Energy levels, wavelengths, transition rates and line strengths are reported for the 2s^22p^3-2s2p^{4} transition array in Kr(XXX), Rb(XXXI) and Sr(XXXII). Wave functions were determined using the multiconfiguration Dirac-Fock method with account for valence and core-valence correlation effects. The present results are presented and compared with experimental data and with values from other calculations. The calculated values including core-valence correlation are in good agreement with other available theoretical and experimental values, and therefore can be used for the further astrophysical investigations.
The high resolution spectroscopy of nanometric alkali-vapor layers has been made possible through the development of extremely thin cell. We present a detailed comparison of the fluorescence profiles amplitude and width, obtained in the extremely thin cell, both theoretically and experimentally. Experiments are performed on the D_{2} line of Cs-vapor layer with thickness L = mλ, where m = 0.5, 0.75, 1, 1.25. The enhancement rate of the transition profiles width is not growing monotonously, but it is larger for L varying in the interval from L = 0.75 λ to L = λ than that varying in the interval from L = λ to L = 1.25 λ. The used theoretical model, based on the optical Bloch equations is in qualitative agreement with the experimental observations.
The high resolution spectroscopy of nanometric-thin alkali-vapor layers was made possible through the development of extremely thin cell. We have investigated the behavior of the extremely thin cell fluorescence spectra both experimentally and theoretically. Experiment is performed on the D_2 line of Cs-vapor-layer with thickness L=mλ, where m = 0.5, 0.75, 1, 1.25. For open optical transitions, the fluorescence spectra shows narrow dip on the top of the sub-Doppler-width fluorescence profile, at L≥λ. In case of closed transition, an extremely small feature in the fluorescence slightly shifted from its maximum is observed at L =(5/4)λ. The used theoretical model, based on the optical Bloch equations is in qualitative agreement with the experimental observations.
We present the first experimental observation of narrow dips in the fluorescence profiles of completely closed hyperfine transitions in Rb vapor at high atomic density, which is attributed to the depolarization of the excited state. Moreover, at low atomic density, a narrow peak on the top of the fluorescence profile is demonstrated, centered at the completely closed transition within the D_{2} line of Cs. Experiments are performed in thin (700 μm) alkali cell by single light beam spectroscopy. The cell is filled with Cs containing a small portion of Rb.
Alloying effect on the K_{α} and K_{β} X-ray fluorescence cross-sections in Cr_{x}Ni_{1-x} and Cr_{x}Al_{1-x} alloys was studied. The samples were excited by gamma rays with energy 59.5 keV from a^{241}Am radioisotope source and K X-rays emitted by the samples were counted with a Si(Li) detector. We found that K_{α} and K_{β} X-ray fluorescence cross-sections are changed by alloying effect in Cr_{x}Ni_{1-x} and Cr_{x}Al_{1-x} alloys for different composition x. We compared our results with the theoretical values.
Recently experimentally determined individual (fine structure) line strengths for the spectra of NI, FI, and NeII are analysed, searching for regularities resulting from similarities in the structure of these species. Strengths of spectral lines of the prominent 3s-3p and 3p-3d transition arrays are investigated. The absolute scales of these experimentally derived data are based on independently determined lifetimes for excited levels of NI, FI, and NeII. The simple Coulomb approximation method was applied for calculations of the matrix elements for the "jumping" electron in order to obtain an average trend in line strengths of the studied emitters. In the case of the isoelectronic species (FI, NeII), additionally the trend resulting from the perturbation theory is taken for comparison. Except the trend study of the absolute scale, the strengths of individual lines within analogous multiplets (in a relative scale) are investigated and compared with data resulting from LS coupling scheme and with semi-empirical calculations.
Energies and transitions for allowed (E1) and forbidden (E2, M1, and M2) lines for low-lying configurations in magnesium-like tungsten (W^{62+}) are studied using the multiconfiguration Dirac-Hartree-Fock approach. It is shown that the correlations within the n=3 complex, quantum electrodynamic and Breit effects are very important for the calculation of fine structure energies. The present results are compared to and agree very well with other theoretical energies, wavelengths, transition probabilities and line strengths previously published for a few lines, and are generally found to be more reliable than previous theoretical predictions. The data for E2, M1, and M2 for transitions between the levels are presented as supplemental material. Results are also compared with other theory, when available.
A critical analysis of available experimental and theoretical data on transition probabilities for spectral lines of singly ionized nitrogen was performed. J-file sum rule tests for the 3s-3p triplet supermultiplet in NII were performed on the basis of recently calculated and measured line strengths. It is shown that the inclusion of intersystem transitions in the analysis leads to a better agreement of the data with the J-file sum rule prediction.
The 4S' [1/2]0 → 4P' [3/2]1 transition of Ar(I) in a facing target sputtering chamber is measured using a Ti:sapphire ring laser at several operating conditions. Doppler width and line intensity are determined by analysis using the Voigt function. The thermodynamic temperature determined from the Doppler width increases linearly with discharge current and gas pressure. The population density from the line intensity is reduced to the reference temperature obtained by interpolating the discharge current to zero. The empirical relationship to describe population density at a discharge current and a gas pressure is discussed.
The geometries, electronic structures, polarizabilities, and hyperpolarizabilities of organic dye sensitizers 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile were studied based on density functional theory using the hybrid functional B3LYP. Ultraviolet-visible spectra were investigated by time dependent density functional theory. The features of electronic absorption spectra in the visible and near-UV regions were assigned based on time dependent density functional theory calculations. The absorption bands are assigned to π → π* transitions. Calculated results suggest that the three lowest energy excited states of 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile are due to photoinduced electron transfer processes. The interfacial electron transfer between semiconductor TiO_2 electrode and dye sensitizers 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile is due to an electron injection process from excited dyes to the semiconductor's conduction band. The role of amide and methyl groups in phthalonitrile in geometries, electronic structures, and spectral properties were analyzed in a comparative study of 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile for the improvement of dye sensitized solar cells.
L X-ray fluorescence cross-sections of some elements in the atomic number range 50 ≤ Z ≤ 59 have been calculated theoretically according to subshell excitation energies of elements. The Coster-Kronig transitions (f₁₂, f₂₃, and f₁₃) are non-radiative transitions. The Coster-Kronig enhancement factors due to the effect of the Coster-Kronig transitions on L X-ray fluorescence cross-sections have been calculated theoretically. The calculated values have been compared with other earlier experimental and theoretical values.
In this study, K_{β}/K_{α} X-ray intensity ratios of zinc in pure zinc, undoped ZnO thin film and boron and fluorine-doped ZnO thin films have been investigated. These samples have been excited by 59.5 keV γ-rays from a ^{241}Am annular radioactive source. K X-rays emitted by the samples have been counted using an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The K_{β}/K_{α} X-ray intensity ratios of the doped ZnO thin films have been compared with that of the undoped ZnO thin film. The deviations between the results can be explained by delocalization and/or charge transfer phenomena causing change in valence electronic configuration of zinc.
Population densities of excited CI and CII levels are calculated in helium and argon plasmas containing small admixtures of CO_{2}. Calculations are performed for a total pressure of 1 atmosphere, in a temperature interval from 8000 K to 40000 K, assuming local thermal equilibrium (LTE) and partial local thermal equilibrium (pLTE) conditions. Normal temperatures are obtained for selected excited CI and CII levels. The results are applied to a helium plasma with traces of CO_{2}, of cylindrical symmetry with presumed radial temperature distribution. Effective intensities of CI and CII spectral lines, corresponding to side-on radiance measurements along the cylinder diameter are evaluated. On hand of these effective line intensities and applying the Boltzmann plot method effective temperatures are evaluated and compared with the presumed temperature distribution.
Exciplex and excimer formation have been probed in several jet cooled complexes using mass selective two-photon ionisation and fluorescence excitation spectroscopy as well as ground state depletion spectroscopy (hole burning): (i) In the anthracene-dimethyl-ortho-toluidine system, it has been found that the ionisation step takes place with a much higher efficiency from the charge transfer state responsible for the exciplex emission than from the locally excited state giving rise to the resonant fluorescence. (ii) The dimer, trimer, and higher clusters of anthracene all show only excimer emission. When compared to the dimer, the trimer exhibits a peculiar behaviour (structured fluorescence excitation and hole burning spectra, short lifetime and low ionisation efficiency) which has been related to a significant locally excited character of the initially prepared state of the species excited state. (iii) The influence of an intermolecular hydrogen bond on the electron transfer process has been studied in the 2,2,2-trifluoro-1-(9-anthryl)ethanol- dimethylaniline system. A threshold for exciplex formation higher than in the case of the anthracene-dimethylaniline complex is observed.
The zinc selenide and copper selenide thin films were deposited by chemical deposition technique on glass substrates. For both films, sodium selenosulphate was used as a selenide ion source in an alkaline solution. The X-ray diffraction patterns show that the ZnSe has a cubic structure and Cu_3Se_2 film has a tetragonal structure. The relative intensity K_ β / K_ α of zinc and copper selenide thin films has been measured by using a ^{241}Am radioisotope source (75 mCi). The obtained results were compared with the theoretical values.
Electron densities and ion (gas) temperatures on the axis of an arc discharge plasma, produced at atmospheric pressure in a gas mixture of 95% helium and 5% argon, are determined at two arc currents. The evaluation of both main plasma parameters is based on line shape measurements, the ion temperature on the Doppler broadening of selected ArII lines, while the electron density on the Stark broadening of the hydrogen H_{β} line which appear in the spectrum due to hydrogen traces in the applied gases. The significance of reliable plasma diagnostics for determination of atomic structure data is discussed.
We review the current status of the U.S. Primary Frequency Standard, NIST-F1. NIST-F1 is a laser-cooled cesium fountain based frequency standard with an inaccuracy of less thanδ f/f<5×10^{-16}; limited mainly by the radiation field in the room-temperature fountain (blackbody shift). NIST-F1 is one of the best cesium fountains currently contributing to international atomic time, but has reached a point that it is impractical to improve its accuracy substantially. Therefore we are building a new fountain, imaginatively named NIST-F2, with a cryogenic (77 K) Ramsey interrogation zone that lowers the blackbody shift by several orders of magnitude. NIST-F2 is currently undergoing final assembly, and we will discuss our planned (hoped for) performance, which includes frequency inaccuracy ofδ f/f<1×10^{-16}.
The system based on spatially resolved optical emission spectroscopy dedicated for in situ diagnostics of plasma assisted CVD processes is presented in this paper. Measurement system coupled with chemical vapour deposition chamber by dedicated fiber-optic paths enables investigation of spatial distribution of species densities (H_x, H^+, CH, CH^+) during chemical vapour deposition process. Experiments were performed for a various gas inlet configuration at range of microwave power up to 800 W. Spatially resolved optical spectroscopy results showed that inlet configuration based on injecting hydrogen in ECR region and methane in substrate area is the most efficient for H^+ and CH_{3}^{+} excitation. The designed prototype of the spatially resolved optical spectroscopy system enables the high-sensitivity measurements of concentration of the species in the microwave plasma and can be used for optimisation of diamond-like carbon synthesis.
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