Transition Moment Research Articles

Negotiating authenticity: experiences of student influencers on social media

ABSTRACT Research has shown that contemporary youth face a variety of challenges, ranging from social belonging to striving towards perfection in body image and personal achievements in all areas of life. Student life is expected to add further complexities, reflected in a need to negotiate new social connections, spatial environments and academic and future-oriented challenges. This project engaged with a unique and hard-to-reach group of students who define themselves and are defined by others as social media influencers. The objective was to explore the ways in which the participants’ experiences of the influencer marketing industry and its pressures for authenticity intersect with the experiences of being a student. The article draws on 13 in-depth interviews with UK-based student influencers with profiles on different platforms (including TikTok, Instagram, YouTube and the Little Red Book) and discusses how these students navigate the increasingly complex field of monetisation of their content, while maintaining a sense of authenticity and success as a student. It reveals the moments of transition encountered by students when constructing oneself as a successful student who produces content that has strong educational value, and the intricate processes entailed in preserving one’s brand on social media platforms.

Effect of locally excited state on fluorescence transition dipole moment in quadrupolar molecules subjected to symmetry breaking charge transfer.

In excited centrosymmetric donor-acceptor triads of type A-D-A or D-A-D, symmetry breaking charge transfer (SBCT) in polar media has been explored for a few decades. SBCT is accompanied by significant reorganization of the electronic structure of the molecule, which leads to a change in the fluorescence transition dipole moment (TDM). Previously, experiments revealed a 20%-30% reduction in TDM, which occurs on the timescale of SBCT. Simple SBCT models explain this reduction. Here, the effect of the interaction of a locally excited state with zwitterionic states on TDM is investigated. This interaction is shown to have a drastic impact on the TDM and its dependence on the solvent polarity. The magnitude of TDM can decrease monotonically, increase monotonically, and also pass through a maximum with an increase in the SBCT degree due to the locally excited state effect. The scale of changes in TDM in the course of SBCT increases greatly. The conditions for the implementation of a particular scenario have been determined. This work clearly demonstrates the observable influence of upper excited states on the photochemistry and photophysics of molecules. Methods for controlling the fluorescent characteristics of quadrupolar molecules are proposed.

Polariton-assisted incoherent to coherent excitation energy transfer between colloidal nanocrystal quantum dots.

We explore the dynamics of energy transfer between two nanocrystal quantum dots placed within an optical microcavity. By adjusting the coupling strength between the cavity photon mode and the quantum dots, we have the capacity to fine-tune the effective coupling between the donor and acceptor. Introducing a non-adiabatic parameter, γ, governed by the coupling to the cavity mode, we demonstrate the system's capability to shift from the overdamped Förster regime (γ ≪ 1) to an underdamped coherent regime (γ ≫ 1). In the latter regime, characterized by swift energy transfer rates, the dynamics are influenced by decoherence time. To illustrate this, we study the exciton energy transfer dynamics between two closely positioned CdSe/CdS core/shell quantum dots with sizes and separations relevant to experimental conditions. Employing an atomistic approach, we calculate the excitonic level arrangement, exciton-phonon interactions, and transition dipole moments of the quantum dots within the microcavity. These parameters are then utilized to define a model Hamiltonian. Subsequently, we apply a generalized non-Markovian quantum Redfield equation to delineate the dynamics within the polaritonic framework.

Fluorescence scattering under the Stokes–Mueller formalism determines the orientational distribution of fluorophores and the nature of optically active biological proteins

Abstract In the current paper, we represent intrinsic fluorescence anisotropies as four-dimensional normalized Stokes vectors defined by the maximum excitation and emission in the fluorescence process with respect to linear, linear-45 and circular polarizations of light. Depending upon the transition moments for absorption/excitation and emission of fluorophores, eight types of these Stokes vectors can be realized from the Mueller fluorescence matrix of the system. These Stokes vectors probe the orientational distribution of fluorophores and predict the nature of optically active biological proteins, whether laevorotatory or dextrorotatory. The orthogonality relation between the Stokes vectors corresponding to the excitation and emission processes of fluorescence connects the molecular ground and excited states of biological and non-biological systems.

Theoretical study on the spectroscopic and transition properties of phosphorus dimer cation

The potential energy curves of 18 Λ-S states of the P2 + cation have been constructed using the internally contracted multi-reference configuration interaction approach combined with the Davidson correction. The basis-set extrapolation to the complete basis set limit is performed. The relativistic effect is considered in calculations. Treatment of scalar relativistic effect at the third-order Dkroll-Hess approximate and spin-orbit coupling with the state-average Breit-Pauli operator is made. Based on the obtained potential energy curves, the spectroscopic parameters for all bound Λ-S and Ω states are determined. These results are in agreement with experiment where the spectroscopic data are available. The transition dipole moments are calculated. The properties of the dipole-allowed transitions among doublet or quartet Λ-S states are evaluated, from which Einstein coefficients, Franck-Condon factors and radiative lifetimes are estimated. The spin-orbit coupling effect on the transition properties of the 12Πg→X2Πu system is also studied. The spectroscopic and transition properties reported in this study can be used to guide the detection of phosphorus dimer cation in spectroscopy experiments.

Theoretical spin-orbit laser cooling for AlZn molecule.

A spin-orbit coupling electronic structure study of the AlZn molecule is conducted to investigate the molecular properties of the low-lying electronic states and their feasibility toward direct laser cooling. This study uses the complete active-space self-consistent field level of theory, followed by the multireference configuration interaction method with Davidson correction (+Q). The potential energy and dipole moment curves and the spectroscopic constants are computed for the low-lying doublet and quartet electronic states in the 2S+1Λ± and Ω(±) representations. The transition dipole moments, the Franck-Condon factors, the Einstein coefficient, the radiative lifetimes, the vibrational branching ratio, and the slowing distance are determined between the lowest spin-orbit bound electronic states. These results show that the molecule AlZn has a high potential for laser cooling through the X2Π1/2 → (2)2Π1/2 transition by utilizing four lasers at a wavelength in the ultraviolet region, reaching a sub-microkelvin temperature limit.

Thermal experiment study on the self-luminous properties of metallic iron during solid–liquid phase transition

According to the thermal experiment study of the self-luminescence spectrum of industrially pure iron (DT8) at a heating and cooling rate of 5 °C/min, at the moment of 0 (800 °C), DT8 had no significant self-luminescence characteristics in the wavelength range of 200–1100 nm. At the same time, the first-order differentiation of the spectral intensity versus time was equal to zero at the beginning and end moments of the solid-liquid phase transition. When the solid-liquid melt temperatures are equal (i.e. 1531 °C), there are two sharp peaks at wavelengths of 589.1 nm and 766.7 nm of the self-luminous spectrum in the pure liquid state compared to the self-luminous spectrum in the pure solid state. The intensity of the spectrum decreases significantly as the metallic iron changes from the pure solid phase to the pure liquid phase, with a reduction rate greater than 20%. The appearance of the fitted peaks at 589.1 nm and 769 nm was found by XPS fitting analysis to be a significant feature of the difference in the auto-luminescence spectra of pure solid phase and pure liquid phase metallic iron at a constant melt pool temperature. After the transformation of pure solid phase into pure liquid phase, the decay rate of the self-luminous spectrum in the long-wave direction at wavelengths greater than 762 nm is greater than that in the short-wave direction at wavelengths less than 625 nm.

A Chiral Propeller‐Shaped Triple Helicene Shows Multi‐Resonant Thermally Activated Delayed Fluorescence

Multi‐resonant thermally activated delayed fluorescence (MR‐TADF) helicenes show great potential as chiral emitters due to their typically high photoluminescence quantum yield and that they emit circularly polarized luminescence. Here, a new propeller‐shaped chiral MR‐TADF helicene DiKTa3, integrating three DiKTa moieties, was designed and synthesized aiming to achieve co‐parallel electronic and magnitude transition dipole moments that would lead to a high dissymmetry factor, g. It emits at λPL of 491 nm, with a full width at half maximum of 52 nm and has a moderate ΔEST value of 0.24 eV in toluene. The separated (P,P,P) enantiomer shows an absorption dissymmetry factor |gabs| of 6.8 × 10‐4 at 450 nm, which results from a lower symmetry conformation adopted by the compound in solution than the C3‐symmetric optimized structure. This work highlights the strong influence that geometry can have on the chiroptical properties of the emitter.

Photochemistry with Plane-Polarized Light: Controlling Selectivity of a Photochemical Rearrangement.

Over the past 50 years, a principal approach to controlling conventional photochemical reactions has relied on imposing geometric constraints on reactant or transition state via conducting photochemistry in the organized or constraining media. Herein, we describe a fundamentally different approach to affect the course of photochemical reactions (photochemical rearrangements) by utilizing spatially selective excitation of specific electronic transitions with plane-polarized light in the reactant molecules uniformly aligned in the nematic liquid crystal phase. In particular, we focused on the Type B enone rearrangement of 4,4-diarylcyclohexenones -one of the most common photochemical rearrangements. We demonstrated that the aryl migratory aptitude in this reaction was attenuated in response to changing an angle between the polarization plane of the incident light and the alignment direction of nematic liquid crystal, with the enhanced aryl migration achieved when the polarization plane coincided with the transition dipole moment leading to the excited state responsible for this migration. The spatially-selective initial excitation therefore was overruling the electronic factors responsible for the relative ratio of the two alternative photoproducts. The experimental findings were further supported by the results of a computational study. This work showcases a new fundamental paradigm in controlling photochemical reactivity and selectivity of photoreactions.

Coherence Programming for Efficient Linearly Polarized Perovskite Light-Emitting Diodes.

Although quasi-two-dimensional (quasi-2D) perovskites are ideal material platforms for highly efficient linearly polarized electroluminescence owing to their anisotropic crystal structures, so far, there has been no practical implementation of these materials for the demonstration of linearly polarized perovskite light-emitting diodes (LP-PeLEDs). This scarcity is due to difficulty in orientation and phase distribution control of the quasi-2D perovskites while minimizing the defects, all of which are required to manifest aligned transition dipole moments (TDMs). To achieve this multifaceted goal, herein, we introduce a synergistic strategy to quasi-2D perovskites by incorporating both a trimethylolpropane triacrylate anchoring layer and 18-Crown-6 molecular passivator into the film fabrication process. It is found that the interfacial anchoring layer guides the oriented growth of perovskites along the (110) plane, whereas the molecular passivator reduces the number of defects and homogenizes the crystal phase. As a result, a quasi-2D perovskite film with macroscopically aligned TDM that renders high radiative recombination and the degree of linear polarization (DoLP) is constructed. This "coherence-programmed emission layer" demonstrates highly efficient LP-PeLEDs, not only achieving a maximum external quantum efficiency of ∼23.7%, a brightness of ∼36,142 cd/m2, and a DoLP of ∼38%, but also significantly improving the signal-to-interference-and-noise ratio in a multi-cell visible light communication system.

Lowering of the singlet-triplet energy gap via intramolecular exciton-exciton coupling

Organic dyes typically have electronically excited states of both singlet and triplet multiplicity. Controlling the energy difference between these states is a key factor for making efficient organic light emitting diodes and triplet sensitizers, which fulfill essential functions in chemistry, physics, and medicine. Here, we propose a strategy to shift the singlet excited state of a known sensitizer to lower energies without shifting the energy of the triplet state, thus without compromising the ability of the sensitizer to do work. We covalently connect two to four sensitizers in such a way that their transition dipole moments are aligned in a head-to-tail fashion, but, through steric encumbrance, the delocalization is minimized between each moiety. Exciton coupling between the singlet excited states considerably lowers the first excited singlet state energy. However, the energy of the lowest triplet excited state is unperturbed because the exciton coupling strength depends on the magnitude of the transition dipole moments, which for triplets are very small. We expect that the presented strategy of designed intramolecular exciton coupling will be a useful concept in the design of both photosensitizers and emitters for organic light emitting diodes as both benefits from a small singlet-triplet energy gap.

Mourning and orienting to the future in a liminal occasion: (Re)defining British national identity after Queen Elizabeth II's death.

In this paper, we conceptualize the days of mourning that followed the passing of Queen Elizabeth II. as constituting a liminal occasion, a moment of in-betweenness through which we can explore sense-making in times of transition. How do people navigate through liminal occasions, and are they always transformative? Through a rapid response ethnography (Ninterviews = 64, Nparticipants = 122), we were able to capture the raw moments within which a collective comes together, as part of a national ritual, to transition from 'here' to 'there'. In our data, liminality prompted participants to strategically define British national identity and its future by positioning the Queen as representative of Britishness, her loss as a national identity loss. No longer taken for granted, participants reasserted the value of the monarchy as an apolitical and unifying feature in an otherwise divided society, characterizing the continuity of the institution as an essential part of British identity and society. The analysis illustrates how liminality offers a useful conceptual tool for addressing how temporality and change are negotiated in relation to a shared identity, and how navigating transitional moments brings with it political implications for the future.

The A2Π–X2Σ+ Band System of YO

YO bands are conspicuous in the spectra of S stars. The laboratory spectrum of the A2Π–X2Σ+ electronic transition has been recorded with a Fourier transform spectrometer using a composite-wall hollow cathode lamp source. The A2Π–X2Σ+ transition with v′≤4 and v″ ≤ 4 has been rotationally analyzed using the modern spectral fitting program PGOPHER. Vibronic band strengths were calculated using an ab initio transition dipole moment function. A line list for the A2Π–X2Σ+ transition is provided and can be utilized in the modeling of S stars.

Net emission coefficient of magnesium oxide crystal arc plasma with different Mg particle concentrations

The aim of the present study was to construct a molecular spectral database of magnesium oxide crystal arc plasma, thereby allowing for the net emission coefficient of arc to be calculated at different temperatures, pressures and Mg ratios. First, Rydberg-Klein-Rees inversion method was adopted to reconstruct the potential-energy curves of diatomic molecules. Subsequently, the Schrödinger equation was solved to determine the molecular wave function. This solution combined with the electrical transition moment function facilitates the calculation of radiative transition probabilities between different energy levels and the development of this database. Second, calculation models of the bound-free and free-free radiative absorption cross-section were established and use to calculate the continuous radiation of atoms. Finally, the radiative capability of different particles was calculated separately, followed by calculation of the net emission coefficient of plasma through addition The experimental results reveal that the net emission coefficient of air plasma under atmospheric pressure is consistent with existing research in both its magnitude and trend. Given that Mg can be ionized at lower temperatures, the magnesium oxide crystal arc plasma exhibited a pronounced radiative capacity at these temperatures. Additionally, a larger optical transmission distance corresponded to a reduced net emission coefficient of the plasma.

Cavity ring-down spectroscopy of 14N216O near 0.83 µm

The cavity ring-down spectra (CRDS) of nitrous oxide were recorded at a pressure of 10 hPa in the 11,937–12,223 cm-1 range with a threshold sensitivity to absorption coefficient of the order of 6.5 × 10–11 cm-1. Three bands (ν1+5ν3, 6ν1+2ν3, and 3ν1+4ν3) were detected. The line centers and intensities were recovered from the observed spectra. The spectroscopic constants of the upper vibrational states and the vibrational transition dipole moment parameters were fitted to the measured line positions and intensities, respectively. It was found that the 3ν1+4ν3 band is in the interpolyad Coriolis resonance interaction with the 7ν1+7ν21 band. This interaction leads to the appearance in the spectra of the four extra lines of the 7ν1+7ν21 band.

Electronic Spectrum of α-Hydrofulvenyl Radical (C6H7), and a Simple and Accurate Recipe for Predicting Adiabatic Ionization Energies of Resonance-Stabilized Hydrocarbon Radicals.

Using a combination of resonant two-photon two-color ionization (R2C2PI) and laser-induced fluorescence/dispersed fluorescence spectroscopy, we have examined the 2A″ ← 2A″ transition of the resonance-stabilized α-hydrofulvenyl radical, produced from methylcyclopentadiene dimer in a jet-cooled discharge. Like the related 1,4-pentadienyl and cyclohexadienyl radicals, the α-hydrofulvenyl Ã-state lifetime is orders of magnitude shorter than the predicted f-value implies, indicative of rapid nonradiative decay. The transition is fully allowed by symmetry but considerably weakened by transition moment interference. Intensity borrowing among a' modes brings about static (i.e., Condon) and vibronic (i.e., Herzberg-Teller) moments of similar size, the result being a spectrum substantially less origin-dominated than is usually observed for extensively delocalized radicals. Twenty -state modes and twelve -state modes are identified with high confidence and assignments for several others are suggested. In addition, from a series of two-color appearance potential scans with the -state zero-point level serving as an intermediate, we obtain a field-free adiabatic ionization energy (AIE) of 7.012(1) eV. For a set of 21 resonance-stabilized radicals bearing 5 to 11 carbon atoms, it emerges that the field-free AIE obtained by R2C2PI methods under jet-cooled conditions lies very close to the average of B3LYP/6-311G++(d,p) (with harmonic zero-point energy) and CBS-QB3 0 K calculations, with a mean absolute deviation of only 0.010(7) eV (approximately 1 kJ/mol). On average, this represents a nearly 10-fold improvement in accuracy over CBS-QB3 predictions for the same set of radicals.

Symmetry-Broken Electronic State of CsPbBr3 Cubic Perovskite Nanocrystals.

The development of densely packed, self-assembled perovskite nanocrystals (PeNCs) with a favorable transition dipole moment (TDM) orientation is crucial for their application in solution-processable electronic devices. In this study, we fabricated anisotropic CsPbBr3 PeNCs with a symmetry-broken electronic state on quartz substrates modified by 3-aminopropyltrimethoxysilane (APS). Densely packed and self-assembled monolayers of cubic PeNCs were formed on the substrates by using a dip coating technique. The angle-dependent absorption and photoluminescence (PL) spectra confirmed that the PeNC monolayer on the APS-treated substrate exhibited anisotropic electronic states in the in-plane and out-of-plane directions of the substrate. In contrast, when the quartz substrate was modified with the long alkyl silane coupling agent, octadecyltrimethoxysilane, the absorption and PL spectra exhibited no angular dependence, indicating the absence of anisotropy. Experimental and simulated results confirmed the presence of vertical TDMs in the densely packed PeNCs on the APS-treated substrate, which could be attributed to the effect of the amino groups of the APS on the facet of the cubic PeNCs facing the quartz substrate. Hence, surface chemical modifications of the substrate can aid in the precise control of the symmetry of the electronic states and TDM orientation in cubic PeNCs. These findings can promote the development of densely packed, high-coverage PeNC films with a controllable TDM orientation for applications in electronic devices such as solar cells, sensors, and light-emitting diodes.

Enhancing Circularly Polarized Luminescence Dissymmetry Factor of Chiral Cylindrical Molecules to -0.56 through Intramolecular Short-Range Charge Transfer.

High-performance circularly polarized luminescent (CPL) materials have received wide attention recently by virtue of broad application in circularly polarized light-emitting diodes, 3D display, and encryption. Reaching both high luminescence efficiency and strong luminescence dissymmetry factor (glum) is still a challenging goal that requires continuous efforts. Herein, we performed a systematic theoretical investigation on the chiroptical properties of helical cylindrical molecules (-)-[4]cyclo-2,6-anthracene [(-)-[4]CA2,6] and (P)-[4]cyclo-2,8-chrysenylene [(P)-[4]CC2,8], and found that the unique and symmetric cylindrical structure could make the transition dipole moment components offset along the cylindrical surface but concentrated along the vertical central axis. This structural superiority contributes the collinear electric and magnetic transition dipole moment vectors and thus the large glum. Based on the results of decomposed transition dipole moment vectors to individual atoms, an effective strategy to enhance the glum through introducing intramolecular short-range charge transfer by embedding B,N atoms is proposed. The decreased electric transition dipole moment and well-kept magnetic transition dipole moment enable the glum of B,N-embedded designed molecules (-)-[4]CA2,6-4BN and (P)-[4]CC2,8-4BN up to -0.31 and -0.56, respectively. This molecular-insight investigation deepens the understanding of the structure-property relationship and provides efficient guidance for improving glum of CPL materials.

Increasing the Magnetic Transition Dipole Moment of Chiral Perovskite Through Eu3+ Doping

AbstractChiral hybrid organic‐inorganic perovskites (HOIPs) are widely investigated due to their superior chiroptical and chiral spintronic properties. Research on the enhancement of chiroptical performance is highly important for the real application of chiral HOIPs. This work employed a rare earth doping strategy to increase the magnetic transition dipole moment of chiral 2D HOIPs R‐/S‐NPB (NPB = 1‐(1‐naphthyl) ethylammonium lead bromide). Doping with Eu3+ does not change the original layered NPB microstructure, and R‐/S‐NPB‐Eu exhibited the magnetic dipole‐allowed transition luminescence of Eu3+ at 594 nm (5D0→7F1). Circular polarized luminescence (CPL) spectra combined with theoretical calculations and transient photoluminescence measurements indicated that the introduction of Eu3+ can enhance the magnetic transition dipole moment of R‐/S‐NPB, thus resulting in an unprecedented glum of 0.05. To the best of our knowledge, this is the highest value for chiral perovskite films. This work combines the unique and superior optoelectronic properties of rare‐earth ions with chiral perovskite and develops an efficient strategy to increase its anisotropy factor, which can accelerate the development of chiral optoelectronics and spintronics towards real application.

Predicting offensive sector entry during transition moments in soccer

Transitions, rapid attacks after regaining possession, are a potent weapon, yet their lower frequency compared to organized attacks highlights a need for understanding factors that influence their success, particularly regarding offensive sector entry. This study investigates factors influencing the success of transitions, with a specific focus on predicting their ability to penetrate the opponent’s offensive sector. We analyzed 1911 ball recoveries from the 2018 to 2019 Greek SuperLeague. Chi-squared tests and binary logistic regression were employed to examine the influence of recovery type, number of defenders, passing patterns (including penetrative passes), and other variables on successful transitions. Our findings reveal that the likelihood of entering the offensive sector significantly increased when the ball was recovered in advanced areas, against fewer defenders, involved a high proportion of penetrative passes, and had a longer offensive sequence duration. This model provides a framework for predicting offensive sector entry during transitions, offering valuable insights for coaches seeking to optimize training drills and maximize transitional effectiveness.