Calculated Line Strengths Research Articles

A comprehensive study of ferroelectric, dielectric and optical properties of europium-doped SBD metal- organic framework

The synthesis of Europium-doped Strontium based benzene dicarboxylate dimethylformamide metal–organic framework- Eu([Sr(μ-BDC)(DMF)])- with short form as Eu:SBD@MOF was carried out using the solvothermal method. The investigation involved characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), CHN analysis, and energy-dispersive X-ray (EDX) elemental analysis. The results confirmed the formation of metal–organic crystals in the framework. The XRD characterization shows good alignment with the simulated pattern of SBD. The experimental absorption spectrum displays distinct transitions of the Eu (III) ion alongside transitions of the ligands. Calculations of line strengths for all observed transitions have been conducted. The Judd-Ofelt theory has been employed to determine intensity parameters, transition probabilities, branching ratios, and radiative lifetimes for the Eu: SBD@MOF. These JO parameters further aid in calculating various excited state properties. When excited by ultraviolet and visible photons, the complex exhibits emission in the red region respectively. The crystal’s dielectric loss and dielectric constant were investigated for their frequency dependence. It was observed that by virtue of DMF, a molecule linked to the crystal, a synthesized MOF exhibits a good dielectric characteristic and when the temperature is raised to 558 K, the dielectric constant drops sharply as DMF molecule could not stand after this temperature. Further ferroelectric studies reveal that the Eu: SBD@MOF has maximum polarization of 0.27 C/cm2 which is greater than Rochelle salt and other MOF’s. Exploring the broadband dielectric response of metal–organic frameworks (MOFs) open up new avenues in research, potentially leading to innovative applications in smart optoelectronics, terahertz sensors, high-speed telecommunications, and microelectronics.

CI-MBPT line strengths and atomic probabilities for some transitions of neutral iodine

Iodine is a promising alternative to expensive xenon as a propellant for electric propulsion devices. Iodine optical spectroscopy is a valuable diagnostic tool for optimization of the iodine propellant. Recently, some measurements have been conducted with cells containing iodine plasma, and iodine atomic absorption at several wavelengths (911, 906, 206 and 1315 nm) was measured with a Ti:sapphire laser. Motivated by these experiments and future applications, we have calculated line strengths and atomic probabilities for the transitions between different types of 5s25p5, 5s25p46s, 5s25p46p and 5s25p45d states of atomic iodine, using configuration-interaction many-body perturbation theory. Since experimental transition data for atomic iodine are only available for a relatively small number of transitions, we also performed calculations for the bromine atom, to further validate our approach. We found good agreement between our theory and available experimental data for both elements in most cases. Therefore, we believe that our predicted line strengths and transition probabilities are quite reliable and will be useful for iodine spectroscopy.

Quantitative analysis of gas phase molecular constituents using frequency-modulated rotational spectroscopy.

Rotational spectroscopy has been used for decades for virtually unambiguous identification of gas phase molecular species, but it has rarely been used for the quantitative analysis of molecular concentrations. Challenges have included the nontrivial reconstruction of integrated line strengths from modulated spectra, the correlation of pressure-dependent line shape and strength with partial pressure, and the multiple standing wave interferences and modulation-induced line shape asymmetries that sensitively depend on source-chamber-detector alignment. Here, we introduce a quantitative analysis methodology that overcomes these challenges, reproducibly and accurately recovering gas molecule concentrations using a calibration procedure with a reference gas and a conversion based on calculated line strengths. The technique uses frequency-modulated rotational spectroscopy and recovers the integrated line strength from a Voigt line shape that spans the Doppler- and pressure-broadened regimes. Gas concentrations were accurately quantified to within the experimental error over more than three orders of magnitude, as confirmed by the cross calibration between CO and N2O and by the accurate recovery of the natural abundances of four N2O isotopologues. With this methodology, concentrations of hundreds of molecular species may be quantitatively measured down to the femtomolar regime using only a single calibration curve and the readily available libraries of calculated integrated line strengths, demonstrating the power of this technique for the quantitative gas-phase detection, identification, and quantification.

The water-carbon monoxide dimer: new infrared spectra, ab initio rovibrational energy level calculations, and an interesting in-termolecular mode.

Bound state rovibrational energy level calculations using a high-level intermolecular potential surface are reported for H2O-CO and D2O-CO. They predict the ground K = 1 levels to lie about 20 (12) cm-1 above K = 0 for H2O-CO (D2O-CO) in good agreement with past experiments. But the first excited K = 1 levels are predicted to lie about 3 cm-1 below their K = 0 counterparts in both cases. Line strength calculations also indicate that mid-infrared transitions from the K = 0 ground state to this seemingly anomalous excited K = 1 state should be observable. These predictions are strikingly verified by new spectroscopic measurements covering the C-O stretch region around 2200 cm-1 for H2O-CO, D2O-CO, and HOD-CO, and the O-D stretch region around 2700 cm-1 for D2O-CO, HOD-CO, and DOH-CO. The experiments probe a pulsed supersonic slit jet expansion using tunable infrared quantum cascade laser or optical parametric oscillator sources. Discrete perturbations in the O-D stretch region give an experimental lower limit to the binding energy D0 of about 340 cm-1 for D2O-CO, as compared to our calculated value of 368 cm-1. Wavefunction plots are presented to help understand the intermolecular dynamics of H2O-CO. Coriolis interactions are invoked to explain the seemingly anomalous energies of the first excited K = 1 levels.

Luminescence enhancement of Pr3+ doped sol-gel silica glass as a result of Al3+ co-doping

Praseodymium (Pr3+) doped silica glass with varying Aluminum (Al3+) concentrations have been prepared using sol-gel technique. The glass samples produced have density (2.2 g/cm3) and refractive index (1.46) similar to that of fused silica. Judd-Ofelt parameters Ω2, Ω4 and Ω6 were obtained from the absorption spectrum in the visible region and used to calculate line strengths of transitions involved in cross-relaxation. Analyses of cross-relaxation mechanisms suggest higher probability for the 1D2 state. Photoluminescence emissions in the visible and NIR region were observed under 450 nm excitation. Slow annealing to 1000 °C minimizes hydroxyl quenching by reducing hydroxyl content thereby improving the luminescence. Al3+ co-doping also significantly enhance the luminescence, especially the 1D2 emission which is evidence of reduction in cross-relaxation.

Line strengths of QED-sensitive forbidden transitions in B-, Al-, F- and Cl-like ions

The magnetic dipole (M1) line strength between the fine-structure levels of the ground configurations in B-, F-, Al- and Cl-like ions are calculated for the four elements argon, iron, molybdenum and tungsten. Systematically enlarged multiconfiguration Dirac-Hartree-Fock~(MCDHF) wave functions are employed to account for the interelectronic interaction with the Breit interaction included in first-order perturbation theory. The QED corrections are evaluated to all orders in $\alpha Z$ utilizing an effective potential approach. The calculated line strengths are compared with the results of other theories. The M1 transition rates are reported using accurate energies from the literature. Moreover, the lifetimes in the range of millisecond to picoseconds are predicted including the contributions also from the transition rate due to the E2 transition channel. The discrepancies of the predicted rates from those available from the literature are discussed and a benchmark dataset of theoretical lifetimes is provided to support future experiments.

Line Lists for LiF and LiCl in the X1Σ+ Ground State

Abstract Vibration–rotation line lists for 6LiF, 7LiF, 6Li35Cl, 6Li37Cl, 7Li35Cl, and 7Li37Cl in the X 1Σ+ ground states have been prepared. The rovibrational energy levels have been calculated using potential energy surfaces determined by direct potential-fitting employing the rotational and rovibrational transition frequencies of all isotopologues, and required the inclusion of Born–Oppenheimer breakdown terms. Dipole moment functions calculated ab initio at the MRCI/aug-cc-pwCV5Z level have been used for line strength calculations. Partition functions for temperatures up to 5000 K have been calculated. LiF and LiCl are predicted to be present in the atmospheres of hot rocky exoplanets, brown dwarfs, and cool stars.

Convergence of normal mode variational calculations of methane spectra: Theoretical linelist in the icosad range computed from potential energy and dipole moment surfaces

Accurate basis set convergence of first-principles predictions of rotationally resolved spectra at high energy range is a common challenging issue for variational methods. In this paper, a detailed convergence study for the methane spectra is presented both for vibrational and rotational degrees of freedom as well as for intensities. For this purpose, we use our previously reported nine-dimensional potential energy and dipole moment surfaces of the methane molecule [Nikitin et al. Chem Phys Lett 2011;501:179–86; 2013;565:5–11]. Vibration–rotation calculations were carried out using variational normal mode approach with a full account of the Td symmetry. The aim was to obtain accurate theoretical methane line lists for the wavenumber range beyond currently available spectra analyses. The focus of this paper is the complicated icosad range (6280–7900cm−1) containing 20 bands and 134 sub-bands where over 90% of experimental lines still remain unassigned. We provide variational line lists converged to a “spectroscopic precision” for icosad transitions for T=80K and T=296K. The first one contains 70300 lines and the second one 286170 lines with the intensity cut-off 10−29cm−1/(moleculecm−2) with Jmax=18. An average error in line positions of theoretical predictions up to J=15 is estimated as 0.2–0.5cm−1 from the comparisons with currently analyzed bands. Ab initio line strength calculations give the integrated intensity 4.37×10−20cm−1/(moleculecm−2) at T=80K for the sum of all icosad bands. This is to be compared to the integrated intensity 4.36×10−20cm−1/(moleculecm−2) of the experimental icosad line list recorded in Grenoble University [Campargue et al., J Mol Spectrosc 2013;291:16–22] using very sensitive laser techniques. The shapes of absorption bands are also in a good qualitative agreement with experimental spectra.

On the calculation of line strengths, oscillator strengths and lifetimes for very large principal quantum numbers in hydrogenic atoms and ions by the McLean–Watson formula

As a sequel to an earlier study (Hey 2009 J. Phys. B: At. Mol. Opt. Phys. 42 125701), we consider further the application of the line strength formula derived by Watson (2006 J. Phys. B: At. Mol. Opt. Phys. 39 L291) to transitions arising from states of very high principal quantum number in hydrogenic atoms and ions (Rydberg–Rydberg transitions, n > 1000). It is shown how apparent difficulties associated with the use of recurrence relations, derived (Hey 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2641) by the ladder operator technique of Infeld and Hull (1951 Rev. Mod. Phys. 23 21), may be eliminated by a very simple numerical device, whereby this method may readily be applied up to n ≈ 10 000. Beyond this range, programming of the method may entail greater care and complexity. The use of the numerically efficient McLean–Watson formula for such cases is again illustrated by the determination of radiative lifetimes and comparison of present results with those from an asymptotic formula. The question of the influence on the results of the omission or inclusion of fine structure is considered by comparison with calculations based on the standard Condon–Shortley line strength formula. Interest in this work on the radial matrix elements for large n and n′ is related to measurements of radio recombination lines from tenuous space plasmas, e.g. Stepkin et al (2007 Mon. Not. R. Astron. Soc. 374 852), Bell et al (2011 Astrophys. Space Sci. 333 377), to the calculation of electron impact broadening parameters for such spectra (Watson 2006 J. Phys. B: At. Mol. Opt. Phys. 39 1889) and comparison with other theoretical methods (Peach 2014 Adv. Space Res. in press), to the modelling of physical processes in H II regions (Roshi et al 2012 Astrophys. J. 749 49), and the evaluation bound–bound transitions from states of high n during primordial cosmological recombination (Grin and Hirata 2010 Phys. Rev. D 81 083005, Ali-Haïmoud and Hirata 2010 Phys. Rev. D 82 063521, Ali-Haïmoud 2013 Phys. Rev. D 87 023526).

Spectral properties of a few F-like ions

Aims. We intend to provide accurate data for the oscillator strengths, transition probabilities, lifetimes, and hyperfine shifts of the atomic energy levels in the fluorine (F)- like Ti, V, Cr, Mn, Co, Ni, Cu, Zn, and Mo ions for the diagnostic of the astrophysical plasma. Furthermore, we propose these ions for probing possible variation in the fine structure constant (αe) by observing their transition lines from the distant astronomical objects. Methods. We have employed an all-order perturbative method in the relativistic coupled-cluster framework using the Dirac-Coulomb Hamiltonian for calculating the atomic wave functions in the considered F-like ions. We adopted the Fock-space formalism to account for the correlation effects among the occupied electrons by allowing all possible singly and doubly excited configurations in two steps: first considering the correlations between the electrons in a closed-shell configuration, and second constructing the openshell configurations of the first three low-lying states in the considered atomic systems by removing the respective electron from the core orbitals. This procedure enormously simplifies the computational complexity and overcomes the need to select important configuration state functions in determining the atomic state functions in contrast to a truncated configuration interaction method. Moreover, corrections from the frequency-independent Breit interaction and the lowest order quantum electrodynamic effects are incorporated self-consistently. Results. We present the calculated ionization potential energies of the electrons that are detached to form the above considered F-like ions. The correctness of our estimated results are ensured by comparing them with the available experimental values and other calculations. From these calculations, we evaluate the relativistic sensitivity coefficients that we propose here to be used for probing possible temporal variation of the fine structure constant (αe) through the precise astrophysical observation of the spectral lines of the transitions involving the above low-lying states. The accuracies of these sensitivity coefficients are appraised from the comparison of our calculated energies with the experimental values. We also present the line strengths by calculating the reduced matrix elements of the allowed transitions and of the M1 and E2 forbidden transitions. By combining our calculated line strengths with the observed wavelengths, we determine the oscillator strengths, transition probabilities, and lifetimes of the first two excited states of the above ions and compare them with the other theoretical calculations. The hyperfine splittings of the states are also presented by calculating their magnetic dipole and electric quadrupole hyperfine structure constants.

Effects of the electron correlation and Breit and hyperfine interactions on the lifetime of the2p53sstates in neutral neon

In the framework of the multiconfiguration Dirac-Hartree-Fock method, we investigate the transition properties of four excited states in the $2p^53s$ configuration of neutral neon. The electron correlation effects are taken into account systematically by using the active space approach. The effect of higher-order correlation on fine structures is shown. We also study the influence of the Breit interaction and find that it reduces the oscillator strength of the $^3P^o_1 - ^1S_0$ transition by 17%. It turns out that the inclusion of the Breit interaction is essential even for such a light atomic system. Our ab initio calculated line strengths, oscillator strengths and transition rates are compared with other theoretical values and experimental measurements. Good agreement is found except for the $^3P^o_2 - ^1S_0$ M2 transition for which discrepancies of around 15% between theories and experiments remain. In addition, the impact of hyperfine interactions on the lifetimes of the $^3P^o_0$ and $^3P^o_2$ metastable states is investigated for the $^{21}$Ne isotope (I=3/2). We find that hyperfine interactions reduce the lifetimes drastically. For the $^3P^o_0$ state the lifetime is decreased by a factor of 630.

Computational study of the rovibrational spectrum of (OCS)2

In this paper, we report a new intermolecular potential energy surface and rovibrational transition frequencies and line strengths computed for the OCS dimer. The potential is made by fitting energies obtained from explicitly correlated coupled-cluster calculations and fit using an interpolating moving least squares method. The rovibrational Schroedinger equation is solved with a symmetry-adapted Lanczos algorithm and an uncoupled product basis set. All four intermolecular coordinates are included in the calculation. On the potential energy surface we find, previously unknown, cross-shaped isomers and also polar and non-polar isomers. The associated wavefunctions and energy levels are presented. To identify polar and cross states we use both calculations of line strengths and vibrational parent analysis. Calculated rotational constants differ from their experimental counterparts by less than 0.001 cm(-1).

Transition probabilities and oscillator strengths of E1 transitions in Fe XII and Fe XIV

Non-orthogonal orbitals in the multiconfiguration Hartree–Fock approach are used to calculate line strengths, oscillator strengths and transition probabilities for E1 transitions among the fine-structure levels of the 3s 23p 3, 3s3p 4, 3s 23p 23d, 3s3p 33d, 3p 5 and 3s 23p3d 2 configurations in Fe XII and 3s 23p, 3s3p 2, 3s 23d, 3p 3, 3s3p3d, 3p 23d, 3s3d 2, 3p3d 2, 3s 24s, 3s 24p, 3s3p4s and 3s 24d configurations in Fe XIV. The lifetimes of excited levels belonging to these configurations of Fe XII and Fe XIV are also presented. An accurate representation of the levels has been obtained using spectroscopic and correlation radial functions. The wavefunctions exhibit large correlations and significant dependence of one-electron valence orbitals due to both the total and intermediate terms. The relativistic corrections are included through the one-body and two-body operators in the Breit–Pauli Hamiltonian. Progressively larger calculations are performed to check for important electron correlation contributions and for convergence of results. The atomic wavefunctions give excitation energies which are in close agreement with experiment. The present oscillator strengths and transition probabilities compare very well with previous large scale calculations.

H 216O line strengths revisited: ν2 and 2 ν2– ν2 at 6 μm

The necessity to revisit water spectroscopy at 6 μm was prompted by recent work indicating that some prior measurements of H 2 16O line strengths (ranging through seven orders of magnitude) had larger than expected systematic errors for the stronger transitions. To investigate this, linestrengths of stronger transitions were re-measured (with 14 new H 2O spectra recorded with a Bruker 125 HR Fourier transform spectrometer at the Jet Propulsion Laboratory) and combined with re-analyzed prior results (obtained at higher optical densities from 32 spectra recorded with the FTS at Kitt Peak). Systematic differences for some of the older data sets were identified and corrected. In this paper, an internally-consistent sampling of 1243 selected line strengths are reported for (0 1 0)–(0 0 0) and (0 2 0)–(0 1 0) transitions between 783 and 2378 cm −1. To confirm experimental precisions, observed and calculated line strengths are compared.

Oxygen in dense interstellar gas

Oxygen is the third most abundant element in the universe, but its chemistry in the interstellar medium is still not well understood. In order to critically examine the entire oxygen budget, we attempt here initially to estimate the abundance of atomic oxygen, O, in the only one region, where molecular oxygen, O2, has been detected to date. We analyse ISOCAM-CVF spectral image data toward rho Oph A to derive the temperatures and column densities of H2 at the locations of ISO-LWS observations of two [OI] 3P_J lines. The intensity ratios of the (J=1-2) 63um to (J=0-1) 145um lines largely exceed ten, attesting to the fact that these lines are optically thin. This is confirmed by radiative transfer calculations, making these lines suitable for abundance determinations. For that purpose, we calculate line strengths and compare them to the LWS observations. Excess [OI] emission is observed to be associated with the molecular outflow from VLA 1623. For this region, we determine the physical parameters, T and N(H2), from the CAM observations and the gas density, n(H2), is determined from the flux ratio of the [O I]63um and [O I]145um lines. For the oxygen abundance, our analysis leads to essentially three possibilities: (1) Extended low density gas with standard ISM O-abundance, (2) Compact high density gas with standard ISM O-abundance and (3) Extended high density gas with reduced oxygen abundance, [O/H] ~ 2E-5. As option (1) disregards valid [O I] 145um data, we do not find it very compelling; we favour option (3), as lower abundances are expected as a result of chemical cloud evolution, but we are not able to dismiss option (2) entirely. Observations at higher angular resolution than offered by the LWS are required to decide between these possibilities.

First observation of 628 CO 2 isotopologue band at 3.3 μm in the atmosphere of Venus by solar occultation from Venus Express

The new ESA Venus Express orbiter is the first mission applying the probing technique of solar and stellar occultation to the atmosphere of Venus, with the SPICAV/SOIR instrument. SOIR is a new type of spectrometer used for solar occultations in the range 2.2–4.3 μm. Thanks to a high spectral resolving power R ∼ 15 , 000 – 20 , 000 (unprecedented in planetary space exploration), a new gaseous absorption band was soon detected in the atmospheric transmission spectra around 2982 cm −1, showing a structure resembling an unresolved Q branch and a number of isolated lines with a regular wave number pattern. This absorption could not be matched to any species contained in HITRAN or GEISA databases, but was found very similar to an absorption pattern observed by a US team in the spectrum of solar light reflected by the ground of Mars [Villanueva, G.L., Mumma, M.J., Novak, R.E., Hewagama, T., 2008. Icarus 195 (1), 34–44]. This team then suggested to us that the absorption was due to an uncatalogued transition of the 16O 12C 18O molecule. The possible existence of this band was soon confirmed from theoretical considerations by Perevalov and Tashkun. Some SOIR observations of the atmospheric transmission are presented around 2982 cm −1, and rough calculations of line strengths of the Q branch are produced, based on the isotopic ratio measured earlier in the lower atmosphere of Venus. This discovery emphasizes the role of isotopologues of CO 2 (as well as H 2O and HDO) as important greenhouse gases in the atmosphere of Venus.

Gemini Near-Infrared Spectroscopy of Luminousz~ 6 Quasars: Chemical Abundances, Black Hole Masses, and MgiiAbsorption

We present Gemini near-infrared spectroscopic observations of six luminous quasars at z = 5.8 to ∼6.3. Five of them were observed using Gemini South GNIRS, which provides a simultaneous wavelength coverage of 0.9-2.5 μm in cross-dispersion mode. The other source was observed in the K band with Gemini North NIRI. We calculate line strengths for all detected emission lines and use their ratios to estimate gas metallicity in the broad-line regions of the quasars. The metallicity is found to be supersolar, with a typical value of ∼4 Z⊙, and a comparison with low-redshift observations shows no strong evolution in metallicity up to z ∼ 6. The Fe II/Mg II ratio of the quasars is 4.9 ± 1.4, consistent with low-redshift measurements. We estimate central black hole masses of 109-1010 M⊙ and Eddington luminosity ratios of order unity. We identify two Mg II λλ2796, 2803 absorbers with rest equivalent width W > 1 Å at 2.2 < z < 3 and three Mg II absorbers with W > 1.5 Å at z > 3 in the spectra, with the two most distant absorbers at z = 4.8668 and 4.8823, respectively. The redshift number densities (dN/dz) of Mg II absorbers with W > 1.5 Å are consistent with no cosmic evolution up to z > 4.

Intensities of inter-Stark transitions in activated crystals

A scheme of calculation of line strengths for indirect electric dipole transitions between Stark states of impurity ions in dielectric crystals is proposed. It is shown that knowledge of the three semiphenomenological Judd-Ofelt parameters of a crystalline system is sufficient for quantitative calculations. The formulas obtained were approved for YAG:Nd3+ crystals based on calculation of the spectroscopic characteristics of the lines of the inter-Stark transitions 4 F 3/2 → 4 I 9/2 and 4 F 3/2 → 4 I 11/2.

Phase shift cavity ring down at low temperatures: Vibration–rotation overtone absorption of H–D (Δ v = 4) at 297 and 105 K

Phase shift cavity ring down (PS-CRD) spectroscopy has been used for the detection of a vibrational–rotational overtone transition ( v = 0 → 4) of H–D at 297 and 105 K. The PS-CRD technique at low temperatures involves an optical cavity attached to a cryostat where the static cell and mirrors of the optical cavity are all at the same temperature. A novel design allows the alignment of the mirrors of the optical cavity at low temperatures without disrupting the vacuum in the chamber surrounding the cell. The peak absorption lines were corrected for distortion because the bandwidth (fwhm) of the laser in our experiment exceeds the width of the absorption lines. The calculated line strengths of the rotational transitions are in good agreement with literature values.

Photoionization studies of the atmospherically important species N and OH at the Elettra synchrotron radiation source

In this paper angularly resolved photoelectron spectra (PES) and constant-ionic-state (CIS) spectra are presented for the atmospherically important species N and OH. The natural width Γ, line shape parameters q and ρ 2 and discrete oscillator strengths f have been measured for the members of the N*[2s2p 3( 5S), np] ( 4P) ← N( 4S) autoionizing resonances for n = 5–10. The n = 5 parameters calculated in this work are in good agreement with the values obtained previously whereas for the resonances with n = 6–10 the values of these parameters are reported for the first time. The asymmetry parameter ( β) for the first band of N atoms, the N +( 3P) ← N( 4S) ionization, has also been measured in the photon energy range of the above autoionizing resonances. For OH, CIS spectra have been recorded for the first photoelectron band corresponding to the ionization OH +(X 3Σ −, v + = 0) ← OH(X 2Π, v″ = 0). In these spectra, rotationally partially resolved bands associated with OH*(a 1Δ3d, v′ = 0) ← OH(X 2Π, v″ = 0) resonances have been observed. Suggestions for their assignment are made on the basis of their positions and band simulations which use rotational line strength calculations.