A finite element approach for the continuum spectrum of the Dirac radial equation

The Dirac radial functions are expanded in polynomial B-spline basis, transforming the Dirac equation in a generalized eigensystem matrix problem. Due to the locality nature of the B-spline functions the matrix representation of all the involved operators are highly sparse. Diagonalization of the matrix equations provides the bound and continuum eigenstates. Energies and oscillator strengths for Hydrogen and Rubidium are presented.AMS subject classification: 65705, 81V05     

Spectra of photons emitted from germinating seeds

Summary Photon emitted in the visible and near ultraviolet range by germinating soya seeds has been measured by means of a low-noise photomultiplier coupled to a data acquisition system. The photon energy spectrum, determined by means of a set of optical filters, shows two main contributions in the red and UV bands. Results show that both the radiation intensity and its spectrum change during germination according to seed physiological conditions. The photon emission of seeds at rest changes with their germinability. The UV component at the germination beginning is a factor 6 larger for living seeds than for the devitalized ones. This result can be interpreted as an experimental evidence of the existence of mitogenetic radiation. The authors of this paper have agreed to not receive the proofs for correction.     

Post-collision interaction effects on the triple-differential cross-section for the ionization of helium by fast positrons

Triple differential cross-sections for the ionization of helium by fast positrons are calculated in a ‘correlated’ first Born approximation supplemented by the inclusion of post-collision interaction effects. The results are analysed with respect to electron-helium experimental data of Jung and coworkers in coplanar asymmetric geometry.     

Comments on the capture cross-section of electrons in silver bromide grains

The values in the range of 10⁻¹⁵ cm² to 10⁻¹⁴ cm² have been reported by various authors for the capture cross-section of electrons at the traps in silver bromide grains. In this paper we have given a suitable value of this cross-section which is used for computing the track characteristics in nuclear emulsions (e.g. effective ionization, probability of development, grain density and mean gap length) and the ratio of the rate constant of recombination and trapping. Theoretical results agree well with the experimental observations and the available data of other workers and give a convincing support to our choice of this cross-section parameter.     

Excitation cross-sections of the4Do-levels of a cobalt atom under electron collision conditions

Cross-sections of the⁴D^o-levels of a cobalt atom are determined based on the results of measurements of 880 excitation cross-sections of the CoI spectral lines. Detailed calculations of branching and cascade population are made for the levels of the terms z⁴D^o, y⁴D^o, and x⁴D^o. Results of the present work and the cross sections calculated by R. K. Peterkop in the Born approximation are shown to be in good agreement. Moscow Power Engineering Institute, 14, Krasnokazarmennaya St., Moscow, E-250, 111250, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 561–565, September–October, 1997.     

Amplified spontaneous emission in neat films of arylene-vinylene polymers

Amplified spontaneous emission (travelling-wave lasing) was achieved for a set of 18 poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) related arylene-vinylene copolymers, a part of which substituted with additional phenyl groups at the vinyl double bond. Wave-guiding neat thin films on glass substrates were used. The samples were transversally pumped with single second harmonic pulses of a mode-locked ruby laser (wavelength 347.15 nm). Travelling-wave emission occurred in the wavelength region between 485 and 650 nm. Repeat unit based absorption cross-section spectra, normalized fluorescence quantum distributions, and amplified spontaneous emission spectra are presented. Ground-state absorption cross-sections at the wavelengths of peak amplified emission are extracted from effective gain length measurements. Effective stimulated emission cross-sections are derived from pump pulse energy densities necessary for optical narrowing.     

Experimental and theoretical study of line shift and mixing in the ν4 band of NH3 perturbed by N2

The shift coefficients and line-mixing parameters of rovibrational-inversion transitions in the ν₄ band of ammonia (NH₃) perturbed by nitrogen (N₂) have been measured at room temperature with a high-resolution Fourier transform spectrometer. The collisional shift and line mixing are obtained from the non-linear least-square multi-pressure fitting techniques. Comparison is made with the results of theoretical calculation based on semi-classical model extended to the case of symmetric top molecule with inversion motion. The shifts and the line-mixing parameters are calculated using, respectively the approach developed by Robert and Bonamy and the state-to-state cross-section. The agreement is satisfactory on the average. Good agreement is also obtained for line mixing with previous measurements.     

Relative Responses of Noble Gases Using a Pulsed Discharge Helium Photoionization Detector:Theoretical Calculation and Experimental Determination

The relative response factors（RRFs） for noble gas（Ng） were determined on a pulsed discharge helium photoionization detector. Using ab initio method, the atomic orbitals of noble gas were calculated and used to determine the number of ionizable electrons on the basis of the continuous emission of He2. The molar responses of noble gases is well correlated with the number of ionizable electrons.     

Analysis of microplastics and nanoplastics: How green are the methodologies used?

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纳秒脉冲下变压器油中闪络光信号特性

 对变压器油中闪络过程的光信号特性进行了分析。在预闪络阶段,光信号呈现出脉宽为2~4 ns,幅值为30~50 mV的不规则脉冲;临近闪络阶段,光信号频率更高,脉宽为1/2~1/3 ns,最高幅值也增长到约70 mV;在闪络阶段,光信号波形呈现出1个波峰或者2个波峰的形状,幅值差异显著。光信号的形状预示了闪络中流注通道的发展过程及流注通道中粒子的变化。分析表明：光电离是纳秒脉冲下变压器油中闪络的重要因素。