Absorption Oscillator Strengths Research Articles

Spectroscopy, crystal-field, and transition intensity analyses of the C[formula omitted](O[formula omitted]) centre in Er[formula omitted] doped CaF2 crystals

Erbium ions in crystals show considerable promise for the technologies that will form the backbone of future networked quantum information technology. Despite advances in leveraging erbium’s fibre-compatible infrared transition for classical and quantum applications, the transitions are, in general, not well understood. We present detailed absorption and laser site-selective spectroscopy of the C3v(O2−) centre in CaF2:Er3+ as an interesting erbium site case study. The 4I15/2Z1→4I13/2Y1 transition has a low-temperature inhomogeneous linewidth of 1 GHz with hyperfine structure observable from the 167Er isotope. A parametrized crystal-field Hamiltonian is fitted to 34 energy levels and the two ground state magnetic splitting factors. The wavefunctions are used to perform a transition intensity analysis and electric-dipole parameters are fitted to absorption oscillator strengths. Simulated spectra for the 4I11/2→4I15/2 and 4I13/2→4I15/2 inter-multiplet transitions are in excellent agreement with the experimentally measured spectra. The 4I13/2 excited state lifetime is 25.0ms and the intensity calculation is in excellent agreement with this value.

Fully relativistic energies, transition properties, and lifetimes of lithium-like germanium

Abstract Employing two fully relativistic methods, the multi-reference configuration Dirac–Hartree–Fock (MCDHF) method and the relativistic many-body perturbation theory (RMBPT) method, we report energies and lifetime values for the lowest 35 energy levels of the (1s2)nl configurations (where the principal quantum number n = 2–6 and the angular quantum number l = 0, …, n–1) of lithium-like germanium (Ge XXX), as well as complete data on the transition wavelengths, radiative rates, absorption oscillator strengths, and line strengths between the levels. Both the allowed (E1) and forbidden (magnetic dipole M1, magnetic quadrupole M2, and electric quadrupole E2) ones are reported. The results from the two methods are consistent with each other and align well with previous accurate experimental and theoretical findings. We assess the overall accuracies of present RMBPT results to be likely the most precise ones to date. The present fully relativistic results should be helpful for soft x-ray laser research, spectral line identification, plasma modeling and diagnosing. The datasets presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j00113.00135.

Study of photosensitizer dyes for high-performance dye-sensitized solar cells application: A computational investigation

Dye-sensitized solar cells (DSSCs) offer a promising, cost-effective alternative to conventional photovoltaic systems. Organic sensitizers, capable of capturing a broad spectrum of sunlight, are key components in DSSCs, but their development and testing are often time-consuming and expensive. Quantum chemical calculations, specifically Density Functional Theory (DFT), have emerged as valuable tools to evaluate potential dye candidates, streamlining the design process and reducing costs. This study investigated the molecular structures and photophysical properties of three common dye classes used in high-performance DSSCs: natural pigments, anthocyanidin pigments, and squaraine dyes. Employing DFT and time-dependent DFT (TD-DFT) at the B3LYP/6–31G level, key parameters such as the HOMO-LUMO energy gap, free energy differences for electron injection and dye regeneration, short-circuit current density, total reorganization energy, and open-circuit voltage were analyzed. Additionally, maximum absorption wavelengths and oscillator strength values were calculated. Our findings provide valuable insights into the optical and electrical properties of these natural dyes, aiding DSSC manufacturers in selecting optimal sensitizers. This research highlights the potential of computational methods in accelerating dye development and improving the overall efficiency of DSSC technology.

The study of atomic structure parameters for [formula omitted] = 4 - [formula omitted] = 3 transitions in Mg-like ions with [formula omitted

Multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) methods are utilized for theoretical calculations of energy levels, wavelengths, line strengths, absorption oscillator strengths, and transition probabilities in 3s2-3s4p, 3s3p-3s4s, 3s3p-3s4d, 3s3p-3p4p, 3s3d-3s4f, 3p2-3p4s, 3p2-3p4d, and 3p3d-3p4f transitions in Mg-like ions with 15≤Z≤30. The calculations of energies account for Breit interaction and quantum electrodynamics (QED) contributions. The active space approximation is employed for the calculations, and energy converges when the active orbital set is increased to n = 7. The calculated lowest 78 levels including valence and core–valence correlations in Mg-like ions with Z=15–30 show good agreement with experiment results and other calculations. The relative difference between calculated wavelengths and experiment values exhibits a decreasing trend as the atomic numbers increase, and the difference is better than 1% for a majority of transitions. To evaluate the accuracy of the wave functions and transition parameters, the quantity dT is analyzed within 0.1 for most strong transitions. The transition probabilities are compared with other theoretical values to analyze with line strength S. Such calculations may provide valuable data for the experimental study of plasma diagnostics and modeling as there are others.

On the temperature dependence of transition intensities of rare-earth ions: A modified Judd-Ofelt theory

We report on a modification of the Judd-Ofelt theory accounting for thermal populations of Stark sub-levels of the multiplets involved in transitions in absorption and emission. The calculations require the data on the crystal-field splitting, the irreducible representations of Stark sub-levels and the selection rules for electric-dipole transitions. Simple formulas for absorption oscillator strengths and probabilities of radiative spontaneous transitions are obtained. The application of the proposed model allowed us to remove the contradiction between the transition intensities in absorption and emission (3H6 ↔ 3F4) for Tm3+-doped crystals. It was also used to explain the experimental temperature dependences of luminescence lifetimes of the 3F4 Tm3+ manifold in two widely used laser crystals, LiYF4 and Y3Al5O12. The case of Yb3+ ions featuring a small number of crystal-field sub-levels is also considered.

Extension of nature's NIR-I chromophore into the NIR-II region.

The development of chromophores that absorb in the near-infrared (NIR) region beyond 1000 nm underpins numerous applications in medical and energy sciences, yet also presents substantial challenges to molecular design and chemical synthesis. Here, the core bacteriochlorin chromophore of nature's NIR absorbers, bacteriochlorophylls, has been adapted and tailored by annulation in an effort to achieve absorption in the NIR-II region. The resulting bacteriochlorin, Phen2,1-BC, contains two annulated naphthalene groups spanning meso,β-positions of the bacteriochlorin and the 1,2-positions of the naphthalene. Phen2,1-BC was prepared via a new synthetic route. Phen2,1-BC is an isomer of previously examined Phen-BC, which differs only in attachment via the 1,8-positions of the naphthalene. Despite identical π-systems, the two bacteriochlorins have distinct spectroscopic and photophysical features. Phen-BC has long-wavelength absorption maximum (912 nm), oscillator strength (1.0), and S1 excited-state lifetime (150 ps) much different than Phen2,1-BC (1292 nm, 0.23, and 0.4 ps, respectively). These two molecules and an analogue with intermediate characteristics bearing annulated phenyl rings have unexpected properties relative to those of non-annulated counterparts. Understanding the distinctions requires extending concepts beyond the four-orbital-model description of tetrapyrrole spectroscopic features. In particular, a reduction in symmetry resulting from annulation results in electronic mixing of x- and y-polarized transitions/states, as well as vibronic coupling that together reduce oscillator strength of the long-wavelength absorption manifold and shorten the S1 excited-state lifetime. Collectively, the results suggest a heuristic for the molecular design of tetrapyrrole chromophores for deep penetration into the relatively unutilized NIR-II region.

Extension of Judd-Ofelt theory: Application on Eu3+, Nd3+ and Er3+

We present a modified version of the Judd-Ofelt theory, which describes the intensities of f-f transitions for trivalent lanthanide ions (Ln3+) in solids. In our model, the properties of the dopant are calculated with well-established atomic-structure techniques, while the influence of the crystal-field potential is described as a perturbation, by three adjustable parameters. Compared to our previous work (Hovhannesyan et al., 2022 [28]), the spin-orbit interaction within the first excited configuration 4fw−15d is described in a perturbative way, whereas it is exactly taken into account in the ground configuration 4fw, using all the eigenvector components of the free-ion levels. Moreover, the wavelength-dependence of the refractive index of the host material is also accounted for. We test the validity of our model on three ions: Eu3+, Nd3+ and Er3+. The results of the extension are satisfactory, we are able to give a physical insight into all the transitions within the ground electronic configuration, and also to reproduce quantitatively experimental absorption oscillator strengths. We also performed calculations of standard JO parameters, and the results are in good agreement with the values reported in the literature. The code used to make the calculations is available on GitLab.

Absorption Line Oscillator Strengths for the C 2Π(0)-A 2Σ+(0) Band of Nitric Oxide

We have determined absorption oscillator strengths for rotational transitions of the C 2Π(0)-A 2Σ+(0) band of NO, which has been detected in the upper atmosphere of Venus. The molecular quantum defect orbital method has been used in the calculation of the electronic transition moment and the Rydberg–valence interaction between the C 2Π(v = 0) and the B 2Π (v = 7) states has been considered. Considerable deviations from normal intensity distribution of the rotational lines have been found at J ≤ 5.5. As far as we know, the present line f-values are reported here for the first time. These data may be useful in the interpretation of the observations obtained by the Visible and Infrared Thermal Imaging Spectrometer instrument on the Venus Express spacecraft.

Exploration of Coumarin Derivative: Experimental and Computational Modeling for Dipole Moment Estimation and Thermal Sensing Application.

The Optical properties of the FBTC (1-((4-((5-chlorobenzo[d]oxazol-2-ylthio)methyl)-1H-1,2,3-triazol-1-yl)methyl)-3H-benzo[f]chromen-3-one) molecule were studied experimentally and theoretically. The spectra of absorption and fluorescence were recorded in various solvents to explore their Solvatochromic behavior and dipole moment at room temperature. To determine the ground and excited state of dipole moment experimentally and theoretically, we employed different Solvatochromic techniques, including microscopic solvent polarity functions developed by Lippert, Bakhshiev, Kawaski-Chamma-Viallet, and Reichardt's, as well as density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The stability of the excited state dipole moment in FBTC is higher. Using prime functional, FBTC was optimized in its ground state, and its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital), energies were estimated. These values were then compared with those obtained through cyclic voltammetry. Based on the HOMO and LUMO values given, we calculated the global reactivity parameter and energy gap, which was found to be low at 3.77eV. This study also includes an estimation of electron absorption energies and oscillator strength. Natural population analysis (NPA), Milliken atomic charge, and molecular electrostatic potential (MESP) map are correlated. In addition, FBTC exhibited exceptional physiological temperature sensing behaviour from 20°C -65°C with high relative sensitivity and firm stability. Hence these results confirm that FBTC is a potential candidate for photonic devices and it's also applicable in optical temperature sensing.

Fully relativistic many-body perturbation energies, transition properties, and lifetimes of lithium-like iron Fe XXIV

Employing the advanced relativistic configuration interaction (RCI) combined with the many-body perturbation theory (RMBPT) method, we report energies and lifetime values for the lowest 35 energy levels from the (1s2)nl configurations (where the principal quantum number n = 2–6 and the angular quantum number l = 0,…,n–1) of lithium-like iron Fe XXIV, as well as complete data on the transition wavelengths, radiative rates, absorption oscillator strengths, and line strengths between the levels. Both the allowed (E1) and forbidden (magnetic dipole M1, magnetic quadrupole M2, and electric quadrupole E2) ones are reported. Through detailed comparisons with previous results, we assess the overall accuracies of present RMBPT results to be likely the most precise ones to date. Configuration interaction effects are found to be very important for the energies and radiative properties for the ion. The present RMBPT results are valuable for spectral line identification, plasma modeling, and diagnosing.

Spectra and excitation properties of (AlP)8: Effect of external electric fields

AbstractOn the basis of density functional theory (DFT), the geometry and infrared spectrum of the (AlP)8 cluster have been calculated under external electric fields (EEFs). In addition, on the basis of time‐dependent DFT, the ultraviolet–visible absorption spectra, oscillator strengths, wavelengths, and hole–electron orbits of the first 20 excited states have been calculated. Under EEFs, the energy of (AlP)8 gradually decreases, the dipole moment increases, and the molecular configuration significantly changes. In the infrared spectrum, the vibration frequency corresponding to the stretching vibration of the Al–P bond decreases, and a red shift occurs. With increasing EEF, the infrared spectrum splits and shows an obvious Stark effect; the ultraviolet absorption intensity is enhanced, and the molecular excitation energy decreases. Additionally, the excitation wavelength increases with increasing EEF. It is conclusively shown that the (AlP)8 cluster is easily excited under an EEF. Separation of the holes and electrons of the (AlP)8 cluster is obvious. Theoretical investigation of the spectra and excitation properties of (AlP)8 is an important step toward a comprehensive understanding of the effects of EEFs on the molecular structure, stability, and dynamics.

Analytical Expressions for the Eigenfunctions and Structural Properties of Hydrogen Atom Under the Screening Effect of Hulthén Potential

Jost solution and Jost function have been exploited to express bound state energies and solutions for Hulthén potential. The derived eigenfunctions are further used to construct analytical expressions for different spectral observables under the screening effect of Hulthén potential. For different dipole transitions, absorption oscillator strength, transition probability, and ground state dipole polarizability are calculated for hydrogen atom with the variation of screening parameter and found in close agreement with available theoretical results.

The Computational Investigation of IR and UV-Vis Spectra of 2-isopropyl-5-methyl-1,4-benzoquinone Using DFT and HF Methods

A theoretical study on the thymoquinone compound has been performed through two theoretical methods, DFT/B3LYP and HF with 6-31G, 6-31G(d, p) and 6-31++G(d, p) basis sets using Gaussian 09 program. Some theoretical properties, like vibrational and electronic properties especially UV-Vis and FT-IR spectra, of the title compound were analyzed and then compared with available experimental data. The calculated harmonic vibrational frequencies have been scaled with standard scaling factors 0.9 and 0.965 for HF and DFT/B3LYP, respectively and then compared with available experimental FT-IR spectrum. Furthermore, the statistical analysis was investigated to evaluate the performance of both the HF and DFT methods, including root mean square error (RMSE), mean absolute error (MAE) and mean percentage error (MPE). According to the assigned vibrational modes of the title compound, it could be concluded that the DFT/B3LYP method with 6-31++G(d, p) basis set had the best agreement with experimental data. UV-Vis absorption spectra, excitation energies, maximum absorption wavelength, electronic transitions and oscillator strengths of the title compound were calculated by time dependent density functional theory ( TD-DFT) method using the same basis set and compared with available experimental data. The results showed the best performer was HF method with 6-31G basis set.

A comparative study on optical properties of AlCl-Pc, AlH-Pc, Al-Pc, and phthalocyanine organic compounds

The role of Cl and H atoms inside AlPc organic molecule by experimental, DFT, and TD-DFT methods is investigated. A detailed study of Pc, AlPc-Cl, and AlH-Pc absorption wavelengths, energies, and oscillator strengths are achieved. To strengthen such investigation, HOMO-LUMO and DOS spectrum analysis are described showing the optical band of 2.01, 2.11, and 2.18 eV for Al-Pc, AlH-Pc, and AlCl-Pc compounds respectively, and nonlinear optical properties are presented. Furthermore, the values of calculated dipole moment, polarizability, and second-order static hyperpolarizability of AlCl-Pc, AlH-Pc, Al-Pc, and Pc compounds are studied. The heterojunctions based on AlPc-Cl and AlPc-H are fabricated by low-cost routes. I-V characteristics are demonstrated under dark and room temperatures. A high rectifying ratio of our heterostructures based on AlPc is exhibited. Non-ideal behavior, [Formula: see text] 1, of the fabricated heterostructures due to the presence of interface states is revealed.

Transition Energies and Line Oscillator Strengths of the C 2Π(0)-X 2Π(0–6) Absorption Bands of Nitric Oxide. A Theoretical Study

Theoretical absorption oscillator strengths and wavelengths for rotational transitions of the C 2Π(v′ = 0)-X 2Π(v″) bands with v″ = 0–6 of nitric oxide are reported. The Molecular Quantum Defect Orbital method has been used in the calculations and the known interaction between the C 2Π(v = 0) Rydberg and the B 2Π (v = 7) valence states has been dealt with through an appropriate rovibronic energy matrix. We hope that the reported data may be useful in the analysis of the observed ultraviolet nightglow emission from nitric oxide in the upper atmospheres of Earth, Venus, and Mars.

Structural, DFT calculations and photophysical and photochemical characteristics of 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) benzene (PPPBB)

X-ray single crystal structure and spectroscopic and photophysical parameters of the titled compound were studied. The titled compound shows thermal stability prior to melting at 126.17 °C with Δ H value of 109.991 J g−1. Photophysical parameters include singlet electronic absorption, molar absorption coefficient, oscillator strength, and dipole moment of electronic transition, fluorescence spectra, excited state lifetime, and fluorescence quantum yield for 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) (PPPBB) in different solvents. PPPBB displays a little change in maximum absorption and emission spectra with solvent polarity, indicating a slight change in dipole moment of dye molecules upon excitation. The dipole moments' (Δ μ) difference between the excited and ground states was obtained from the Lippert–Mataga method. Ground and electronic excited states' geometric optimization was performed using density functional theory (DFT) and time-dependent density functional theory (time dependent-DFT), complemented with spectral findings. A good agreement between theoretical data and experimental observations was found. The net photochemical quantum yield (φc) of PPPBB dye was calculated in various solvents.

Phenothiazine- isophorone dyes (D–π–A and A–π–D–π–A): synthesis, electronic properties and DFT computational study

PurposeThis paper aims to prepare a new donor–π–acceptor (D–π–A) and acceptor–π– D–π–A (A–π–D–π–A) phenothiazine (PTZ) in conjugation with vinyl isophorone (PTZ-1 and PTZ-2) were designed and their molecular shape, electrical structures and characteristics have been explored using the density functional theory (DFT). The results satisfactorily explain that the higher conjugative effect resulted in a smaller high occupied molecular orbital–lowest unoccupied molecular orbital gap (Eg). Both compounds show intramolecular charge transfer (ICT) transitions in the ultraviolet (UV)–visible range, with a bathochromic shift and higher absorption oscillator strength, as determined by DFT calculations.Design/methodology/approachThe produced PTZ-1 and PTZ-2 sensors were characterized using various spectroscopic methods, including Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy (1H/13CNMR). UV–visible absorbance spectra of the generated D–π–A PTZ-1 and A–π–D–π–A PTZ-2 dyes were explored in different solvents of changeable polarities to illustrate positive solvatochromism correlated to intramolecular charge transfer.FindingsThe emission spectra of PTZ-1 and PTZ-2 showed strong solvent-dependent band intensity and wavelength. Stokes shifts were monitored to increase with the increase of the solvent polarity up to 4122 cm−1 for the most polar solvent. Linear energy-solvation relationship was applied to inspect solvent-dependent Stokes shifting. Quantum yield (ф) of PTZ-1 and PTZ-2 was also explored. The maximum UV–visible absorbance wavelengths were detected at 417 and 419 nm, whereas the fluorescence intensity was monitored at 586 and 588 nm.Originality/valueThe PTZ-1 and PTZ-2 dyes leading to colorimetric and emission spectral changes together with a color shift from yellow to red.

Wavelengths, transition rates, weight oscillator strengths and line strengths for He-like to Ne-like cobalt ions

The multi-configuration Dirac–Hartree–Fock (MCDHF) and Relativistic Configuration Interaction (RCI) methods have been used to calculate the wavelengths, transition rates, absorption oscillator strengths, and line strengths for the 2s-3p, 2p-3s, and 2p-3d electric dipole (E1) transitions in He-like to Ne-like cobalt ions. Breit interaction and quantum-electrodynamical (QED) contributions were estimated in extensive RCI calculations. The results are in good agreement with previous experimental and theoretical results. Our calculated wavelengths differ from wavelengths reported in other work mostly by less than 0.78%, with two exceptions, where our results differ by 1.63% and 1.91%, showing good overall confirmation of the accuracy of our results. Most importantly, we have predicted some theoretical data that, will be helpful in some plasma experiments.

Effect of impurity position and electric field on the optical absorption coefficients and oscillator strength in spherical multilayer quantum dot

Effect of impurity position and electric field on the optical absorption coefficients and oscillator strength in spherical multilayer quantum dot

Structural modification on Dimethoxythienothiophene based non-fullerene acceptor molecule for construction of high-performance organic chromophores by employing DFT approach

In this work, with the directive of increasing the power conversion efficiency of organic solar cells, seven new acceptor molecules (N1–N7) have been designed by the end-group modification of A-D-A type reference molecule TTDTC-4F (R). Density functional theory (DFT) based computational methodologies were applied to these structures to calculate different parameters like their planarity, bandgaps, maximum absorption wavelengths, excitation energies, oscillator strengths, light-harvesting efficiencies, electron and hole reorganization energies, binding energies, dipole moments, open-circuit voltage (Voc), and fill factors (FF), etc. All the devised structures showed better results in terms of their shorter bandgaps, redshift in absorption, lower excitation and binding energies, along with reduced reorganization energies, which emphasizes their better charge transfer properties with respect to R. Furthermore, they also demonstrated good values of dipole moment and light-harvesting efficiencies (LHE). Higher LHE values of designed molecules pointed towards their better abilities to harvest light in order to produce charge carriers. But in terms of open-circuit voltage (Voc) and fill factor (FF), N2 and N5 showed higher, while N7 showed the highest result when compared to R. So, these developed molecules could be the best choice for utilization in the active layer of organic solar cells (OSCs).