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91.
92.
An exact analytic evaluation of the Kramers-Heisenberg matrix elements for Rayleigh scattering fromn=3 states of hydrogenlike atoms is performed in the nonrelativistic dipole approximation, using the Green's function method. The results are given separately for each subshell. The possibility of 3s?3d transitions is also considered. The dependence on the photon energy is contained in six invariant amplitudes. The formulas needed for the evaluation of the various cross sections are presented. The numerical results are contained in tables from which partial and total cross sections can be easily built, covering the energy range from zero up to 20 times theK threshold energy. In the vicinity of Balmerα frequency the cross section is large and comparable with that for excitedn=2 states, confirming an earlier hypothesis of Röhr. At other energies the cross sections forn=2 andn=3 states are comparable, too. The results should be useful in plasma diagnostics. 相似文献
93.
Internal conversion coefficients for inner shells of atomic ions of Sn are calculated for various degrees of ionization and compared with neutral atom predictions. The relativistic version of an analytic perturbation theory is used to include screening effects. 相似文献
94.
M. Boca V. Florescu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):15-20
We define 1D Volkov states as solutions of the one-dimensional Dirac equation in a time dependent electric field, similar
to the Volkov solutions in the three dimensional case. They are eigenspinors of the momentum operator and reduce in the absence
of the field to free solutions of positive or negative energy. Then we add a time independent attractive Gausssian potential
and, by integrating the Dirac equation for a laser pulse of Gaussian shape,
we determine the state which coincides initially with the ground state of the system in the absence of the electric field.
Our main objective is the study of the population dynamics on the Volkov states during the pulse action. For different values
of the laser pulse intensity and two values of the potential depth, we find that the Volkov states which
evolve from free solutions of negative energy are practically not populated, in contrast to the
population on free negative energy states. 相似文献
95.
Yan Liu Viorica Lopez-Avila Marcela Alcaraz Werner F. Beckert 《Journal of separation science》1993,16(2):106-112
The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n-pentylmagnesium bromide prior to gas chromatographic analysis). A 23 factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride. 相似文献
96.
97.
Viorica Lopez-Avila 《Journal of separation science》1980,3(11):545-550
Combination of various GC detectors by using a Varian effluent splitter with glass capillary columns has been found to be a rapid procedure for profiling organics extracted from sludges and river sediments. The selectivity and the increased sensitivity of the thermionic nitrogen-phosphorus detector (TSD), the electron capture detector (ECD), and the flame photometric detector (FPD) over the flame ionization detectors (FID) or mass spectrometers allow the detection of compounds present at trace levels without need for extensive sample cleanup. Furthermore, the combination of two selective detectors may supplement the information with regard to the chemical functionalities required for structure elucidation. 相似文献
98.
Adriana Popa Lavinia Macarie Ecaterina S. Dragan Viorica Parvulescu Gheorghe Ilia 《International Journal of Polymer Analysis and Characterization》2020,25(6):457-466
Abstract The chlorometylated styrene–divinylbenzene copolymer with different percent of divinylbenzene (code: S-6.7 DVB, S-12DVB, and S-15DVB) was functionalized with 3-hydroxybenzaldehyde for obtaining intermediated polymers. The aminotrimethoxysilanphosphonate groups were grafted by one-pot reactions in tetrahydrofuran using three components: polymers grafted with aldehyde groups (code: CHO-6.7, CHO-12, and CHO-15), 3-aminopropyltrimethoxysilane, diethylphosphite. The aminotrimethoxysilanphosphonate groups functionalized onto styrene-(6.7, 12, and 15%) divinylbenzene copolymer (code: PAF-6.7, PAF-12, and PAF-15) and evolution of the reaction were evidenced by FT-IR spectroscopy and porous structure by N2 adsorption-desorption, SEM microscopy. The thermal behavior of aldehydes and materials: PAF-6.7, PAF-12, and PAF-15 are different than initial polymer supports. 相似文献
99.
In the present work, kinetics of tartrazine decay by UV irradiation and H2O2 photolysis, and the removal of total organic carbon (TOC) under specific experimental conditions was explored. Irradiation experiments were carried out using a photoreactor of original design with a low-pressure Hg vapour lamp. The photodegradation rate of tartrazine was optimised with respect to the H2O2 concentration and temperature for the constant dye concentration of 1.035 × 10?5 M. Tartrazine degradation and the removal of TOC followed the pseudo-first-order kinetics. The much higher k obs value for tartrazine degradation (7.91 × 10?4 s?1) as compared with the TOC removal (2.3 × 10?4 s?1) confirmed the presence of reaction intermediates in the solution. 相似文献
100.