Electronic Transition Processes Research Articles

A comprehensive study on three typical photoacid generators using photoelectron spectroscopy and abinitio calculations.

Conducting a comprehensive molecular-level evaluation of a photoacid generator (PAG) and its subsequent impact on lithography performance can facilitate the rational design of a promising 193nm photoresist tailored to specific requirements. In this study, we integrated spectroscopy and computational techniques to meticulously investigate the pivotal factors of three prototypical PAG anions, p-toluenesulfonate (pTS-), 2-(trifluoromethyl)benzene-1-sulfonate (TFMBS-), and triflate (TF-), in the lithography process. Our findings reveal a significant redshift in the absorption spectra caused by specific PAG anions, attributed to their involvement in electronic transition processes, thereby enhancing the transparency of the standard PAG cation, triphenylsulfonium (TPS+), particularly at ∼193nm. Furthermore, the electronic stability of PAG anions can be enhanced by solvent effects with varying degrees of strength. We observed the lowest vertical detachment energy of 6.6eV of pTS- in PGMEA solution based on the polarizable continuum model, which prevents anion loss at 193nm lithography. In addition, our findings indicate gas-phase proton affinity values of 316.4 kcal/mol for pTS-, 308.1 kcal/mol for TFMBS-, and 303.2 kcal/mol for TF-, which suggest the increasing acidity strength, yet even the weakest acid pTS- is still stronger than strong acid HBr. The photolysis of TPS+-based PAG, TPS+·pTS-, generated an excited state leading to homolysis bond cleavage with the lowest reaction energy of 83 kcal/mol. Overall, the PAG anion pTS- displayed moderate acidity, possessed the lowest photolysis reaction energy, and demonstrated an appropriate redshift. These properties collectively render it a promising candidate for an effective acid producer.

A 1750nm thulium-doped optical fiber laser design: Theoretical model and code simulation

This article mainly studies the physical model design and code simulation of a thulium-doped fiber laser that outputs 1750nm laser. The optical fiber laser has been widely used due to its excellent performance compared with other solid-state laser devices. Among all types of fiber lasers, ytterbium-doped fiber lasers possess the highest output power, whereas they seem to be impractical when an output laser with a longer wavelength is required. However, Thulium-doped lasers have huge room for development to solve the problem, whose unique center wavelength characteristics provide them with huge utilization value. This article shows the electronic transition process a of thulium-doped laser and the power transmission diagram in the fiber. Its rate equation and power equation are also listed below. Through paper retrieval and data extraction, the values of laser parameters can be accurately confirmed, and its power curve can also be obtained through simulation. After analyzing the data obtained from the simulation, the working principle of the fiber laser was intuitively displayed, and the performance of the system was further evaluated. Last but not least, several limitations of this experiment will also be discussed, in order to explore the system more thoroughly.

Design of the 1650-1700nm U band doped fiber laser

Increasing the power of thulium-doped fiber lasers is an important direction for the future development of fiber lasers. Thulium ions exhibit excellent optical properties in the U-band, making them valuable for research. This paper has established a modular design process for fiber lasers, investigating the energy level system of Thulium ions, electron transition processes, power propagation equations, pump power threshold, laser output power, and Bragg grating reflectance for specific wavelength photons. The reflectance of the front and rear cavity mirrors and Bragg grating was also redesigned. Finally, by establishing a physical model and employing numerical simulations, the relationship between laser onset power and pump light input power was determined: when the pump light input power reaches 10.1W, a population inversion occurs, and the fiber laser begins to generate laser output power. The laser output power linearly increases with the increase in pump light input power. When the pump light input power reaches 100W, the laser output power reaches its maximum value of 14.17W. This provides valuable data support for the laboratory preparation of 1650-1700nm thulium-doped fiber lasers.

Theoretical study on the differences in donor‐acceptor interaction and electron transition mechanism in Pd(II) and Pt(II) complexes

AbstractThe relativistic effect enhances spin‐orbit coupling (SOC), making metal complexes potential candidates for phosphorescent OLED emitters. However, the relativistic effect profoundly influences the donor and acceptor interactions (D‐A), resulting in unique electron transition processes. By stabilizing the s orbitals and destabilizing the d orbitals of the center metal atom, the relativistic effect enhances donation, back donation, and the trans effect in PtN1N more than in PdN1N. Particularly, the back donation in PtN1N is approximately four times greater than that in PdN1N, contributing to the greater stability and rigidity in PtN1N. Furthermore, the relativistic effect enhances the SOC and reduces the excitation energy and stabilizes the excited states of PtN1N. Consequently, the radiative decay rate and non‐radiative rate are accelerated simultaneously. The reverse intersystem crossing rate in PdN1N is accelerated by high temperature, which is responsible for thermally activated delayed fluorescence (TADF).

Broadband and ascendant nonlinear optical properties of the wide bandgap material GaN nanowires

Gallium nitride (GaN) nanowire, as a type of wide bandgap nanomaterial, has attracted considerable interest because of its outstanding physicochemical properties and applications in energy storage and photoelectric devices. In this study, we prepared GaN nanowires via a facile chemical vapor deposition method and investigated their nonlinear absorption responses ranging from ultraviolet to near-infrared in the z-scan technology under irradiation by picosecond laser pulses. The experiment revealed that GaN nanowires exhibit remarkable nonlinear absorption characteristics attributed to their wide bandgap and nanostructure, including saturable absorption and reverse saturable absorption. When compared to bulk GaN crystals, the nanowires provide a richer and more potent set of nonlinear optical effects. Furthermore, we conducted an analysis of the corresponding electronic transition processes associated with photon absorption. Under high peak power density laser excitation, two-photon absorption or three-photon absorption dominate, with maximum modulation depths of 73.6%, 74.9%, 63.1% and 64.3% at 266 nm, 355 nm, 532 nm, and 1064 nm, respectively, corresponding to absorption coefficients of 0.22 cm/GW, 0.28 cm/GW, 0.08 cm/GW, and 2.82 ×10−4 cm3/GW2. At lower peak energy densities, GaN nanowires demonstrate rare and excellent saturation absorption characteristics at wavelength of 355 nm due to interband transitions, while saturable absorption is also observed at 532 nm and 1064 nm due to band tail absorption. The modulation depths are 85.2%, 41.9%, and 13.7% for 355 nm, 532 nm, and 1064 nm, corresponding to saturation intensities of 3.39 GW/cm2, 5.58 GW/cm2 and 14.13 GW/cm2. This indicates that GaN nanowires can be utilized as broadband optical limiters and high-performance pulse laser modulating devices, particularly for scarce ultraviolet optical limiters, and saturable absorbers for ultraviolet and visible lasers. Furthermore, our study demonstrates the application potential of wide bandgap nanomaterials in nonlinear optical devices.

Synthesis, Theoretical and Experimental Investigation of Electronic Properties of New Fluoranthenyl-Based Compounds for OLEDs Applications.

Three novel conjugated molecules have been synthesized: 2-(fluoranthen-3-yliminomethyl)-3,4-ethylenedioxythio-phene (EIF), 2-(fluoranthen-3-yliminomethyl) thiophene (TIF), and 2-(fluoranthen-3-yliminomethyl) fluorene (FIF). Optical properties were obtained from electronic absorption and emission spectra in DMSO solution. The solvatochromic properties of the molecules have been studied in different solvents. Electrochemical properties were studied by cyclic voltammetry in a Bu4NBF4 (0.1 M)/MeCN organic solution. As part of investigations to explain the nature of electronic transition process, we have performed geometry optimization of both the ground and the vertical excitation states, using the DFT B3LYP/6-311G (d, p) and TD-DFT (CPCM)/B3LYP/6-311G (d, p) approaches, respectively. Theoretical calculations closely match the experimental findings. Results show that EIF, TIF and FIF are potential candidates to be used as electron transport layer in Organic Light-Emitting Diodes (OLEDs).

Flux and fluence effects on the vacuum-UV photodesorption and photoprocessing of CO2 ices.

CO2 is a major component of the icy mantles surrounding dust grains in planet and star formation regions. Understanding its photodesorption is crucial for explaining gas phase abundances in the coldest environments of the interstellar medium irradiated by vacuum-UV (VUV) photons. Photodesorption yields determined experimentally from CO2 samples grown at low temperatures (T = 15 K) have been found to be very sensitive to experimental methods and conditions. Several mechanisms have been suggested for explaining the desorption of CO2, O2 and CO from CO2 ices. In the present study, the cross-sections characterizing the dynamics of photodesorption as a function of photon fluence (determined from released molecules in the gas phase) and of ice composition modification (determined in situ in the solid phase) are compared for the first time for different photon flux conditions (from 7.3 × 1012 photon per s cm-2 to 2.2× 1014 photon per s cm-2) using monochromatic synchrotron radiation in the VUV range (on the DESIRS beamline at SOLEIL). This approach reveals that CO and O2 desorptions are decorrelated from that of CO2. CO and O2 photodesorption yields depend on photon flux conditions and can be linked to surface chemistry. In contrast, the photodesorption yield of CO2 is independent of the photon flux conditions and can be linked to bulk ice chemical modification, consistently with indirect desorption induced by an electronic transition (DIET) process.

Temperature dependence of MXenes plasmons induced hot carrier generation and transport

Unlike conventional optoelectronic devices, plasmon-driven optoelectronic devices can efficiently realize energy conversion and regulate the energy distribution of hot carriers through high-energy, non-equilibrium “hot” electron-hole pairs (hot carriers) generated by surface plasmon non-radiative decay, thereby presenting new opportunities for realizing hot carrier optoelectronic devices. As the basis for the practical application of plasmon optoelectronic devices, searching for plasmon metal materials with exceptional performance has always been an important topic in the field of hot carrier optoelectronic devices. Currently, MXenes can be synthesized on a large scale and has excellent photoelectric properties, so it can be used to build a variety of hot carrier photodetectors with unique structures and functions. Unlike the fixed surface ends of two-dimensional materials such as graphene, MoS<sub>2</sub> and borophene, MXenes has an abundance of surface functional groups. However, the increase of ambient temperature will accelerate the oxidation modification of surface functional groups, thus affecting the life and performance stability of optoelectronic devices. In view of the inherent limitations of experimental research on dynamic characteristics of hot carriers at continuous temperatures, we study the temperature effects on the electronic state distributions and scattering effects by using the theory of multi-body perturbation and quantum mechanics. Particularly, we introduce temperature effect into interband electron transition and phonon-assisted electron transition process to obtain temperature dependent dielectric function. From the perspective of non-radiative decay of surface plasmon, we quantify the hot carrier generation efficiency, energy distribution and transport characteristics by first principles calculations, in order to systematically study the ambient temperature dependence of plasmon-induced hot carriers in MXenes. The results show that the interband transition and the phonon-assisted electron transition in MXenes together efficiently produce high-energy hot hole-dominated carriers with a long lifetime and transport distance, which is comparable to borophene. The increase of ambient temperature significantly improves the hot carrier generation efficiency in the infrared range. Meanwhile, the physical mechanism of hot carrier generation in visible light is almost unaffected by the increase of ambient temperature, and the generated hot holes show excellent ambient temperature stability. In addition, the lifetime and transport distance of hot carriers decrease with ambient temperature increasing, which is mainly due to the enhanced scattering of electrons and optical phonons. The research results will provide theoretical and data support for quantitatively evaluating the ambient temperature stability of MXenes plasmon optoelectronic devices in practical environment.

Electronic Structure of Small Isolated and Supported Manganese Oxide Clusters.

In the present work, possible molecular models of the isolated manganese oxides and supported Mn3Ox/Al2O3 structures were built based on small clusters of passivated MnOx. The support was represented as a simplified model of the alumina tetramer cluster based on small fragments of AlOxHy. Combinations of MnOxHy and AlOxHy clusters were made to form both the isolated and supported manganese oxides clusters. The electronic structure of these systems was characterized by ab initio methods (DFT and CASPT2). It was observed that the vertical excitation energy of the isolated and supported Mn3OxHy clusters is significantly lower than that of the alumina cluster model, while both the isolated and supported Mn3OxHy wave function characters are qualitatively similar with respect to the ground state and electronic transition processes, suggesting that the alumina cluster behaves as an inert support, since there is little contribution of this component in the description of the low-lying electronic states. The present study also reports for the first time the spectroscopic parameters of several clusters containing the manganese transition metal atom.

Modeling and numerical simulation optimization for minimizing the gain spectrum of bismuth-doped broadband fiber amplifiers at 1200-1800 nm

Research on optical fiber amplifiers has gotten much more in-depth in recent years as a direct result of the emergence of the information age. The most effective of these materials are optical fibers that have been doped with rare earth elements. Lasers that have gain media composed of rare-earth doped optical fibers find widespread use in fields such as optical communication, medicine, and the processing of materials. For different rare earth ions, especially for bismuth-doped fiber amplifiers, bismuth-doped fiber has a good prospect in fiber amplifiers and lasers due to its unique luminescence characteristics and ultra-wideband near-infrared luminescence of bismuth. Therefore, for bismuth-doped fiber amplifiers, in this paper, the pump wavelength is designed for the signal wavelength range, energy level structure, and electron transition process. The corresponding rate equation and power equation are established. At the same time, the gain spectrum changes with the fiber length and doping concentration are calculated using Matlab programming, and the maximum and minimum gain differences are minimized using Matlab calculations.

Electron transition dynamics in high-order harmonic generation process from H2+

The high-order harmonic generation from [Formula: see text] has been theoretically investigated by numerically solving the two-dimensional time-dependent Schrödinger equation. A sharp minimum can be seen in the harmonic spectrum for larger internuclear distance. Moreover, the electron transition process between the ground state and the first excited state competes with the ionization process at larger internuclear distance, which is the main reason of the spectral minimum. By superposing the static electric field and adjusting the orientation angle [Formula: see text], it is further proved that the electron transition frequency between two lowest electronic states can be decoded by the minimum.

Modeling and numerical simulation of the gain spectrum of Thulium-doped broadband fiber amplifiers

Nowadays, due to the complex signal medium conversion process of semiconductor laser amplifiers, the optical fiber amplifier, which is a new type of all-optical amplifier, is increasingly used in optical fiber communication lines for signal amplification because it can directly perform all-optical amplification of signals and are especially suitable for relay amplification of long-distance optical communications. Our research project is the gain spectrum of the Thulium-doped broadband fiber amplifier. The signal wavelength range is from to . The goal is to obtain the gain spectrum with fiber length variation, doping concentration, and pump power. This paper follows a logical order that presents the introduction, the formulas used in the experiment, and the result and analysis. According to the output wavelength range, energy level structure, and electronic transition process, we designed the pump wavelength and established the rate and power propagation equations. Eventually, gain spectrum with a variation of fiber length, doping concentration, and pump power is available using MATLAB for programming and calculating. With our research achievement, a more efficient optical fiber amplifier is possible to be made in the future.

Controllable crystal form transformation and temperature sensing properties studies of K3Sc0.5Lu0.5F6: Ho3+, Yb3+ with cryolite structure

AbstractIn this work, a method for controllable regulation of crystal form was proposed for the first time and the effects of different crystal forms on the up‐conversion luminescence properties of Ho3+, Yb3+ co‐doped K3Sc0.5Lu0.5F6 (KSLF) phosphors was explored. KSLF:Ho3+, Yb3+ phosphors were synthesized by the high temperature solid‐state reaction method, and X‐ray diffraction (XRD) results illustrate that the compounds can obtain monoclinic phase and cubic phase at different synthesis temperatures. In addition, according to the power‐dependent up‐conversion luminescence (UCL) intensity, the UCL mechanism and the electronic transition process are discussed. Simultaneously, the temperature sensing behavior of the best samples with different crystal forms at different temperatures was studied by fluorescence intensity ratio technique. All the results show that KSLF:Ho3+, Yb3+ phosphors show great application potential in the field of temperature sensing, and the preparation of KSLF:Ho3+, Yb3+ in different crystal forms can provide a reference value for crystal design and growth.

A novel reddish-orange-emitting phosphor Ca3Gd7(PO4)(SiO4)5O2: Sm3+ for white light-emitting diodes

Phosphor is the decisive material in white light-emitting diodes (WLED), affecting light quality. Silica phosphate has good stability, low cost and environmentally friendly features, so it has great application potential. In this paper, a self-activated reddish-orange phosphor Ca3Gd7(PO4)(SiO4)5O2: xSm3+ was prepared by the high-temperature solid-phase method. The phase purity of the sample was verified by X-ray diffraction (XRD). The Rietveld refinement method was used to resolve further the sample structure and the location of the substitution of rare earth ions. The photoluminescence properties were studied in detail using fluorescence spectra, temperature-dependent emission spectra and other characterization methods. The electron transition and energy transfer processes of Gd3+ in Ca3Gd7(PO4)(SiO4)5O2 were analyzed. The fluorescence decay curve of the sample was obtained, which belongs to the double exponential curve, and the decay lifetime depending on the Sm3+ doping concentration was calculated. Furthermore, a WLED device was assembled, and warm white light was obtained, with a spectrum showing characteristic red emission, proving to complement the missing red component of commercial WLEDs. These results indicate that Ca3Gd7(PO4)(SiO4)5O2: xSm3+ phosphor has great potential for application.

Transition of Orbital Electrons by Electromagnetic Waves

An electromagnetic (EM) wave is a form of continuous energy, of which both the frequency and the amplitude are parts, as shown in a recent report. All the facts relating to the photoelectric effect are explained by the new modified EM wave concept. Since the photon concept is not able to explain the intensity effect and the ejection direction clearly, it cannot be used to explain nonlinear optical phenomena clearly. The current understanding of the interaction process between orbital electrons and light may not be realistic. In this work, the electron transition process is explained with the new modified EM wave concept. The orbital electrons of a material rotate circularly by the sinusoidal fields of the EM waves. In this way, the electrons absorb light energy as rotational kinetic energy. During the first rotational cycle, the electrons with large enough radii face different potential barriers in neighboring orbits. Consequently, the electrons’ speed is obstructed, and the electrons move behind their natural places (phase); in other words, the electrons cannot follow the required phase of EM waves. Thus, sufficient energetic electrons are scattered from their orbit. The high-intensity EM waves reach the inner orbits of the targeted atom and transit electrons from different orbits. The light can regenerate through processes with different frequencies. The frequency of the regenerated light can be higher than that of primary light, depending on the energy (frequency and amplitude) of the primary light. The results of previous reports match the prediction of the new concept of EM waves. The new wave concept may be able to explain all photonic behaviors of light clearly.

Highly efficient and facile removal of As(V) from water by using Pb‐MOF with higher stable and fluorescence

Metal–organic framework (MOF) materials are promising adsorbents for removing As(V) from sodium arsenate aqueous solutions, because of their high porosity and functional modulability. Two novel Pb(II) complexes {[Pb2(bcabsa)(μ2‐OH)]}n (Pb (bcabsa)) and {[Pb (Hbcabsa)]·(4,4′‐bpy)(H2O)}n (Pb (bcabsabpy)) (H3bcabsa = 4‐(N,N′‐bis(4‐carboxy benzyl)amino)benzene‐sulfonic acid, 4,4′‐bpy = 4,4′‐bipyridine), were hydrothermally synthesized. Pb (bcabsabpy) was characterized by single‐crystal X‐ray diffraction (SC‐XRD), X‐ray photoelectron spectroscopy (XPS), photoluminescence, powder X‐ray diffraction (XRD), and infrared radiation (IR) before and after the adsorption of As(V). In addition, the capacity of Pb (bcabsabpy) to remove arsenic was also investigated. The experimental results showed that Pb (bcabsabpy) had high stability within pH 4–12 and a relatively high As(V) removal rate (>90%) in the pH range of 4–10. The adsorption kinetics followed the pseudo‐second‐order kinetic model, whereas the adsorption isotherm was in agreement with the Langmuir equation. Pb (bcabsabpy) had a high adsorption capacity of As(V) in an aqueous solution (Qmax of 25.51 mg g−1). The fluorescence mechanism of the H3bcabsa, Pb (bcabsa), and Pb (bcabsabpy) are assigned to π‐π*, n‐π*, and π‐π* electron transition processes, respectively.

Strategies for Improving the Brightness of Aggregation‐Induced Emission Materials at Aggregate Level†

Comprehensive SummaryThe brightness of fluorescent agents directly determines the imaging performance as required. Among various fluorophores, small organic species are promising given its exact purity/composition and excellent processibility. However, chromophores with planar geometry may suffer from the undesirable aggregation‐caused quenching (ACQ) phenomenon. Encouragingly, luminogens showing aggregation‐induced emission (AIE) features are preferable as the aggregates which are the most common used state. In this review, we mainly focus on the strategies employed for boosting the brightness of AIE‐active luminogens (AIEgens). From molecule to morphology levels, approaches that regulate electronic transition processes of the molecule or the packing extent of aggregates in order to confine molecular motion, reduce π‐π stacking, disrupt fluorophore‐water interactions, etc., are presented. In the end, the current challenges and perspectives are briefly discussed. We anticipate that this review will stimulate new insights and more efforts for the advancement of ultrabright AIEgens.

Effects of solvent polarity on the novel excited-state intramolecular thiol proton transfer and photophysical property compared with the oxygen proton transfer

Recently, the dual-fluorescent phenomena of excited state intramolecular thiol proton transfer (ESIPT) for 3-thiolflavone derivative (3NTF) were reported by Chou and coworkers for the first time [J. Am. Chem. Soc. 143 (2021) 12715–12724], which opened a new chapter in the field of ESIPT. Based on density functional theory (DFT) and time-dependent density functional theory (TDDFT), the proton transfer processes of 3NTF in toluene, dichloromethane and acetonitrile were studied. By optimizing the structure of the ground (S0) state and first excited (S1) state of 3NTF in different solvents, the hydrogen-bond parameters and proton-transfer potential energy curves were calculated. It was shown that although photo-excitation enhanced the intramolecular hydrogen bonding strength and thus promoted the occurrence of ESIPT, the solvent polarities inhibited the enhancement of the hydrogen bond of S1 state, which was not conducive to ESIPT. The electron spectra analyses were consistent with experimental data, which confirmed the rationality of molecular configurations. The time-evolved excited state dynamics simulation was performed based on the optimized structure of 3NTF, indicating that the ESIPT was an ultrafast photochemical reaction less than 180 fs. Moreover, we compared the potential energy surfaces of ESIPT, electronic structures based on natural transition orbitals (NTOs) method and electron-hole isosurfaces for the 3NTF and the traditional flavone molecule (3NHF), concluded that the unusually large Stokes shift fluorescence of 3NTF was mainly caused by the coupling of ESIPT and twisting intramolecular charge transfer (TICT), and the 3NTF isomer had the more nπ* character in the electron transition process. The nπ* ICT significantly increased with the decrease of solvent polarities, affecting the molecular photophysical properties, this made it more widely used in biomedical, photochemical, materials science and other fields.

Quantum and semiclassical studies of nonadiabatic electronic transitions between N(4S) and N(2D) by collisions with N2.

The dynamics and kinetics of spin-forbidden transitions between N(2D) and N(4S) via collisions with N2 molecules are investigated using a quantum wave packet (WP) method and the semi-classical coherent switches with decay of mixing (CSDM) method. These electronic transition processes are competing with exchange reaction channels on both the doublet and quartet potential energy surfaces. The WP and CSDM quenching rate coefficients are found in reasonable agreement with each other, and both reproduce the previous theoretical results. For the excitation process, the agreement between the two approaches is dependent on the treatment of the zero-point energy (ZPE) in the product, because the high endoergicity of this process leads to severe violation of the vibrational ZPE. The Gaussian-binning (GB) method is found to improve the agreement with the quantum result. The excitation rate coefficients are found to be two orders of magnitude smaller than that of the adiabatic exchange reaction, underscoring the inefficient intersystem crossing due to the weak spin-orbit coupling between the two spin manifolds of the N3 system.

The Nobel Prize in Physics 2023

The Nobel Prize in Physics was awarded to Pierre Agostini of Ohio State University, Ferenc Krausz of the Max Planck Institute of Quantum Optics and the Ludwig-Maximilian University of Munich and Anne L’Huillier of the Lund University for "experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter". The Prize acknowledges the tremendous experimental progress in the past 35 years that eventually enabled the investigation of the fastest electron transition processes in atoms, molecules and solids by using state-of-the-art femtosecond laser technology. As a result, a new field of research emerged and shortly after the establishment of the field of femtochemistry, attophysics came of age.