Calculated Oscillator Strengths Research Articles

Observational constraints on the origin of the elements

Context. The chemical composition of the Sun is required in the context of various studies in astrophysics, among them in the calculation of standard solar models (SSMs) used to describe the evolution of the Sun from the pre-main-sequence to its present age. Aims. In this work, we provide a critical re-analysis of the solar chemical abundances and corresponding SSMs. Methods. For the photospheric values, we employed new high-quality solar observational data collected with the IAG facility, state-of-the art non-equilibrium modelling, new oscillator strengths, and different atmospheric models, including the MARCS model, along with averages based on Stagger and CO5BOLD 3D radiation-hydrodynamics simulations of stellar convection. We performed new calculations of oscillator strengths for transitions in O I and N I. For O I, which is a critical element with regard to the interior models, calculations were carried out using several independent methods. We investigated our results in comparison with the previous estimates. Results. We find an unprecedented agreement between the new estimates of transition probabilities, thus supporting our revised solar oxygen abundance value. We also provide new estimates of the noble gas Ne abundance. In addition, we discuss the consistency of our photospheric measurements with meteoritic values, taking into account the systematic and correlated errors. Finally, we provide revised chemical abundances, leading to a new value proposed for the solar photospheric present-day metallicity of Z/X = 0.0225, which we then employed in SSM calculations. We find that the puzzling mismatch between the helioseismic constraints on the solar interior structure and the model can be resolved thanks to this new chemical composition.

Detailed spectral evaluation of rare earth co-doped glasses for photonic applications

We report herein the detailed evaluation of structural and radiative properties of a series of Sm3+ and Gd3+ co-doped lead phosphate glasses having the compositions (58.2-2x) PbO - 40 P2O5 - 1.8 Al2O3 - x Sm2O3 - x Gd2O3, where x = 0.4–1.4 mol%. The synthesized glass samples were investigated for their structural properties using XRD and FTIR spectroscopy. The oscillator strength of the glass samples was evaluated from UV–Vis absorption spectra. Method of least squares fit between experimental and calculated oscillator strengths had been utilized to obtain Judd-Ofelt intensity parameters W2, W4 and W6 for determining the local structure and nature of bonding around rare-earth ions. The radiative and lasing properties were evaluated from intensity parameters such as probability of radiative transition, branching ratio and radiative lifetime. The emission transitions from the excited level 4G5/2 of samarium to the lower manifolds 6H5/2 and 6H7/2 were observed to be most suitable for photonic applications due to their higher values of electric as well as magnetic dipole radiation transition probability, branching ratio, and cross section of stimulated emission. Glass sample PPASG4 had shown enhanced radiative properties as compared to some previously reported glass configurations with similar Sm2O3 content; which suggests it to be potential candidate for lasing applications.

Investigation of Electronic Structural, Thermodynamic Properties, Spectroscopic Analysis (FT-IR, FT-RAMAN, UV-Vis) of Nitromethane

In the present work, the computational investigation of Electronic molecular structural, Thermochemistry, Spectroscopical analysis: (FT-IR, FT-RAMAN, UV-Vis) of Nitromethane (CH3NO2) are performed by Gaussian and the calculations are compared with the existing experimental and theoretical data available for the molecule. Optimized structure, fundamental scaled and unscaled vibrational frequencies, Mulliken charges are modeled using HF method, DFT (Density Functional Theory), and different basis sets. Study of thermodynamic functions: partition function, thermal energy, entropy, and specific heat capacity of the Nitromethane as a function of temperatures and MEP (molecular electrostatic potential) are obtained using density functional theory, B3LYP/ Basis Set-1 (6-311++G(d,p) ). The B3LYP/ Basis Set-1 (6-311++G(d,p)) basis sets calculations used here matches well with the experimental infrared spectra data over the other calculations. The oscillator strength and energy calculations alongwith spectroscopic analysis in terms of UV-Visible spectrum on the optimized structure of Nitromethane using TD-DFT, time-dependent DFT are performed in this paper.

Localized excitons in ZnMnO

Lines a, b, c, d and impurity absorption edge of ZnMnO for sigma- and π-polarizations of light in temperature interval of 7-300 K were registered in this paper. Intensive lines aπ and asigma are clearly observed in interval of 7-100 K, while other lines are observed only at low temperatures. For determination of type of optical transitions, to which excitonic lines a, b, c, d are corresponding the calculation of oscillator strength of most intensive lines was made. Lines aπ and asigma have Lorentz form, parameters of this form were calculated with OriginPro 9.1 program. The energy of impurity absorption edge was determined. Lines a, b, c and d were analyzed in model of Mn2+-4O2- cluster. Optical transitions take place from antibonding (p+d5)*-states in forbidden gap to state, which is splitted from the bottom of conduction band of ZnMnO. Electron-hole pairs which are localized inside the cluster are called as local excitons. Keywords: zinc oxide, localized excitons, antibonding states.

Локализованные экситоны в ZnMnO

Lines a, b, c, d and impurity absorption edge of ZnMnO for σ-and π-polarizations of light in temperature interval of 7 – 300 К were registered in this paper. Intensive lines aπ and aσ are clearly observed in interval of 7-100 K, while other lines are observed only at low temperatures. For determination of type of optical transitions, to which excitonic lines a, b, c, d are corresponding the calculation of oscillator strength of most intensive lines was made. Lines aπ and aσ have Lorentz form, parameters of this form were calculated with OriginPro 9.1 program. The energy of impurity absorption edge was determined. Lines a, b, c и d were analyzed in model of Mn2+ - 4O2- cluster. Optical transitions take place from antibonding (p+d5)*-states in forbidden gap to state, which is splitted from the bottom of conduction band of ZnMnO. Electron-hole pairs which are localized inside the cluster are called as local excitons.

Fluorescence Spectral Properties of Methyl Orange in Homogeneous Media.

The methyl orange [C14H14N3SO3Na], an azo dye exhibited strong emission and large Stokes shift in various solvents, and the largest shift (Δλ = 125.51nm or Δν = 9297cm-1) was obtained in the water. The UV-visible spectra of the dye showed the absorption in the range (33,333 - 20,000) cm-1. We found that solvent effects on the absorption wavelength are consistent. The bathochromic shift in water and the hypsochromic shift in methanol observed in the absorption (43 nm) as well as in the fluorescence (42 nm) spectra predict the strong solute-solvent interaction. The fluorescence quantum yield (ɸf) was decreased from 24% in DMSO to 5% in water. The fluorescent properties of this dye are strongly solvent dependent, the wavelength of minimum fluorescence emission (λem = 435.51nm) shifts to the red. The maximum and minimum calculated oscillator strength is 32% with (Ɛmax = 29011 M-1cm-1) and 11% (Ɛmax = 6682 M-1cm-1) in methanol and DMSO, respectively. Protonated solvents without exception give a shorter lifetime and lower quantum yield. The average excited-state lifetime of the dye was found maximum (τav = 5.36 ns) in DMSO. Also, fluorescence lifetime was combined to deduce the radiative and non-radiative decay rate.

Spectroscopic Characterization of the First and Second Excited States of the HOSO Radical.

The spectroscopic properties of the ground and first two excited states of the HOSO radical are investigated using the internally contracted multireference configuration interaction method, including the Davidson correction (MRCI+Q) and explicit treatment of the electron correlation (MRCI-F12). The vertical and adiabatic excitation energies are also determined. The results reveal that both the 1 2A and 2 2A electronic states contain minima in their potential energy surfaces. The first excited state 1 2A possesses a nonplanar structure and has an adiabatic excitation energy of 1.45 eV (855 nm), lying in the near-infrared region. The second excited state 2 2A has a planar geometry and an adiabatic excitation energy of 2.91 eV (426 nm) existing in the visible region. The calculated oscillator strengths for the vertical electronic excitations to the 1 2A (327 nm) and 2 2A (270 nm) states are 0.003 and 0.022, respectively, indicating experimental intensity should be observed. The small but non-negligible Franck-Condon factors for excitations ∼300 nm, and the broad and intense absorption feature in the 225-275 nm region suggest that detection of the HOSO radical with electronic spectroscopy may be feasible.

Optical properties and laser prediction of strontium bismuth borate glasses doped with neodymium Ions

Neodymium strontium bismuth borate glass samples were prepared using the traditional technique of high-temperature melting. The optical absorption spectra of the studied samples were recorded at room temperature. Analyzing the recorded spectra, important optical parameters were determined; for example, refractive index, optical dielectric constant, the indirect optical band gap and Urbach energy. The calculated Judd-Ofelt parameters exhibited trend which is Ω2 > Ω6 > Ω4. Moreover, the experimental and calculated oscillator strengths of the radiative 4f transitions, their lifetimes τ, refractive indices n, the emission, absorption cross sections and the branching ratio β were all determined and investigated. Calculations of the optical gain coefficient for all emission peaks revealed the possibility to use the present glass in laser emission materials and optical communication applications.

First principle calculations of structural, elastic, electronic and optical properties of cubic Cd1-x-yZnxHgyTe triangular quaternary alloys and their compounds

Structural, elastic, electronic and optical properties of zinc blende Cd1-x-yZnxHgyTe quaternary alloys and their allied compounds are calculated with DFT based FP-LAPW approach. Structural and mechanical properties are computed with PBE-GGA potentials, while mBJ-GGA and GGA + U potentials are employed to compute electronic and optical properties. All the thermodynamically stable specimens show mechanical stability, elastic anisotropy, ductility, mixed type of bonding etc. Each alloy shows direct (Γ-Γ) band gap (Eg) with EgmBJ−GGA>EgGGA+U. Electrons play dominant role over holes in carrier transportation. Exclusive or collective effort of the Te-5p→Zn-5s, Cd-6s, Hg-7s electronic transitions contribute peaks in the ε2(ω) spectra of any specimen. Specimen with higher band gap possesses lower zero-frequency limits, but requires higher critical point energies in different optical spectra and vice versa. Calculated oscillator strength of quaternary alloys show presence of sufficient number of electrons in unoccupied conduction states beyond 27.0 eV during optical excitations.

Structural and optical studies on Dy3+ ions doped alkali lead borophosphate glasses for white light applications

Dy3+ ions doped alkali lead borophosphate glasses with chemical compositions of (45-x) H3BO3+20P2O5+10Al2O3+10PbO+15Li2CO3+xDy2O3 (where x = 0.0, 0.1, 0.25, 0.50, 1.0 and 2.0 wt%) have been prepared by conventional melt quenching technique and their physical, structural and spectroscopic behavior were studied systematically through XRD, FTIR, SEM with EDAX, optical absorption, luminescence and decay measurements. The density and refractive index increase with increasing of Dy3+ ions concentration and accordingly creating more non-bridging oxygen (NBOs) into glass matrix. X-ray diffraction study proves the amorphous nature of the prepared glasses. The FTIR study reveals the presence of BO4, PO4 vibrational groups and the bending of B–O–P, P–O–P units. The surface morphology and existence of elements in the prepared glasses have been studied through SEM with EDAX. The absorption spectra exhibit nine peaks with hypersensitive transition corresponding to 6H15/2→6F11/2 at around 1270 nm. The Judd-Ofelt (JO) theory is used to calculate the calculated oscillator strengths, JO intensity parameters, radiative transition probabilities, stimulated emission cross-section and branching ratio for the present glasses. The JO intensity parameters follow the trend as Ω2>Ω6>Ω4. The luminescence spectra of the glass sample displayed three emission peaks with high intensity are centered at 478 nm and 574 nm respectively. These attractive luminescence features of the proposed glasses in the white region verified using CIE 1931 diagram useful for the development of white light applications. The decay measurements of the prepared glasses for the state 4F9/2 were measured and exhibits both single and non-exponential behavior.

Energy Levels, Wavelengths, Probabilities, and Oscillator Strengths of Transition for Ge-Like Pd, Ag, and Cd Ions

High-accuracy calculations of energy levels, wavelengths, probabilities, and oscillator strengths of transition of resonance lines for Ge-like Pd, Ag, and Cd ions have been performed. For the accurate treatment of relativity, the contributions of Breit interactions and quantum electrodynamics correction were considered. The calculated values of energy levels and wavelengths, including core–valence corrections, are found to be in excellent agreement with other theoretical and experimental values for Ge-like Pd, Ag, and Cd ions. The number of energy levels and wavelengths we considered is larger than that of any other theoretical calculations. The transition probabilities are also given where no other theoretical results and experimental values are available.

Shock wave and modelling study of the UV spectra of perfluorocarbon iodides and perfluorocarbon radicals

The UV absorption spectrum of C2F5I was studied in shock waves over the temperature range 580–1200 K and, together with room temperature data, was represented in extended Sulzer–Wieland form. As a case study, the work illustrates the properties of high-temperature UV absorption continua for use in kinetics experiments in shock waves. A comparison with experimental data for CF3I and their representation is made. Quantum-chemical model calculations of positions and oscillator strengths are tested and, besides CF3I and C2F5I, applied also to spectra of C2F4I, C2F4, CF2I, C2F2, C2F, CF2, CFI, CF, and IF. Likewise, modelling and experimental results for the high-temperature UV absorption spectra of CF3 and C2F5 radicals are considered.

Electron Impact Excitation of Singly Charged Indium Ion

We study electron impact excitation of In\({}^{+}\) using relativistic distorted wave method and report cross sections for 37 transitions among the fine-structure levels of \(5s^2\), \(5s5p\), \(5s5d\), \(5s6s\) and \(5s6p\) configurations at the scattered electron energies upto 200 eV. The bound state wavefunctions of the target ion are obtained within multi-configuration Dirac-Fock approach. Our calculated oscillator strengths are compared with the results from the NIST database and other theoretical calculations. Cross sections are fitted with an analytical formula and the fitting parameters are made available for their possible applications in plasma modeling.

Intersubband transitions in spherical quantum dot quantum well nanoparticle

In this paper, we present results about electronic spectra and optical properties of one-electron spherical quantum dot-quantum well (QDQW) structure. Investigated structure consists of CdSe core surrounded by ZnS shell and caped by infinitely high electron potential barrier which can be a good model for any high enough potential barriers. This specific QDQW structure is determined by CdSe and ZnS properties (effective masses and conductive band offset) and the core size and the shell thickness. We present calculation results for one-electron ground (1s) state and the first excited (1p) state transition. For this transition we have calculated oscillator strengths and linear and third-order nonlinear intersubband optical absorption coefficients for various core and shell size i.e. different CdSe core radii and ZnS barrier thickness. Change in core and shell dimensions induces change in one-electron wave function i.e. electron energy states and localization for both 1s and 1p states. As a result, intersubband 1s–1p transition of this system is greatly dependent on the core and shell size. For very small core radii, less than 0.7 nm, and core radii over 1.5 nm the most probable intersubband transition is 1s–1p, but in the region between 0.7 and 1.5 nm core radii, transitions from 1s to other p states dominates. Investigated properties depend mostly on the core radius. These results connect the dot structure and the optical properties of this particular structure. This behavior is than an illustration of similar systems.

Stellar laboratories

Context.Accurate atomic data is an essential ingredient for the calculation of reliable non-local thermodynamic equilibrium (NLTE) model atmospheres that are mandatory for the spectral analysis of hot stars.Aims.We aim to search for and identify for the first time spectral lines of copper (atomic numberZ= 29) and indium (Z= 49) in hot white dwarf (WD) stars and to subsequently determine their photospheric abundances.Methods.Oscillator strengths of Cu IV–VIIwere calculated to include radiative and collisional bound-bound transitions of Cu in our NLTE model-atmosphere calculations. Oscillator strengths of In IV - VIwere compiled from the literature.Results.We newly identified 1 Cu IV, 51 Cu V, 2 Cu VI, and 5 In Vlines in the ultraviolet (UV) spectrum of DO-type WD RE 0503−289. We determined the photospheric abundances of 9.3 × 10−5(mass fraction, 132 times solar) and 3.0 × 10−5(56 600 times solar), respectively; we also found Cu overabundances in the DA-type WD G191−B2B (6.3 × 10−6, 9 times solar).Conclusions.All identified Cu IV-VIlines in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths. With the detection of Cu and In in RE 0503−289, the total number of trans-iron elements (Z> 28) in this extraordinary WD reaches an unprecedented number of 18.

Accurate determination of energy levels, hyperfine structure constants, lifetimes and dipole polarizabilities of triply ionized tin isotopes

We have investigated the energies, magnetic dipole hyperfine structure constants (Ahyf) and electric dipole (E1) matrix elements of a number of low-lying states of triply ionized tin (Sn3+) by employing relativistic coupled-cluster theory. Contributions from the Breit interaction and lower-order quantum electrodynamic (QED) effects in the determination of the above quantities are also given explicitly. These higher-order relativistic effects are found to be important for the accurate evaluation of energies, while only QED contributions are seen to contribute significantly to the determination of Ahyf values. Our theoretical results for the energies are in agreement with one of the measurements but show significant differences for some states with another measurement. Reported Ahyf will be useful in guiding the measurements of hyperfine levels in the stable isotopes of Sn3+. The calculated E1 matrix elements are further used to estimate the oscillator strengths, transition probabilities and dipole polarizabilities (α) of many states. Large discrepancies between the present results and previous calculations of oscillator strengths and transition probabilities are observed among a number of states. The estimated α values will be useful for carrying out high precision measurements using the Sn3+ ion in future experiments.

Semi-empirical model potential study of Rydberg transitions in gold one-electron spectrum

Semi-empirical model potential calculations of oscillator strengths for Rydberg transitions in principal, sharp and diffuse series of gold one-electron spectrum are presented. Relativistic effects are fully included through solving Dirac equations and core–valence electron correlation is represented in core polarization picture by appropriate part in model potential. The dipole-moment operator of transition is modified in accordance. Systematic trends are investigated in oscillator strengths along the spectral series showing hydrogen-like behavior for large n∗ effective quantum number of upper states of transitions. The so-called Cooper minimum in oscillator strengths is observed for principal series transitions. The influence of core–valence correlation (core polarization) on oscillator strengths along the spectral series is studied in detail​ demonstrating its importance even for transitions to rather highly excited Rydberg states with n≈18. In addition, excitation energies for some levels which positions in the neutral gold spectrum is unknown so far, are also predicted.

Luminescent properties of Sm3+ doped metal fluoro phosphate glasses

Trivalent Samarium doped multi-component Cadmium Lead Sodium Fluoro-Phosphate glass was prepared and characterized through optical absorption, emission and excitation measurements. With the support of Judd-Ofelt theory, the intensity parameters and other radiative parameters were determined using optical absorption spectra from visible region to NIR region and reasonable less deviation obtained between the experimental and calculated oscillator strengths. The emission and excitation spectra of Sm3+ have been recorded under the excitation wavelength λex =399 nm and the emission wavelength λem =596 nm. The emission of Sm3+ in this phosphate host is assigned to the transition from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2 levels and relative parameters like branching ratio, emission cross section were calculated. In addition to that 1 mol% of MgO also added to the host and compared with the obtained results. GSm5 glass emits high intense red emission for 4G5/2 → 6H7/2 transition suggests the suitability of these glasses for red light emission or laser applications in visible region.

The influence of Ba2+ and Sr2+ ions with the Dy3+ ions on the optical properties of lead borate glasses: experimental and Judd–Ofelt comparative study

Two glasses compositions (50B2O3–30PbO–20SrO–xDy) and (50B2O3–30PbO–20BaO–xDy) where x=0.0.5%, and 1.0% in wt.% ratio were prepared using melt quenching technique in order to investigate the effect of Ba2+ and Sr2+ ions in Dy3+ ions doped lead borate glass. The optical properties such as bandgap and the refractive index distribution were examined using UV–vis-NIR absorption spectroscopy. The FTIR absorption spectra of all prepared samples were similar except for the metallic bands in the fingerprint region. The obtained experimental data were compared with theoretical data calculated by Judd–Ofelt framework. The Judd–Ofelt parameters Ωλ (λ=2, 4 and 6) were calculated and the trend was Ω2<Ω4<Ω6 which is the common trend. The experimental oscillator strength (fexp), the calculated oscillator strength (fcal), the estimated refractive indexes (n) at each transition, the lifetime of radiative transitions (τ), the branching ratio (β), the absorption cross-section (σabs(λ)) and the emission cross-section (σemis(λ)) were also estimated and discussed. The optical gain coefficient (G(λ)) was calculated not only for the most intense emission transition but also other emission peaks. The obtained results indicated that the prepared samples are promising materials for laser emission and optical communication applications.

Room Temperature Gas Phase Infrared Spectra of H-bonded Oligomers of Methanol

Formation of various hydrogen bonded oligomers of methanol at room temperature was investigated with the aid of gas phase infrared spectroscopy. In parallel quantum chemical vibrational analyses were performed to identify them and calculate their thermodymical properties. Above 20 torr several weak features appear to the lower wavenumber of the O-H stretch fundamental. Comparing with previous literature reports we ascribe them due to higher (di, tri and tetrameric) oligomeric forms of methanol. Increasing temperature above 298 K in an isochoric condition diminishes the intensity of the observed oligomeric bands, which provides the basis for identification of these bands as originating from H-bonded oligomers. Open and cyclic forms of di, tri and tetrameric forms of methanol were optimized and their anharmonic frequencies were calculated using second order vibrational perturbation theory. Additionally, their binding energies and the enthalpy of formations were also derived from the thermochemical analysis. Experimental enthalpy of formations were evaluated from the variation of integrated band areas with temperature. From the calculated oscillator strengths and the area under each band, the partial pressures of different H-bonded methanol oligomers at room temperature have been obtained for the first time. We obtained in 100 torr total pressure at 298 K the partial pressures of dimer, trimer and tetramer are 0.005, 0.0122 and 0.076 torr, respectively.