Electronic Oscillator Strengths Research Articles

DFT and TD‐DFT Study of Many‐Body and Hydrogen Bonding Interactions: Nitrosamine Oligomers

AbstractThis study focuses on the properties and intermolecular interactions of nitrosamine oligomers, which are important in both semiconductor manufacturing and nuclear waste management. The study explores various configurations of nitrosamine oligomers, ranging from monomers to pentamers in linear, ladder, and cyclic clusters, with the finding that dimer cyclic forms and hexamers and above are unstable. Many‐body analysis revealed that two‐body interaction energies made remarkable contributions to the binding energy, while the sum of 3‐, 4‐, and 5‐body energy contributed less, indicating the decrease in stability of nitrosamine from dimer to pentamer clusters. Using advanced computational techniques, such as dispersion‐corrected B3LYP‐D3 and TD‐DFT, the study investigates the vibrational modes and electronic absorption spectra of nitrosamine oligomers. The results reveal that different configurations can significantly affect the vibrational modes and electronic properties of nitrosamine oligomers. The NH2 symmetric and asymmetric modes were particularly intense in various forms of nitrosamine oligomers. The wavelengths of electronic transition, oscillator strength, and HOMO to LUMO gap were reported. Additionally, the study reports on nitrosamine oligomers’ hydrogen‐bonded cooperativity and binding energy contributions. Overall, these findings offer valuable insights into the stability and properties of nitrosamine oligomers, with potential applications in materials science and chemical engineering.

The solvatochromic effect of functionalized 6-aminoracil derivatives in light of DFT: FT-IR, TD-DFT, NBO, and FMO studies

Uracil-based compounds have increasing attention in material design for different applications as well as pharmaceutical purposes. Accordingly, the key electronic reasons underlying the solvatochromic effect and possible activity features by using quantum chemical computations should be explored in detail. This work focuses on the structural, electronic, and optical properties of the aminouracil derivatives to explore the key electronic-related properties that affect the solvatochromism features. The molecular geometries of the 1,3-dimethyl-5-(arylazo)-6-aminouracil derivatives were optimized using the DFT method at the B3LYP/6–31++G(d,p) basis set level. The solvent-phase simulations of the studied derivatives were utilized using the PCM (Polarized Continuum Model). The TD-DFT approach was employed to enlighten UV–visible characteristics such as possible electronic transitions, energies, and oscillator strengths. The NBO (Natural Bond Orbital) method was used to predict the possible intramolecular charge transfer and delocalization, as well as the interactions between donor-acceptor molecular orbitals. TD-DFT computations revealed that the bonded group within the arylazo ring would affect solvatochromic properties such as electronic excitation energies and transitions in the UV-Vis regions. The NBO analysis revealed that the electron movement from the lone pair of N atoms on the uracil unit to neighbor unfilled orbitals contributed to reducing the stabilization energy.

Shape and quantum size effects on the electronic structure, oscillator strengths and state lifetimes of helium-like quantum dots

Transition energies, electric static polarizability, oscillator strengths and state lifetimes of helium-like quantum dots are determined as a function of their shape and size. A configuration interaction approach based on B-spline functions is used. We found that, the oscillator strengths present an extremum around a low value of the dot radius whatever the shape of the confining potential. This extremum is due to the pressure on the energy levels in such a way that for a particular value of the dot radius, the second electron in the excited one-electron state reaches the borders of the confinement potential. The extremum position depends on the impurity charge and the oscillator strength value at this point changes with the potential well shape. As well, the increase of the effective mass involves the shift of the position of the oscillator strength extremum towards weak radius values. The first excited state lifetime globally increases with the dot radius and the reduction of the nuclear charge but presents a shoulder for a certain low value of the dot radius mostly marked for a triangular form of the confining potential.

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.

Pressure Engineering Toward Harvesting the Bright Deep‐Blue‐Light Emission in Y‐based Metal‐Organic Frameworks

AbstractThe emergence of metal‐organic frameworks (MOFs) provides a new platform of low‐cost and color‐saturated blue light‐emitting diodes ideal for display and solid‐state lighting applications. However, numerous established MOFs still exhibit weak deep‐blue‐light emission (<450 nm) owing to low energy/charge transfer efficiency. Here a pressure‐treated strategy to greatly enhance photoluminescence performance of deep‐blue light‐emitting Y(BTC)(H2O)6 (H3BTC: benzene‐1,3,5‐tricarboxylic acid) is reported. Pressure‐treated Y(BTC)(H2O)6 exhibits a bright emission at 409 nm with a photoluminescence quantum yield from the initial 2.8% increasing to 75.0%. The hydrogen bonding cooperativity effect increases hydrogen bond binding energy after pressure treatment and thus the planarization structure is locked. The increased electronic transition diversity and oscillator strength originating from the planarization structure are highly responsible for boosting metal‐to‐ligand charge transfer. The findings in this study provide significant insights into the underlying mechanism of the structure‐property relationship in Y(BTC)(H2O)6 and offer a promising strategy to harvest deep‐blue‐emitting MOFs materials.

Shape and Quantum Size Effects on the Electronic Structure, Oscillator Strengths and State Lifetimes of Helium and Helium-Like Dots

Shape and Quantum Size Effects on the Electronic Structure, Oscillator Strengths and State Lifetimes of Helium and Helium-Like Dots

Single and double electron excitation transition rates and oscillator strengths calculations in the study of the x-ray absorption spectrum of Neon

We report a new study of the x-ray absorption spectrum of Neon near the K-edge and near the KL-edge. The study is performed by calculating the transition probabilities and oscillator strengths for excitations from the ground state to singly and doubly excited states, the calculations were performed using multi-configurational Dirac-Fock (MCDF) method. Breit interaction between electrons and finite nuclear size effects were taken into account during the calculations, the transition probabilities were convoluted into Lorentzian line shape profiles. The results of the calculations were then compared to previous measurements of the x-ray absorption spectrum of Neon, good agreement was observed and many features in the spectrum were explained.

Many-body analysis and spectroscopic characterization of diazene oligomers: A theoretical study

The present study reports the many-body analysis and spectroscopic characterization of linear and cyclic diazene oligomers in gas and water solvent states. The oligomers of diazene from monomer to pentamer have been considered for the study. The spectroscopic studies such as geometrical parameters, infrared spectra, electronic absorption spectra, and natural transition orbitals (NTOs) were reported. Many-body analysis techniques have been implemented to study the interactions among the diazene oligomers. These calculations have been performed using exchange and correlation functional (B3LYP) and 6–311++G (d,p) basis set. The geometrical parameters and infrared modes of monomer diazene in the gas state are well-matched with the available experimental determinations at this level of theory. A significant change in vibrational modes of linear and cyclic diazene oligomers has been observed in the gas phase-to-water solvent state. The time-dependent density functional theory (TD-DFT) has been used to calculate the electronic absorption spectra of diazene oligomers. The Wavelength of electronic transitions, oscillator strength, and HOMO to LUMO gap has been reported. Many-body analysis shows that two-, three-, four-, and five-body energies have a remarkable contribution to the binding energy in addition to relaxation energies. All these calculations have been performed using Gaussian 16 program package.

Electronic Terms and Oscillator Strengths of ArXe+ and KrXe+ Molecular Cations

Electronic Terms and Oscillator Strengths of ArXe+ and KrXe+ Molecular Cations

On the effective temperature of large sunspot umbra using AlH molecular lines

In this work, the radiative transition parameters including Franck–Condon (FC) factors, r-centroids, electronic transition moment, Einstein coefficients, band strength, oscillator strength, lifetime and effective vibrational temperature have been computed for A1Π−X1Σ+ and C1Σ+−A1Π systems of aluminium monohydride (AlH) molecule by the numerical integration method for the experimentally known vibrational levels using Rydberg – Klein – Rees (RKR) potential. The computed radiative transition parameters are tabulated. A significant number of well resolved AlH molecular rotational lines of A1Π−X1Σ+ (0,0), (1,1) and (0,1) bands are identified in the sunspot umbral spectrum and the estimated effective rotational temperature has been determined as 2315 K, 2155 K and 1838 K respectively. The effective vibrational temperatures of the A1Π−X1Σ+ and C1Σ+−A1Π systems are found to be 5682 K and 3472 K respectively. Hence, the radiative transition parameters and the effective temperatures confirm the presence of AlH molecule in sunspot spectra.

Impurity effect on the spectral parameters of an electron in a quantum dot–quantum ring semiconductor nanostructure

In the model of effective masses and rectangular potentials, the effect of a hydrogen-like donor impurity on the energy spectrum, electron wave functions and oscillator strengths of intraband quantum transitions in a quantum dot–quantum ring semiconductor nanostructure (GaAs/AlxGa1-xAs) is studied theoretically. The stationary Schrödinger equation for an electron interacting with an impurity cannot be solved analytically exactly. For its approximate solution, the unknown wave functions are sought in the form of an expansion over a complete set of cylindrically symmetric wave functions in the nanostructure without impurity, and the electron energy is found by solving the corresponding secular equation. The dependences of the energy spectrum, the binding energy of the electron with the impurity and the oscillator strengths of the quantum intraband transitions on the geometric parameters of the nanostructure are analyzed.

Synthesis, antibacterial and computational studies of Halo Chalcone hybrids from 1-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)ethan-1-one

In an endeavor to develop antibacterial agents, a series of six 1,4-benzodioxan-6-yl substituted chalcone derivatives were synthesized by the base-catalyzed Claisen-Schmidt reaction of the 1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)ethan-1-one with fluoro and chloro substituted aromatic aldehydes. The synthesized products were characterized by FT-IR, 1H NMR, and 13C NMR spectroscopic techniques. The density functional theory (DFT) calculations were performed using the B3LYP functional with the 6-31G(d,p) basis set for the optimization of molecular geometries and frequency calculations. The CAM-B3LYP functional with a 6-31G(d,p) basis set was used in time-dependent density functional theory (TD-DFT) calculations for the electronic absorption studies. Optimized geometries, frontier molecular orbitals, and global reactivity descriptors' specifications were computed and addressed. The simulated electronic absorption spectra were recorded in the gas phase and dichloromethane (DCM) solvent. The electronic configurations, oscillator strengths, and excited state energies were also discussed. The theoretical UV–Vis and IR vibrational analyses were equated with the experimental findings for the assignment of absorption bands. The synthesized chalcones were evaluated for in vitro antibacterial activities against two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram negative bacteria (Escherichiacoli and Proteus vulgaris). The DFT simulations were correlated with the antibacterial findings and it was discovered that they were highly helpful in the designing antibacterial agents and to establish the structure–activity relationship. Theoretical calculations are in good correlation with the in vitro antibacterial results.

Hydrogen-bonded cluster of nitroxyl: many-body analysis and spectroscopic characterization

Hydrogen bonding interactions in linear and cyclic clusters of nitroxyl are studied using density functional theory at PBEPBE/aug-cc-pvdz level. Many-body analysis technique is used to study the nature and strength of interactions in dimer, trimer, and tetramer of nitroxyl clusters. The vibrational and electronic absorption spectra are also obtained. Calculated geometrical parameters and vibrational frequencies of nitroxyl monomer at PBEPBE/aug-cc-pvdz level are in agreement with the experimental determinations. Significant shift in vibrational frequencies and change in their intensities is observed as we go from monomer to tetramer. Wavelength of electronic transition, oscillator strength, and HOMO to LUMO gap for the nitroxyl clusters are reported from electronic absorption spectra obtained using time-dependent density functional theory. Many-body analysis shows that two-, three-, and four-body energies have significant contribution to the binding energy of nitroxyl tetramers.

Quantum chemical insight into molecular structure, spectroscopic and nonlinear optical studies on methylene bis(dithiobenzoate)-=SUP=-*-=/SUP=-

In this study, the methylene bis(dithiobenzoate) molecule, (C15H12S4), as a bioactive molecule has been subjected to quantum chemical computations using density functional theory (DFT) in order to investigate the molecular geometry, IR, UV-visible and NMR spectral studies. The title molecule has been optimized at the B3LYP, B3PW91 and PBE11PBE levels of DFT and 6-311G(d,p) basis set. Furthermore, the vibrational frequencies, the HOMO-LUMO energy levels, the 1H and 13C NMR chemical shifts (ppm), nonlinear optical properties calculations of the title compound were obtained by B3LYP, B3PW91 and PBE1PBE levels. The maximum electronic transition wavelengths, oscillator strengths, excited state and transition dipole moments for the title compound were also investigated by B3LYP, B3PW91 and PBE1PBE levels of time-dependent (TD)-DFT. Keywords: methylene bis(dithiobenzonoate), IR and UV-vis spectroscopy, 1H and 13C NMR chemical shifts, NLO DFT method.

Spectator electron effects on the two-electron one-photon radiative transition process of double K hole state of Xe[formula omitted] ion([formula omitted

The double electron E1 transition energies, probabilities, and oscillator strengths between the 2s2pn and 1s22pn−1(1≤n≤6) configurations of Xeq+(47≤q≤52) ions with different spectator electrons have been calculated based on the multi-configuration Dirac-Hartree-Fock method. A reasonable electron correlation model is constructed with the aid of the active space method. The finite mass of nuclear, Breit interaction and QED effects have also been included. The calculated results are in good agreement with the available data. The theoretical spectra of different spectator electrons of the double K hole state have been predicted. The spectator electron effects on the transition spectra have been analyzed in detail. The present results will be helpful for analyzing the high energy X-ray spectrum observed from the interaction between high energy highly charged ions and the surface.

Molecular structure, spectral (FT-IR, FT-Raman, Uv-Vis, and fluorescent) properties and quantum chemical analyses of azomethine derivative of 4-aminoantipyrine

A detail of the theoretical study on the molecular geometry and the infrared vibrational frequency assignments of (E)-4-(2-methoxybenzylideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (MBA-dMPP), a bioactive azomethine analog of antipyrine, have been reported and compared with the experimental results. The ground state optimized structure, torsional energies, vibrational wavenumbers, atomic charge analysis, molecular electrostatic potential (MEP) distributions, and energies and maps of frontier molecular orbitals (FMOs) of MBA-dMPP was analyzed using Density Functional Theory (DFT)-B3LYP/6-311G method. Potential energy surface (PES) scans showed that the ground state optimized geometry of MBA-dMPP possesses less torsional energy than that of the crystal structure. Mulliken atomic charge and MEP analyses were carried out to locate the donor-acceptor atoms and reactive sites in the molecule. Calculated quantum chemical descriptors and HOMO-LUMO energies described the molecular properties and reactivity of the studied molecule. We have also calculated average local ionization energy (ALIE) surfaces and Fukui functions to obtain the initial information for the nucleophilic and electrophilic reaction sites of the molecule. Time Dependent (TD)-DFT method was used to calculate electronic transition energy, wavelength, and oscillator strength of MBA-dMPP and to be compared with experimental UV-Vis spectra. The charge transfer mechanism within the molecule is also studied using TD-DFT/B3LYP-/6-311G approach. The fluorescence spectra of MBA-dMPP showed good Stokes shift properties.

Nonlinear optical properties and spectroscopic characterization of Y-shaped polymer using quantum chemical approach.

The present study reports nonlinear optical properties such as the first and second hyper polarizabilities (β and γ) of Y-shaped polymer (P1) and substituted polymers. The basic Y-shaped polymer (R = R1 = H) was named as P1. Upon substitution of one OCH3 group in ortho position of oxygen, it becomes polymer P2 (R1 = H, R = OCH3) and other OCH3 group on another ortho becomes P3 (R1 = R = OCH3). We have also reported structural parameters, vibrational and electronic absorption spectra of polymer, and its substituted polymers. The geometrical parameters such as dipole moment, bond length, and angles are reported at B3LYP/6-311++g** level of theory. In addition, the vibrational, electronic absorption spectra and nonlinear optical (NLO) properties are also reported at the same level of theory. There is a significant change in dipole moment and in energy observed whereas symmetry, bond length, and angles are resembling Y-shaped and substituted polymer. The vibrational spectra of Y-shaped polymer (P1) having the intense peak are C-H stretching mode observed at 1258cm-1. These theoretical vibrational modes are well matching with available experimental determinations. The method dependent hyperpolarizabilities calculated by applying the field along the X, Y, and Z direction. This study confirms the polymer P1 and P2 showing first and second hyperpolarizability response whereas P3 do not show. The electronic absorption spectra for polymer and substituted polymers are also reported at the same level of theory using (TDDFT) approach. The wavelength of electronic transition, oscillator strength, and HOMO-LUMO gap was also reported.

Investigation of physical and spectroscopic properties of WO3 doped zinc-lithium-dysprosium borotellurite glasses

Abstract A set of WO3 doped zinc-lithium-dysprosium-borotellurite glasses in the compositions, (B2O3)0.2–(TeO2)0.3-x–(ZnO)0.28 –(Li2CO3)0.2 –(Dy2O3)0.02–(WO3)x; x = 0.02 to 0.12 (labeled as W1, W2, W3, W4, W5 and W6 respectively) have been synthesized. Amorphous nature of the samples has been confirmed and density measured. Molar volume, oxygen packing density and field strength were determined. Optical absorption spectra were recorded. Band gap values are found to increase with WO3 content up to 0.08 mol fractions and decreases for further amounts of WO3. Urbach energy behaved in the opposite fashion to that of band gap with WO3 content. These results are attributed to bonding defects and the number of non-bridging oxygen. Refractive index, molar refractivity, molar electronic polarizability, reflection loss, metallization ratio, oscillator strengths and Judd-Ofelt (J-O) intensity parameters have been determined. Based on the observed trends of JO intensity parameters, lasing ability of the glasses and their optical quality has been discussed. Photoluminescence (PL) spectra have been recorded and they exhibited three bands namely, 4F9/2 → 6H15/2 (blue), 6H13/2 (yellow) and 6H11/2 (red). The observed ratio of intensity of yellow to blue band inferred that asymmetry around rare earth ions decreases with increase of WO3 content. Using PL decay profiles, the lifetime (τexp) for yellow emission has been determined. Using the values of τexp and estimated radiative lifetime (τR), the quantum efficiency (η) has been determined and for 4F9/2 → 6H13/2 transition and, it is found to be in the range from 43% to 67% for the present glasses. Based on JO parameters, quantum efficiency and other radiative parameters, W4 glass is proposed for lasing in yellow region. For the first time, effect of WO3 on the optical properties of zinc-lithium-dysprosium-borotellurite glasses has been thoroughly investigated.

Electrostatic Field-Induced Oscillator Strength Focusing in Molecules.

The development of light-harvesting devices based on molecular materials depends critically on the ability to focus the electronic oscillator strength of molecules into the UV-vis spectral window. Typical molecular chromophores have only about 1% of their total electronic oscillator strength in this spectral region and thus perform at a small fraction of their possible effectiveness. This theoretical study finds that the electronic oscillator strength of polyenes in the UV-vis region may be enhanced by 1 order of magnitude using electrostatic fields, motivating specific experimental studies of oscillator strength focusing. We find scaling relationships between the polyene length, the intensity of the applied field, and the field-induced increase in oscillator strength that are useful for the implementation of light-harvesting strategies based on polyenes.

Room-Temperature Cavity Ring-Down Spectroscopy of Methylallyl Peroxy Radicals.

We report room-temperature cavity ring-down (CRD) spectra of the à ← X̃ electronic transition of 1-, 2-, and 3-methylallyl peroxy (MAOO•) radicals produced by 193 nm photolysis of methyl-substituted allyl chlorides in the presence of O2. Vibronic structure of experimentally observed spectra was simulated using calculated relative populations of MAOO• conformers, their electronic transition frequencies and oscillator strengths, as well as their vibrational frequencies and Franck-Condon factors of the à ← X̃ electronic transition. The reaction intermediate for the production of 1- and 3-MAOO• radicals, CH3CHCHCH2, is a resonance-stabilized free radical. CRD spectra of 1- and 3-MAOO• radicals obtained using different precursors suggest that allylic rearrangement between the two resonance structures (CH3CH=CHCH2• and CH3CH•CH=CH2) is significantly faster than oxygen addition. Branching ratio between terminal and nonterminal oxygen addition was predicted to be 52:48 on the basis of calculated spin densities, which agrees qualitatively with the experimental CRD spectra of 1- and 3-MAOO• radicals.