Transition Intensities Research Articles

On the prospect of identifying visible emissions from optical measurements of self-assembled QDs

The work presented here focuses on the optical properties of molecular beam epitaxy-grown self-organized InAs quantum dots (QDs). Under low excitation power densities, the photoluminescence (PL) spectrum of the structure under study exhibits a double-peak profile, which has been related to the optical emission from the dots. To properly argue for or against explaining a high energy peak as being the result of different-sized QDs or excited state emissions, a comparative study of the optical properties of a set of two grown QD samples was employed. The laser power dependence of the linearity of the PL intensities of the QD transitions was shown to be very useful in determining the possible origins of the PL sub-bands detectable in a double-peak emission from an ensemble of self-organized QDs. Indeed, the change in the linearity of the dot-luminescence intensity with the increase of the excitation density could give helpful information about the active confinement states from which the dots are emitting. On the other hand, despite the use of very low excitation power densities, the optical measurements of the studied structure have revealed an appearance of a PL signal relating to the radiative emission from the first excited state of the dots. A random pathway of carrier capture by the intrinsic levels of the QDs is thought to be the most likely cause of this aspect.

Exploring the Origins of the Intensity of the OH Stretch-HOH Bend Combination Band in Water.

While the intensity of the OH stretching fundamental transition is strongly correlated to hydrogen-bond strength, the intensity of the corresponding transition to the state with one quantum of excitation in both the OH stretching and HOH bending vibrations in the same water molecule shows a much weaker sensitivity to the hydrogen-bonding environment. The origins of this difference are explored through analyses of the contributions of terms in the expansion of the dipole moment to the calculated intensity. It is found that the leading contribution to the stretch-bend intensity involves the second derivative of the dipole moment with respect to the OH bond length and HOH angle. While this is not surprising, the insensitivity of this derivative to the hydrogen-bonding environment is unexpected. Possible contributions of mode mixing are also explored. While mode mixing leads to splittings of the energies of nearly degenerate excited states, it does not result in significant changes in the sum of the intensities of these transitions. Analysis of changes in the partial charges on the hydrogen atoms upon displacement of the HOH angles shows that these charges generally increase with increasing HOH angle. This effect is partially canceled by a decrease in the charge of the hydrogen atom when a hydrogen bond is broken. The extent of this cancellation increases with the hydrogen bond strength, which is reflected in the observed insensitivity of the intensity of the stretch-bend transition to hydrogen-bond strength.

Luminescence performance of Dy3+ ions incorporated modifier reliant boro-tellurite glasses for white light applications

A diverse array/unique set of Dysprosium (Dy3+) activated alkali boro-tellurite glasses were synthesized for the current study using the conventional approach of glass fabrication, and its potential for photonic applications were explored utilizing optical absorption, emission, and decay measurement methods. In the interest of assessing the Rare Earth (RE) ions bonding behavior with the neighboring metal ligand site, and to establish the glasses ionic/covalence nature, bonding parameters (δ) and Nephelauxetic ratios were computed from the absorption band locations. For the as-prepared samples, the Judd-Ofelt parameters and oscillator strengths were determined in order to scrutinize the uniformity of the ligands surrounding Dy3+ ions. The calculated JO values consistently pursue Ω2 > Ω4 > Ω6 pattern for all samples, indicating their asymptotic character. When excited at 387 nm, the emission spectra demonstrate three intense transitions; 4F9/2→6H15/2, 4F9/2→6H13/2 and 4F9/2→6H11/2. Among them, strong yellow emission was observed owing to the increased transfer of electrons to 6H13/2 level. Besides, using JO parameters, radiative parameters were determined which was followed by lifetime studies to actualize the novel applications. The photoluminescence spectra were employed to estimate the CIE coordinates (x, y) and Yellow/Blue ratio, furthermore the (x, y) values were used to calculate the colour purity followed by colour correlated temperature (CCT). This demonstrates that the prepared samples have the ability to emit neutral white light.

Estimating transition intensity rate on interval-censored data using semi-parametric with EM algorithm approach

Phase IV clinical trials are designed to monitor long-term side effects of medical treatment. For instance, childhood cancer survivors treated with chest radiation and/or anthracycline are often at risk of developing cardiotoxicity during their adulthood. Often the primary focus of a study could be on estimating the cumulative incidence of a particular outcome of interest such as cardiotoxicity. However, it is challenging to evaluate patients continuously and usually, this information is collected through cross-sectional surveys by following patients longitudinally. This leads to interval-censored data since the exact time of the onset of the toxicity is unknown. Rai et al. computed the transition intensity rate using a parametric model and estimated parameters using maximum likelihood approach in an illness-death model. However, such approach may not be suitable if the underlying parametric assumptions do not hold. This manuscript proposes a semi-parametric model, with a logit relationship for the treatment intensities in two groups, to estimate the transition intensity rates within the context of an illness-death model. The estimation of the parameters is done using an EM algorithm with profile likelihood. Results from the simulation studies suggest that the proposed approach is easy to implement and yields comparable results to the parametric model.

Prolonged exercise shifts ventilatory parameters at the moderate-to-heavy intensity transition.

To quantify the effects of prolonged cycling on the rate of ventilation ([Formula: see text]), frequency of respiration (FR), and tidal volume (VT) associated with the moderate-to-heavy intensity transition. Fourteen endurance-trained cyclists and triathletes (one female) completed an assessment of the moderate-to-heavy intensity transition, determined as the first ventilatory threshold (VT1), before (PRE) and after (POST) two hours of moderate-intensity cycling. The power output, [Formula: see text], FR, and VT associated with VT1 were determined PRE and POST. As previously reported, power output at VT1 significantly decreased by ~ 10% from PRE to POST. The [Formula: see text] associated with VT1 was unchanged from PRE to POST (72 ± 12 vs. 69 ± 13 L.min-1, ∆ -3 ± 5 L.min-1, ∆ -4 ± 8%, P = 0.075), and relatively consistent (within-subject coefficient of variation, 5.4% [3.7, 8.0%]). The [Formula: see text] associated with VT1 was produced with increased FR (27.6 ± 5.8 vs. 31.9 ± 6.5 breaths.min-1, ∆ 4.3 ± 3.1 breaths.min-1, ∆ 16 ± 11%, P = 0.0002) and decreased VT (2.62 ± 0.43 vs. 2.19 ± 0.36 L.breath-1, ∆ -0.44 ± 0.22 L.breath-1, ∆ -16 ± 7%, P = 0.0002) in POST. These data suggest prolonged exercise shifts ventilatory parameters at the moderate-to-heavy intensity transition, but [Formula: see text] remains stable. Real-time monitoring of [Formula: see text] may be a useful means of assessing proximity to the moderate-to-heavy intensity transition during prolonged exercise and is worthy of further research.

Photoluminescent Lanthanide(III) Coordination Polymers with Bis(1,2,4-Triazol-1-yl)Methane Linker

A series of new lanthanide(III) coordination polymers with the general formula [Ln(btrm)2(NO3)3]n, where btrm = bis(1,2,4-triazol-1-yl)methane and Ln = Eu3+, Tb3+, Sm3+, Dy3+, Gd3+ were synthesized and characterized by IR-spectroscopy, elemental, thermogravimetric, single-crystal, and powder X-ray diffraction analyses. Europium(III), samarium(III), terbium(III), and gadolinium(III) coordination polymers demonstrate thermal stability up to 250 °C, while dysprosium(III) is stable up to 275 °C. According to single-crystal X-ray diffraction analysis, the ligand exhibits a bidentate-bridging coordination mode, forming a polymeric chain of octagonal metallocycles. The photoluminescence of the free ligand in the polycrystalline state is observed in the ultraviolet range with a quantum yield of 13%. The energy transfer from the ligand to the lanthanide ions was not observed for all obtained coordination polymers. However, there are sharp bands of lanthanide(III) ions in the diffuse reflectance and excitation spectra of the obtained compounds. Therefore, Ln(III) luminescence arises, most probably, from the enhancement of f-f transition intensity under the influence of the ligand field and non-centrosymmetric interactions.

NIR emission and up-conversion spectral studies of Er/Yb co-doped B2O3-Bi2O3-NaF-BaF2 glasses for optical amplifiers and laser applications

Er-singly and Er/Yb-codoped oxyfluoride glasses were prepared by conventional melt-quenching technique. Structural, optical, steady-state and time-resolved spectroscopy studies were performed. The down-conversion (DC) and up-conversion (UC) mechanisms in the Er3+, Yb3+ (single) and Er3+/Yb3+ (co-doped) systems were investigated under 980 nm laser excitation and the energy transfers involved in the emissions of Er3+ and Yb3+ ions were discussed. Judd-Ofelt intensity and radiative factors such as absorption cross-section (σabs) and emission cross-sections (σemi) were evaluated and an enhanced σemi was observed for the co-doped (1 mol% Er/1 mol% Yb) glasses. Gain cross-section profiles were estimated based on σabs and σemi from McCumber theory for the 4I13/2 ↔ 4I15/2 transitions. At the same time, the studied glasses also exhibited intense UC transitions from the excited states of 2H11/2, 4S3/2, and 4F9/2 to the 4I15/2 ground state of Er3+ ions and covered the strong green and red spectral regions. Time-resolved spectroscopic measurements are extended for NIR and UC emission transitions were discussed in detail.

New line intensities for the far infrared bands of the Trans- and Cis-conformer of nitrous acid (HONO), new determination of the Trans-Cis conformer barrier and its impact on the astrophysical detection of nitrous acid in protostellar clouds

The first goal of this work is to improve the determination of the energy difference (ΔECis-Trans) between the ground vibrational state of the Cis- and Trans-HONO conformers of nitrous acid. For this, high resolution spectra were recorded in the 50–200 cm−1 spectral region at three different temperatures, 240, 270 and 296 K. The relative line intensities for the B-type transitions of pure rotational bands of Trans-HONO and Cis-HONO achieved from our measurements were combined in least squares fit computations to those measured previously by Sironneau et al. [Sironneau V, Flaud JM, Orphal J, Kleiner I, Chelin P. Absolute line intensities of HONO and DONO in the far-infrared and re-determination of the Energy Difference between the trans- and cis-species of nitrous acid. J Mol Spectrosc 2010;259:100–104]. In this way, we can significantly improve the accuracy on the HONO conformer energy difference, with a value for ΔECis-Trans = 95.8 ± 9.2 cm−1 compared to SIRΔECis-Trans = 99 ± 25 cm−1 in the previous study of Sironneau et al. The second goal is to generate a line list with “absolute” line intensities for the pure rotational bands in the far infrared region of Trans-HONO and Cis-HONO, with both A- and B-type transitions. This new line list proved to be more robust for an improved detection of HONO in astrophysical objects [Coutens A, Ligterink NFW, Loison JC, Wakelam V, Calcutt H, Drozdovskaya MN, Jørgensen JK, Müller HSP, Van Dishoeck EF, Wampfler SF. The ALMA-PILS survey: First detection of nitrous acid (HONO) in the interstellar medium. Astronomy & Astrophysics 2019;623:L13].

A semi-Markov multistate cure model for estimating intervention effects in stepped wedge design trials.

Multistate models are useful for studying exposures that affect transitions among a set of health states. However, they can be challenging to apply when exposures are time-varying. We develop a multistate model and a method of likelihood construction that allows application of the model to data in which interventions or other exposures can be time-varying and an individual may to be exposed to multiple intervention conditions while progressing through states. The model includes cure proportions, reflecting the possibility that some individuals will never leave certain states. We apply the approach to analyze patient vaccination data from a stepped wedge design trial evaluating two interventions to increase uptake of human papillomavirus vaccination. The states are defined as the number of vaccine doses the patient has received. We model state transitions as a semi-Markov process and include cure proportions to account for individuals who will never leave a given state (e.g. never receive their next dose). Multistate models typically quantify intervention effects as hazard ratios contrasting the intensities of transitions between states in intervention versus control conditions. For multistate processes, another clinically meaningful outcome is the change in the percentage of the study population that has achieved a specific state (e.g. completion of all required doses) by a specific point in time due to an intervention. We present a method for quantifying intervention effects in this manner. We apply the model to both simulated and real-world data and also explore some conditions under which such models may give biased results.

PubPredict: Prediction of progression and survival in oncology leveraging publications and early efficacy data.

In oncology/hematology early phase clinical trials, efficacies were often observed in terms of response rate, depth, timing, and duration. However, the true clinical benefits that eventually support registrational purpose are progression-free survival (PFS) and/or overall survival (OS), the follow-up of which are typically not long enough in early phase trials. This gap imposes challenges in strategies for late phase drug development. In this article, we tackle the question by leveraging published study to establish a quantitative link between early efficacy outcomes and late phase efficacy endpoints. We used solid tumor cancer as disease model. We modeled the disease course of a RECISTv1.1 assessed solid tumor with a continuous Markov chain (CMC) model. We parameterize the transition intensity matrix of a CMC model based on published aggregate-level summary statistics, and then simulate subject-level time-to-event data. The simulated data is shown to have good approximation to published studies. PFS and/or OS could be predicted with the transition intensity matrix modified given clinical knowledge to reflect various assumptions on response rate, depth, timing, and duration. The authors have built a R shiny application named PubPredict, the tool implements the algorithm described above and allows customized features including multiple response levels, treatment crossover and varying follow-up duration. This toolset has been applied to advise phase 3 trial design when only early efficacy data are available from phase 1 or 2 studies.

Non-shockable rhythms: A parametric model for the immediate probability of return of spontaneous circulation

BackgroundCardiac arrest can present with asystole, Pulseless Electrical Activity (PEA), or Ventricular Fibrillation/Tachycardia (VF/VT). We investigated the transition intensity of Return of spontaneous circulation (ROSC) from PEA and asystole during in-hospital resuscitation. Materials and methodsWe included 770 episodes of cardiac arrest. PEA was defined as ECG with >12 QRS complexes per min, asystole by an isoelectric signal >5 seconds. The observed times of PEA to ROSC transitions were fitted to five different parametric time-to-event models. At values ≤0.1, transition intensities roughly represent next-minute probabilities allowing for direct interpretation. Different entities of PEA and asystole, dependent on whether it was the primary or a secondary rhythm, were included as covariates. ResultsThe transition intensities to ROSC from primary PEA and PEA after asystole were unimodal with peaks of 0.12 at 3 min and 0.09 at 6 min, respectively. Transition intensities to ROSC from PEA after VF/VT, or following transient ROSC, exhibited high initial values of 0.32 and 0.26 at 3 minutes, respectively, but decreased.The transition intensity to ROSC from initial asystole and asystole after PEA were both about 0.01 and 0.02; while asystole after VF/VT had an intensity to ROSC of 0.15 initially which decreased. The transition intensity from asystole after temporary ROSC was constant at 0.08. ConclusionThe immediate probability of ROSC develops differently in PEA and asystole depending on the preceding rhythm and the duration of the resuscitation attempt. This knowledge may aid simple bedside prognostication and electronic resuscitation algorithms for monitors/defibrillators.

Ultrafast activation of the double-exchange interaction in antiferromagnetic manganites

In doped manganite systems, strong electronic correlations result in rich phase diagrams where electron delocalization strongly affects the magnetic order. Here, we employ a femtosecond all-optical pump-probe scheme to impulsively photodope the antiferromagnetic parent manganite system CaMnO3 and unveil the formation dynamics of a long-range ferromagnetic state. We resonantly target intense charge transfer electronic transitions in CaMnO3 to photodope the system and probe the subsequent dynamics of both charges and spins using a unique combination of time-resolved terahertz spectroscopy and time-resolved magneto-optical Faraday measurements. We demonstrate that photodoping promotes a long-lived population of delocalized electrons and induces a net magnetization, effectively promoting ferromagnetism resulting from light-induced carrier-mediated short-range double-exchange interactions. The picosecond set time of the magnetization, much longer than the electron timescale, and the presence of an excitation threshold are consistent with the formation of ferromagnetic patches in an antiferromagnetic background.

Sickness absence transitions among Swedish twins with back, neck or shoulder pain and common mental disorders applying a multi-state approach

We aimed to investigate transitions to and from sickness absence, or disability pension among individuals with back, neck, or shoulder pain and/or with common mental disorders (CMDs), and the role of familial (genetics and shared environment) influences on the transitions. Swedish twins born 1935–1985 who responded to pain and CMDs survey items (N = 41,516) were followed on average 8.7 years for sickness absence states in national registers. Multi-state Cox regression models were applied for three exposure groups: pain, CMDs, and presence of both, compared to unexposed. Exposure discordant twin pairs, stratified by zygosity, were analysed to assess the role of familial factors. Hazard Ratios (HR) with 95% confidence intervals and transition intensities were calculated. HRs were similar for transitions between states among those with pain or CMDs. The highest HRs were for transitions from entry to sickness absence and sickness absence to disability pension among those with both pain and CMDs (HRs: 1.61 and 1.43, respectively). Higher HRs for dizygotic compared to monozygotic twins for the first transition to sickness absence and for altering back to not being sickness absent indicate familial confounding. Back, neck, or shoulder pain and/or CMDs indicate a higher risk to become sickness absent and for repeated sickness absence episodes over time compared to unaffected.

Harnessing the Energy of Visible Light to Promote LMCT of Cu(II) Species for Intramolecular Dehydrogenative Lactonization of Biaryl-2-carboxylic Acids

Earth-abundant copper salts, in recent years, have attracted the attention of the scientific community with their ability to perform ligand-to-metal charge transfer (LMCT) upon light excitation, thereby eliminating the necessity of a high activation energy barrier required in thermal approaches. Herein, we have reported an application of photoinduced LMCT of Cu(II) species toward the synthesis of benzocoumarin derivatives from 2-aryl benzoic acids via intramolecular dehydrogenative coupling. Existence of light-induced LMCT is confirmed by using detailed mechanistic studies, which include lowering of the d–d transition intensity upon photoexcitation (in UV–visible spectroscopic analysis) and drop-down of the EPR signal intensity on sequential irradiation. Moreover, X-ray photoelectron spectroscopy (XPS) studies reveal the photochemical conversion of Cu(II) to Cu(I) through LMCT. A large number of diverse functional groups could easily be tolerated under this newly developed protocol affording very good yield of the desired benzocoumarins. Additionally, the bulk-scale synthesis of a metabolite compound urolithin A further extends the applicability of this light-induced methodology.

Role of MCD and Mössbauer Spectroscopy in the Explanation of the Properties of a Highly Soluble (μ-Oxo)bis[tetra(tert-butyl)(phthalocyaninato)iron(III)] Complex, Its Pyridine Adduct, and Redox Forms Oxidized under Anaerobic Conditions in Non-Coordinating Solvents.

Solid-state Mössbauer spectra of a highly soluble (μ-oxo)bis[tetra(tert-butyl)(phthalocyaninato)iron(III)] complex 1 ((PctBuFe)2O) consist of two doublets that represent bent geometry in μ-oxo(1) (1a, ΔEQ = 0.43 mm/s, T = 10 K) and linear geometry in μ-oxo(2) (1b, ΔEQ = 1.40 mm/s, T = 10 K) isomers with the ratio between two isomers depending on the purification method. Both isomers were found to be diamagnetic and transform entirely to the 1a isomer in solution. The room- and low-temperature magnetic circular dichroism (MCD) spectra of 1a μ-oxo(1) show one Faraday A- and one B-term between 670 and 720 nm, which correlate with the 690 nm band and 709 nm shoulder observed in the UV-vis spectrum of this compound. UV-vis and MCD spectra of 1a are almost independent of the temperature. Both 1a and 1b are diamagnetic between room temperature and 4 K. Electrochemical experiments show up to three oxidations and up to four reduction processes in 1a. Its oxidation under spectroelectrochemical or chemical (in the absence of oxygen-containing oxidants) conditions in non-coordinating solvents results in the formation of broad NIR bands around 1195 nm (first oxidation) and 1264 nm (second oxidation). The MCD spectra of the redox-active species show a Faraday B-term signal with negative amplitude in this region and are very different from those in the monomeric PctBu(1-)FeIIIX2 complexes 5X (X = Cl- or CF3CO2-). The pyridine adduct of 1a ((PyPctBuFe)2O; 2Py) is paramagnetic (μB = 2.19, g = 2.11, and J = -6.1 cm-1) and has a major peak at 627 nm of its UV-vis spectrum, which is associated with a MCD pseudo A-term. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations, along with the exciton coupling theory, were used to explain the unusually red-shifted intense transitions in 1a as well as the H-aggregate-like spectra of the pyridine adduct 2Py.

Effect of ZnS nanoparticles on the spectroscopic transitions of Ho3+ ions in sol-gel silica matrix

ZnS NPs and Ho3+ co-doped silica matrices are prepared by room temperature sol-gel method. The fabricated matrices are characterized structurally by X-ray diffractometry, Transmission electron microscopy, Energy dispersive X-ray analysis and Fourier transform infrared spectroscopy. Structural studies reveal the presence of ZnS NPs in the Ho3+ co-doped silica matrices. Judd Ofelt analysis of UV–Visible absorption spectra shows that the phenomenological Judd Ofelt intensity parameters Ωt, which illustrate the intensities for transitions in lanthanides and actinides in solids as well as solutions follow the trend Ω2>Ω4>Ω6. Enhancement in the Ω2 parameter with ZnS NP concentration indicates higher asymmetry and a stronger covalent environment of Ho3+ ions in the studied matrix, compared to some popular hosts. The four distinct PL emission bands of Ho3+ observed in the studied matrices show a strong dependence on ZnS NP concentration, with 0.67 M of ZnS as the optimum concentration. The enhancement in the PL emissions with ZnS NPs is attributed to the network modification and sensitization of Ho3+ ions by the NPs. Sensitization through energy transfer also increases the lifetime of the excited state, as observed from the PL decay study. The decrease of PL emission beyond optimum ZnS concentration is most likely due to the self-quenching of ZnS NPs. The upconversion study shows enhancement in Ho3+ luminescence up to 14 times with ZnS co-doping; indicating the viability of the fabricated matrix for their application in UC devices as well.

Radiation intensity of optical transitions in the germanium/silicon nanosystems with germanium quantum dots

Dipole-allowed optical transitions between quasi-stationary and stationary states, which occur over the spherical surface of a single germanium quantum dot (QD) embedded in a silicon matrix, are theoretically investigated. These optical electron transitions, which occur in the real space of the silicon matrix, allow for solving the problem of a significant increase in the radiation intensity in germanium/silicon heterostructures with germanium QDs. Long-lived quasistationary and stationary states will make it possible to realize high-temperature quantum Bose-gases states in the nanosystem under study.

Impact of offspring and their educational level on readmission and death among older adults with chronic obstructive pulmonary disease: a nationwide cohort study using multistate survival models

BackgroundIt is well described that there is social inequality in the disease course of chronic obstructive pulmonary disease (COPD), but the impact of social relations is less explored. We aimed...

Study of photoluminescence behaviors and Judd-Ofelt analysis of Eu3+ doped double perovskite Ba2GdSbO6 phosphor for highly pure and strong red-light generation

An array of Eu3+ doped Ba2GdSbO6 luminescent materials have been synthesized by the conventional solid-state (high temperature) reaction route. Surface morphology has been studied via Field Emission Scanning Electron Microscopy. The structural and optical behaviors have been studied using X-Ray Diffraction (XRD), FTIR, Raman spectroscopy, Diffuse reflectance spectroscopy, Photoluminescence excitation (PLE), and Photoluminescence emission (PL) spectra. FTIR and Raman's spectra provided the chemical functional group and different vibrational levels within the samples. The calculated optical band gap was 4.40 eV and 4.47eV for pure and optimized samples respectively. Photoluminescence emission curves have been recorded for 245 nm of excitation wavelength and the highest emission peak was focused at 595 nm corresponding to 5D0 → 7F1. Similarly, the Photoluminescence excitation curves were monitored at the emission wavelength of 595 nm and a broad charge transfer band (CTB) was observed from 230 to 285 nm. The emission spectra show the concentration quenching effect beyond the 2 mol% Eu3+ concentration. The corresponding transitions of Eu3+ were further utilized to obtain the Judd-Ofelt (J-O) transition intensity parameters Ωλ (λ = 2, 4) for each sample. Additionally, by studying decay kinetics, the average lifetime of the red emission of the samples has been evaluated, which was 4.622 ms. The photometric study also reveals the CIE coordinates, color purity and CCT values of the proposed phosphor material. Thus, the results obtained from these characterizations, suggest that the prepared sample may behave as a potential candidate in the case of UV-excited red light-emitting phosphor material for light-emitting diodes and field emission devices.

Photo-physical properties of Pr (III) chelates of substituted nitrobenzoic acid and nitrophenols

Electronic absorption and emission spectra were recorded for chelates of Pr (III) with 2-hydroxy-4-nirobenzoic acid, 3-hydroxy-4-nitrobenzoic acid, 4-hydroxy-3-nitrobenzoic acid, 4-methyl-2-nitrophenol, 4-chloro-2-nitrophenol and 5-fluoro-2-nitrophenol in various M: L stoichiometry and for different pH. Intensity and energy of intraconfigurational 4fn transitions have been determined from the absorption spectra. The spectroscopic parameters like Slater-Condon (Fk), Racah (Ek), Lande (ζ4f) and Judd-Oflet parameters Ωλ (λ=2, 4, 6) have been computed using statistical method like partial regression method. The Judd-Oflet intensity parameters and fluorescence spectra have been used to calculate radiative life time (τ) of two excited states 3P0 and 1D2. From the fluorescence spectra of the chelates, effective line width (Δλeff) spontaneous emission probability (A), fluorescence branching ratio (β) and stimulated emission cross section (σ) have been determined for three optical transition 3P0-3H4, 3P0-3H5 and 1D2-3H4. Spectroscopic and intensity parameters were studied with respect to the ligand field symmetry and degree of bond covalency.