Beryllium diffusion across GaAs/(Al,Ga)As heterojunctions and GaAs/AlAs superlattices during MBE growth

Beryllium diffusion during MBE growth of (Al, Ga)As layers, (Al, Ga)As/GaAs heterojunctions and GaAs/AlAs superlattices has been studied by electrochemical C-V and secondary ion mass spectrometry (SIMS) concentration profiling, in conjunction with transmission electron microscopy. Diffusion times were comparatively short since they were limited to part of the growth sequence, so non-equilibrium effects had a significant influence. The results are consistent with an interstitial-substitutional mechanism in which lattice site incorporation becomes more difficult with increasing band gap enthalpy. Incorporation involves a kick-out reaction which leads to the observed disordering of the superlattices.     

Radiattonal capture of neutrons by deuterons n + d →3H + λ and P-odd nuclear forces

P-odd polarizational phenomena are considered in the radiative capture of neutrons by deuterons: n + d ³H + . It is shown that, in the general case, 18 different P-odd asymmetries of the angular distribution of quanta arise in the collision of arbitrarily polarized neutrons with a deuteron target characterized by vector and tensor polarizations. The P-odd contribution to the density matrix of the quanta formed in the capture of polarized neutrons by unpolarized deuterons is determined by eight real structural functions, while the P-odd dependence of the Stokes parameters of the photons on the tensor polarization of the deuterons is characterized, in the general case, by ten structural functions. In slow-neutron capture, the number of P-odd correlations is reduced.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 23–26, March, 1987.     

Estimating gas temperature in the channel of a high-temperature jet discharge in air

Consideration is made of determining gas temperature in the channel of a high-frequency jet discharge in air over the intensity distribution of lines for the rotational spectrum band for the transition A² X²II (0-0) in the radiation of hydroxyl. It is shown that the branches R₂ and Q₁ of this band are the most useful for temperature measurements at atmospheric pressure. Within error limits, the temperature in the discharge channel as determined from the lines of the R₂-branch is T_gas = (3120 ± 70) and (3380 ± 90) K in the cross sections of the discharge at a distance of 3 and 30 mm, respectively.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 3–7, February, 1987.     

Selecting the duration of excitation pulses for an electroluminescent thin-film matrix

The factors influencing the optimum selection of the excitation pulse width of thin-film electroluminescent devices is examined. It is shown that to excite an individual cell, a pulse width of 5–7 sec is sufficient, but to excite the matrix, the pulse width is determined by the independence of the conducting layer and the dimensions of the matrix. Formulas are cited for engineering calculations of the required pulse width.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 59–62, December, 1987.     

Self-activated luminescence of zinc sulfide

The nature of the luminescence of zinc sulfide in the spectral range (360), 380–420 nm (SAL) at 80K is analyzed. It is shown that the appearance of SAL radiation is accompanied by additional absorption in the region (350) 365–370 nm at 80K. The low-temperature spectra of sphalerite, exposed to different radiation and subjected to different treatment, are studied. The multiband luminescence of the isoelectronic sulfur impurity in ZnO deposits in the region 383–640 nm is discussed. It is concluded that SAL luminescence is attributable to the localization of excitons in ZnS on clusters, whose formation precedes the precipitation of the ZnO·S phase. The formation of oxygen clusters and deposits on dislocations in ZnS is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 60–66, February, 1987.     

Wirkungsgrade in der Welt des Lebens und der Technik

Zusammenfassung Um der oft gehörten Meinung entgegenzutreten, die energetischen Wirkungsgrade lebender Organismen seien wesentlich höher als die technischer Verfahren, werden entsprechende Werte miteinander verglichen. Der sehr niedrige Wirkungsgrad der Photosynthese zusammen mit der kleinen Energiedichte der Sonnenstrahlung erzwang ab einer kritischen Größe die Aufspaltung in Energiesammler, die Pflanzen, und Verbraucher chemischer Energie, den Tieren. Dank den 10 mal höheren Wirkungsgraden in der Technik, lassen sich Solarmobile bauen, die von der auf sie fallenden Sonnenstrahlung angetrieben werden. Wegen des Multiplikationsgesetzes der Teilwirkungsgrade ergeben sich sowohl für die Speicherung der Sonnenenergie in den fossilen Brennstoffen wie in der Nahrungskette extrem niedrige Wirkungsgrade.

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Efficiencies in the world of life and in engineering

One often hears the opinion, that the efficiencies in the world of life are higher than in engineering. To disprove this, many values of efficiency of corresponding processes are compared. The very low efficiency of photosynthesis in living plants together with the low density of solar radiation has led the world of life to split into collectors of energy, the plants, and consumers of chemical energy, the animals. Thanks to the ten times higher efficiencies of solar cells, it is possible, to produce solar mobiles, vehicles that move driven by solar radiation.

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Herrn Prof. Dr.-Ing. U. Grigull zum 75. Geburtstag gewidmet     

Using “quasiphotons” to compute wave fields in an elastic medium

Quasiphoton solutions are constructed for longitudinal and transversal waves in an elastic medium. The quasiphotons are then applied to determine the fields of nonstationary high-frequency point sources in a medium with parameters dependent on two Euclidean coordinates.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 148, pp. 89–103, 1985.     

Subbundles of maximal degree of the normal bundle of algebraic space curves almost complete intersection of special type

Summary LetX⊂P ³ be an irreducible smooth curve which is not a complete intersection. The main result of this paper shows that whenX is an a.c.i. of special type, i.e. its homogeneous ideal is generated by three polynomial of the same degreem, and additionallym>2, the subbundles of maximal degree of the normal bundle ofX inP ³ correspond to the singular points of maximal multiplicity of a plane curve which is the image ofX by a map (the linear system of the surfaces of minimal degree throughX). In particular this normal bundle is stable. The initial case of this family of curves, i.e. form=3, has been studied by E. Ballico-Ph. Ellia with different methods.

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Riassunto SiaX⊂P ³ una curva irriducibile e liscia che non è una completa intersezione. Il risultato principale di questa Nota mostra che quandoX è una almost completa intersezione di tipo speciale, cioè il suo ideale omogeneo è generato minimamente da 3 polinomi dello stesso gradom, e, inoltre,m>2, i sottofibrati di grado massimo del fibrato normale diX inP ³ corrispondono ai punti singolari di molteplicità massima di una curva piana che è l’immagine diX tramite una mappa (il sistema lineare delle superficie di grado minimo passanti perX). In particolare questo fibrato normale è stabile. Il caso iniziale di questa famiglia di curve, i.e. perm=3, è stato studiato da E. Ballico-Ph. Ellia con differenti metodi.

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This research is supported by GNSAGA (Italy).

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The main results of this paper have been the object of a talk at the meeting on ?Curves in Projective Space? held at Rocca di Papa in june 1985.     

Refinements of Yu. V. Prokhorov's theorems on the asymptotic behavior of the binomial distribution

One finds the asymptotic behavior of the minimax distance between the binomial and its approximating normal or Poisson distributions, taken with the second terms of their expansions.Translated from Veroyatnostnye Raspredeleniya i Matematicheskaya Statistika, pp. 4–19, 1986.     

Meson spectrum

Using the Klein-Gordon equation with a box potential, a mass formula describing the family of nonflavored meson states withI=1 is derived. The energy levels calculated agree with those observed within an accuracy of 5%. In the model discussed quarks behave like tachyons.