliminated by reducing the oxygen/nitrogen volume ratio in the atmosphere to the order of 15/85. The condition is that the diameter of the earthed electrode ≤ 40 mm. Published information on whether an oxygen/nitrogen ratio of 15/85 is acceptable as regards the oxygen deficiency hazards is contradictory. With IIB gases/vapours (ethylene) the oxygen/nitrogen ratio must be reduced to at least 10/90 to eliminate the brush-discharge-ignition hazard. Lowering the oxygen/nitrogen ratio to this level will undoubtedly present a substantial oxygen deficiency hazard to humans.     

Irreducible Representations of an Algebra underlying Hidden Symmetries of a class of Quasi Exactly Solvable Systems of Equations

The set of linear, differential operators preserving the vector space of couples of polynomials of degrees n and n-2 in one real variable leads to an abstract associative graded algebra . The irreducible, finite dimensional representations of this algebra are classified into five infinite discrete sets and one exceptional case. Their matrix elements are given explicitly. The results are related to the theory of quasi exactly solvable equations. Received: 1 February 1996 / Accepted: 20 December 1996     

Numerical simulation of wall dynamics in (111)-oriented garnet films in the presence of an in-plane magnetic field

The domain wall motion in the presence of an in-plane magnetic field H_y perpendicular to the wall is simulated using a fall implicit numerical scheme. Calculations are performed for the drive fields 0 Oe<H_z<15 Oe and in-plane fields -210 Oe?H_y?210 Oe. The relation between the average wall velocity $\text{v}$ and the drive field H_z is discussed considering the wall structure. It was found that an in-plane field increases the peak velocity of the wall and extends the range of the drive fields, where the linear mobility relation is valid. A dynamical Bloch line stacking was found for sufficiently large drives. The influence of an in-plane field on the angular span of horizontal Bloch lines is discussed also. In particular the occurrence of 2π-horizontal Bloch lines is described. Numerical results obtained with a full implicit method are compared with the experimental observations of bubble motion and good agreement is found for |H_y|≤100 Oe.     

High-pressure transesterification of sterically hindered esters

A mild, rapid, and efficient method for the solvolysis of sterically hindered esters under high pressure is described. Transesterification is carried out in the presence of DBU at room temperature and at a pressure of 10 kbar to give quantitative conversions within short reaction times. The substrates examined included aromatic and aliphatic esters of sterically hindered alcohols and phenols. An optically pure benzyl ester of phenylalanine was chosen to study racemization of the amino acid esters under high-pressure reaction conditions.