Variation Of Oscillator Strength Research Articles

Micelle Sensitized Physicochemical Studies on Erbium(III) Complexes with Hypoglycemic Sulfonylurea Drugs

Hypoglycemic sulfonylurea derivatives ligands viz. glimepiride, glibenclamide, gliclazide and glipizide show interaction with lanthanide metal Er (III) in non-micellar and micellar medium. Anionic, cationic and non-ionic surfactant micellar media show great variation in oscillator strength of Er (III) with hypoglycemic sulfonylurea drugs as reflected in UVVisible absorption spectra. Interpretation of UVVisible absorption spectra produced that 4G11/2 ← 4I15/2 and 2H11/2 ← 4I15/2 electronic transition bands show different behavior on account of oscillator strength (P) compared to other electronic f-f transitions, depicted as hypersensitive peaks which are characterized as ratio of Pmicellar / PDMF. Exploitation of different parameters viz: oscillator strength (P), Judd-Ofelt parameter Tλ, nephelauxetic effect 𝛽 and bonding parameter b1/2 from absorption spectra supports the covalency characters in metal ligand Er (III)-drugs doped systems to a greater extent. Thermodynamic exploits of hypersensitive transition correlate the spectroscopic data via Work function A, Thermodynamic efficiency of transition TET and Partition function Q. Thermodynamic parameters notify the microscopic behaviour of Er (III)- sulfonylurea drugs.

Mixed ionic–electronic effect on up–conversion in Er3+/V4+ co–doped Na2O–CaO–B2O3 glasses with enhanced red emission

Optical absorption and emission properties of 20Na2O–20CaO–(59 – x)B2O3–xV2O5–1Er2O3 (x = 0 – 2.5 mol%) (Series A) and 20Na2O–20CaO–(58.5 – y)B2O3–1.5V2O5–yEr2O3 (y = 0 – 3.0 mol%) (Series B) glass systems were examined to elucidate the effect of Er2O3 co–doping with V2O5 in the mixed ionic–electronic (MIE) glasses. The absorption spectra of both glass series exhibited 10 significant bands, which corresponded to the f–f transition of Er3+ ions with an additional weak absorption band attributed to V4+ energy transition. The up–conversion PL spectra for the glasses under 779 nm excitation displayed 3 emissions bands centered at 518, 556 and 647 nm due to the emission from the energy levels of Er3+. The enhanced emission at 647 nm (red region) that corresponded to the 4F9/2 → 4I15/2 of the Er3+ transition for all glasses was suggested due to energy transfer from V4+ to Er3+ ions. For Series A, the variation of oscillator strength (fexp) and Judd–Ofelt parameters (Ω2,4,6) showed almost similar trend, which exhibit a maximum at x = 0.5 mol% V2O5. PL intensity was highest for sample x = 0.5 mol% but abruptly drops to the minimum at x = 1.5 mol%. The decrease in PL was possibly influenced by the MIE effect. Meanwhile, for Series B glasses, general decrease was observed in fexp and Judd–Ofelt parameters except for Ω6 upon Er2O3 addition. The PL intensity increased and reached a maximum at y = 2.0 mol% before subsequently decreased with further addition of Er2O3 (y = 3.0 mol%) due to concentration quenching.

Optical Absorption, Kinetics and Thermodynamic Studies of Pr(III) and Nd(III) Ions with N-Acetyl L-Cysteine in Presence of Ca(II) ions

Interaction of N-acetyl-L-cysteine (NAC) with Pr3+ (Pr(NO3)3·6H2O) and Nd3+ (Nd(NO3)3·6H2O) ions are studied in presence of Ca2+ (Ca(NO3)3·4H2O) ion in an aqueous and organic solvent by applying the spectroscopic technique for quantitative probe of 4f-4f transition. The complexation was determined by the variation in the intensities of 4f-4f absorption spectral bands and by applying the change of symmetric properties of electronic-dipole known as Judd-Ofelt parameters Tλ (λ = 2,4,6). On the addition of Ca2+ ion in the binary complexation of praseodymium and neodymium with N-acetyl-L-cysteine (NAC) there is an intensification of bands which shows the effect of Ca2+ toward the heterobimetallic complex formation. Other parameters like Slater-Condon (Fk), bonding (b1/2), the Nephelauxetic ratio (β), percentage covalency (δ) are also used to correlate the complexation of metals with N-acetyl-L-cysteine (NAC). With the minor change in coordination around Pr3+ and Nd3+ ions, the sensitivity of 4f-4f bands is detected and further used to explain the coordination of N-acetyl-L-cysteine (NAC) with Pr3+ and Nd3+ in presence of Ca2+. The variation in oscillator strength (Pobs), energy (Eobs) and dipole intensity parameter help in supporting the heterobimetallic complexation of N-acetyl-L-cysteine. In kinetics investigation, the rate of the complexation of both hypersensitive and pseudo-hypersensitive transition is evaluated at various temperature in DMF solvent. The value of the thermodynamic parameters such as ΔHo, ΔSo and ΔGo and activation energy (Ea) also evaluated.

IARJSET - Science, Engineering and Technology

Studies on the oscillator strength as Judd-Oflet parameters (1,2) were carried out for some f-f transitions specially on Hypersensitive or pseudoquadorpolar transitions for Pr (III) complexes with N and O containing ligands(viz:2-Hydroxyquinoline,8-Hydroxyquinoline, and 8-Aminoquinoline) in organic (Et-OH) as well as micellar medium as a doped system. The oscillator strength was calculated by Judd-Of let method. The variation in oscillator strength (Pobsx10 ) as well as in Judd-Ofelt Parameter T2 x10 9 was reported as solvent changed.

Analysis of quantum well size alteration effects on slow light device based on excitonic population oscillation

In this paper we investigate the effects of quantum well size changes on slow light device properties. The principle properties such as center frequency and slow down factor of a slow light device are affected by changing the size of quantum well. In this way, the effects of quantum well size on Oscillator Strength and binding energy of exciton are considered separately. First, we investigate the variations in oscillator strength of exciton due to different quantum well size. Second, exciton binding energy level shift due to size of quantum well is investigated. According to this analysis, we have developed a new method for tuning slow light device bandwidth center frequency and slow down factor. Analysis and simulation of a basic GaAs/AlGaAs quantum wells optical slow light device based on excitonic population oscillation shows that size of quantum wells could tune both of the frequency properties and slow down factor of an optical slow light device. Simulation results show that slow down factor and oscillation strength of exciton are proportional to each other in direct manner. Moreover, decreasing the quantum well width, causes enhancement in binding energy of excitons. These achievements are useful in optical nonlinearity enhancements, all-optical signal processing applications and optical communications.

Effects of Quantum well Size Alteration on Excitonic Population Oscillation Slow Light Devices Properties

This paper investigates the effects of quantum well size changes on center frequency and slow down factor of an slow light device. In this way, we consider the quantum well size alteration effects on oscillator strength and binding energy of exciton. First, we investigate the variations in oscillator strength of exciton due to different quantum well size. Second, exciton binding energy level shift due to size of quantum well is investigated. According to this analysis, we have developed a new method for tuning slow light device bandwidth center frequency and slow down factor. Analysis and simulation of a basic GaAs/AlGaAs quantum wells optical slow light device based on excitonic population oscillation shows that size of quantum wells could tune both of the frequency properties and slow down factor of an optical slow light device. In our simulation with 34 quantum wells each with the width of 60?, we have received the slow down factor of more than 60,000. These achievements are useful in optical nonlinearity enhancements, all-optical signal processing applications and optical communications.

DFT based computational study on the excited state intramolecular proton transfer processes in o-hydroxybenzaldehyde

Potential energy (PE) curves for the intramolecular proton transfer in the ground (GSIPT) and excited (ESIPT) states of o-hydroxybenzaldehyde (OHBA) were studied using DFT-B3LYP/6-31G(d) and TD-DFT-B3LYP/6-31G(d) level of theory, respectively. Our calculations suggest the non-viability of ground state intramolecular proton transfer in this compound. Excited states PE calculations support the ESIPT process in OHBA. The contour PE diagram and the variation of oscillator strength along the proton transfer co-ordinate support the dual emission in OHBA. Our calculations also support the experimental observations of Nagaoka et al. [S. Nagaoka, U. Nagashima, N. Ohta, M. Fujita, T. Takemura, J. Phys. Chem. 92 (1988) 166], i.e. normal emission of the title compound comes from S 2 state and the red-shifted proton transfer band appears from the S 1 ′ state. ESIPT process has also been explained in terms of HOMO and LUMO electron density of the enol and keto tautomer of OHBA and from the potential energy surfaces.

Calculation of electric dipole intensity parameter to explore some interaction between hard metal ions Pr(III) and Nd(III) with π-electron density of butene-1,4 and butyne-1,4-diols in non-aqueous solutions: An absorption spectral study

Pr(III) and Nd(III) are hard acceptors in HSAB (hard and soft acid base) sense and hence are known to exhibit practically a little affinity towards electrons. At the same time these metal ions show strong preference for oxygen donor chelating ligands. The ligands chosen for this study are structurally related diols, viz. butane-1,4, butene-1,4 and butyne-1,4-diols which form identical seven membered chelate ring by coordinating to metals in a bidentate manner through oxygen on 1 and 4 positions of the diol molecules. Complexation of these diols with Pr(III) and Nd(III) was carried out in DMF, CH3OH, CH3CN and their equimolar binary mixtures using comparative absorption spectrophotometry of 4f–4f transitions. The variation of oscillator strengths (P) of different 4f–4f bands as well as the magnitude and variation of Judd–Ofelt electric dipole intensity parameters (Tλ, λ=2, 4, 6) was discussed. They correlate the interaction between the metal 4f-orbitals of Pr(III) and Nd(III) with the π-electron densities of the double and triple bonds present in butene-1,4 and butyne-1,4-diols, respectively. The value of empirical intensity parameter [Tλ(complex)/Tλ (aquo)] was calculated and its plot against oscillator strength (P) is drawn.

Spectroscopic study of lanthanide(III) complexes with carboxylic acids

The complexation of trivalent lanthanides with aromatic (mellitic, pyromellitic, hemimellitic, trimellitic, trimesic, phthalic, isophthalic, terephthalic and benzoic) carboxylic acids was studied by luminescence and absorption spectroscopic methods and luminescence lifetime measurements. Stability constants with these carboxylate ligands were calculated from the 7F 0– 5D 0 excitation spectra of Eu(III). The stability constant of the 1:1 complexes showed linear correlation with the basicity of the ligand. The luminescence decay constants indicate that the ligands with carboxylates in the ortho position are bidentate, replacing two water molecules from the metal upon complexation. Benzoate and terephthalate are unidentate. Isophthalate and trimesate replace approximately 1.5 water molecules, suggesting greater binding capability of these ligands due to the contribution from the non-binding carboxylate group(s). The oscillator strengths in the hypersensitive transition range of Nd(III) and Ho(III) complexed with these ligands were non-linearly proportional to the effective ligand basicity. Ligand polarizability, along with other factors, are proposed as responsible for the variation in oscillator strength in these complexes.

Studies of the Electronic Structure of Metallocene-Based Second-Order Nonlinear Optical Dyes

This paper describes a simple orbital picture for understanding the optical transitions and the second-order nonlinear optical response of metallocene-based chromophores of the form metallocene−(π-bridge)−acceptor, and experimental studies to test this model. From a combination of UV photoelectron spectroscopy, cyclic voltammetry, and density functional calculations, it is deduced that the three highest occupied orbitals are little perturbed from the parent metallocenes, that the HOMO-3 is a π-orbital delocalized between the metallocene cyclopentadienyl ring and the unsaturated bridge, and that the LUMO is acceptor based. The lowest energy transition in the UV/visible/near-IR spectra of these compounds is assigned to a metal-to-acceptor transition, while the higher energy transition is attributed to a transition to the acceptor-based LUMO from the delocalized HOMO-3 orbital. The variations in oscillator strength can be rationalized by considering the low-energy transition as borrowing intensity from the high-energy transition. Stark spectroscopy confirms that large dipole moment changes are associated with both transitions, as expected from our assignment. These dipole moment changes indicate that, according to the perturbation theory-derived expression for the first hyperpolarizability, β, both transitions contribute significantly to the observed optical nonlinearity.

Modeling the contribution of quantum confinement to luminescence from silicon nanoclusters

We present a model for the luminescence spectrum of silicon nanoclusters. We propose that the major contribution to luminescence is from radiative recombination of confined excitons (quantum confinement). Utilizing the effective mass approximation we consider the variation in oscillator strength with cluster size and the associated change in the number of available free carriers. By varying both the mean cluster size and size distribution of silicon nanoclusters, the luminescence spectra are modeled to a good fit. We compare our model with experimental photoluminescence and electroluminescence data from this group and from others.

Carrier density dependent effects on the Fermi energy edge singularity in quantum wells containing two occupied subbands

Optical transitions into the second electronic subband of a wide modulation doped quantum well (QW) are shown to exhibit behaviour characteristic of a Fermi edge singularity for upper subband densities ⪆ 0.4 × 10 11 cm −2. Variations in oscillator strength of such transitions with lower subband Landau level filling are demonstrated to be small.

Application of the relativistic random-phase approximation to atoms of the neon isoelectronic sequence

The relativistic random-phase approximation is applied to the calculation of excitation energies and oscillator strengths for the $2{p}^{6}^{1}S_{0}\ensuremath{-}2{p}^{5}3s^{1}P_{1}$, $^{3}P_{1}$ and $2{p}^{6}^{1}S_{0}\ensuremath{-}2{p}^{5}3d^{1}P_{1}$, $^{3}P_{1}$, $^{3}D_{1}$ transitions of elements of the neon isoelectronic sequence. The results are compared with those of other calculations and experiment. The variation of oscillator strength along the isoelectronic sequence is depicted for each of the transitions. Anomalous behavior occurs which is attributed to level crossings.