Escape factors for laser-plasmas

A method of parameterizing escape factors (transmission factors and net radiative brackets) for conditions typical of laser-produced plasmas is introduced. The assumptions of planar geometry, exponentially decreasing emissivity and absorption coefficient with distance with a step rise at a particular point, and spatially constant Doppler broadened line profiles have been made. The effect of velocity gradients in spectrally shifting the absorption and emission line profiles relative to each other is taken into account assuming linear velocity gradients with distance. A parameter R representing the ratio of the spatial scale-length of the absorption coefficient to the Doppler decoupling length is introduced. Fitting formulae for transmission factors and net radiative brackets are given which are valid for all R and all optical depths. In the limit of small R (large Doppler decoupling length), the escape factors asymptotically approach formulae developed originally by, for example, Holstein assuming negligible plasma velocities. For large R (small Doppler decoupling length), the escape factors have been shown to asymptotically approach the Sobolev approximation. The parameterized net radiative bracket has been used in the hydrodynamic and atomic physics code ‘EHYBRID’ for the calculation of the effect of radiation trapping on population densities in laser-produced plasmas. The output of the modified EHYBRID code has then been post processed using the parameterised transmission factors to simulate 123 Ne-like and 399 F-like germanium resonance line intensities emitted in typical X-ray laser experiments. We obtain an agreement between the simulated and experimental spectra.     

The absorption spectrum of radiation-colored SrCl2-Ce crystals

We investigate the spectra of the x-ray radiation-induced absorption of SrCl₂−Ce crystals over the spectral range 345–830 nm and their temperature transformations in the interval from 77 to 450 K. We found that radiative color centers are characterized by a complex spectrum of induced absorption that contains wide bands of photochromic PC (750, 519, 378 nm) and PC⁺ (620, 446, 340 nm) centers and quasi-linear bands of Ce²⁺ centers. The most significant thermal transformations of radiative color centers occur in the vicinity of the thermostimulated luminescence peak of 394 K, at which the holes of the PC⁺ centers recombine with the electrons of the Ce²⁺ centers. Ivan Franko L’vov State University, 8, Kirilla i Mefodiya St., L’vov 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 545–547, July–August, 1997.     

On the spectrally resolved thermoluminescence of alumina

Summary The thermoluminescence of α-alumina was investigated by recording light emission simultaneouslyvs. temperature and wavelength. Samples were prepared, starting from amorphous alumina, by means of thermal treatments in the 850 to 1400°C temperature range. The recorded light exhibits two spectral bands at 553 and 706 nm emitted at temperatures close to 500 K, which reappear in the 700 K region with reduced intensity. The 553 nm band fades away in samples treated at temperatures exceeding 1200°C. The results are compared to a kinetic model which explains the most significant experimental features. Some qualitative arguments are advanced which could be useful in identifying the nature of the lattice defects responsible for the thermoluminescent emission observed.

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Riassunto Si è studiata la termoluminescenza dell'α-alumina registrando l'emissione di luce in funzione, simultaneamente, della temperatura e della lunghezza d'onda. Partendo da allumina amorfa, i campioni sono stati preparati mediante trattamenti termici nell'intervallo di temperatura da 850 a 1400°C. La luce registrata mostra due bande spettrali a 553 e 706 nm, emesse a temperature vicine a 500 K. Queste bande riappaiono nella regione attorno a 700 K con intensità ridotta. La banda a 553 nm svanisce nei campioni trattati a temperature al di sopra di 1200°C. I risultati sono paragonati ad un modello cinetico che spiega gli aspetti sperimentali più significativi. Vengono proposti alcuni argomenti qualitativi che potrebbero essere utili per identificare la natura dei difetti reticolari responsabili dell'emissione termoluminescente osservata.

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Резюме Исследуется термолюминесценция α-корунда, регистрируя интенсивность светового излучения в зависимости от температуры и длины волны. Образды изготавливаются из аморфного корунда, используя термическую обработку в области температур от 850°C до 1400°C. Термолюминесценция обнаруживает две спектральных зоны 553 и 606 нм, излучаемые при температурах, близких к 500 K, которые снова появляются в области 700 K с уменьшенной интенсивностью. Зона 553 нм затухает в образцах, обработанных при температуре выше 1200°C. Этот результат сравнивается с кинетической моделью, которая объясняет наиболее сушественные экспериментальные особенности. Приводятся некоторые качественные аргументы, которые могут быть полезны для идентификации природы дефектов решетки, ответственных за наблюдаемое термолюминесцентное излучение.

     

THREE-DIMENSIONAL NUMERICAL SIMULATION OF TROPICAL CYCLONE AND THE EFFECTS OF RADIATIVE PROCESSES ON IT

In this paper, a three-dimensional primitive equation numerical model includingvarious physical processes is constructed. Using this model, the development and thestructure of the tropical cyclone (typhoon) are first successfully simulated. Then theeffects of radiative processes on the development of the cyclone are investigated. Theradiative processes and their parameterization include long wave, short wave radiationand cloud type and cloudiness respectively. The results show that the tropical cyclonewill develop earlier and more quickly after the effect of radiative processes isincorporated, but the differences in intensity between the two cases with and withoutradiative processes at the final state are not evident. Only at the developing stage hasthe cyclone affected by radiation a sharper decrease in the surface pressure, a strongerwind and upward motion. a more obvious eye and eyewall, etc. All the results showthat the radiative processes are important in the earlier development stage of thetropica     

多肽净电荷数及等电点的计算

多肽净电荷数及等电点的计算许旭（中国药科大学药物分析教研室，南京，２１０００９）罗国安，林炳承（清华大学化学系）（中国科学院大连化学物理研究所）关键词毛细管区带电泳，多肽，净电荷数，等电点考察多肽在毛细管区带电泳（ＣＺＥ）中的迁移时，必须知道其在分析...     

Comment on ‘Topological Analysis of the Eigenvalues of the Adjacency Matrices in Graph Theory: A Difficulty with the Concept of Internal Connectivity’

Net signs of edge-signed graphs obtained for different choices of degenerate eigenvectors of an adjacency matrix are shown to become equal with a simple weighting procedure. However, in a few cases, this simple procedure is found to yield orderings of the eigenvectors based on the weighted net signs which are different from the orderings based on the eigenvalues.     

Absorption and emission spectra of isomeric tolunitriles

Absorption and emission characteristics ofo-, m- andp-tolunitriles in polar and non-polar solvents under different conditions have been investigated in detail. Solvatochromic shifts of band origin of these molecules in non-polar solvents show that their dipolemoments in the first excited singlet state are almost the same while its value in the second excited singlet is larger in the metathan in the para-isomer. Vibronic analyses of the low temperatures absorption, fluorescence and phosphorescence spectra of all the three molecules have provided evidence that these molecules are slightly distorted in the first excited singlet state while such distortion in the phosphorescence emitting triplet state is larger. The data on fluorescence and phosphorescence quantum yield and phosphorescence lifetime of the tolunitriles are reasonably interpreted as showing that in these molecules, particularly m-andp- tolunitriles, the internal conversion rate from the first excited singlet to the ground state is probably small and that the charge transfer character of the triplet state in thep-isomer is larger than that in the meta.     

INTENSITY CALCULATION IN STRONGLY ANISOTROPICALLY SCATTERING ATMOSPHERE WITH DISCRETE ORDINATE METHOD

The problems in some previous discrete ordinate method computations of radiative transfer are discussed, and a new manipulation is presented, which overcomes the difficulties in intensity calculations with the discrete ordinate method, and can be used to obtain accurate intensities with less streams. Even in strongly anisotropically scattering atmospheres the intensities in all directions including forward and backward directions of the direct radiation can be obtained satisfactorily.