Higher Excited States Research Articles

Interpretation of recently discovered single bottom baryons in the relativistic flux tube model

Following recent experimental progress in the study of bottom baryons, we systematically calculate the mass spectra of Λb, Ξb, Σb, Ξb′, and Ωb baryons with a quark-diquark picture in the framework of a relativistic flux tube model with spin-dependent interactions in the j-j coupling scheme. Furthermore, we calculate the strong decay width of bottom baryons decaying into a bottom baryon and a light pseudoscalar meson. Good agreement is found between the calculated masses and the experimentally available masses of singly bottom baryons. By analyzing both mass spectra and strong decay widths, we interpret Σb(6097) as a 1P(3/2−) state and Ξb(6100) as a 1P(1/2−) state of the Ξb baryon. The Ξb(6227) is identified to be an orbital excitation 1P of the Ξb′ baryon with JP=3/2−. Further, we determine Ξb(6327) and Ξb(6333) as a 1P(3/2−) state and 1P(5/2−) state, respectively, of Ξb′ baryon. From the obtained mass spectra, we construct the Regge trajectories in the (J,M2) plane, which are found to be essentially linear, parallel, and equidistant. Our predictions for higher orbital and radial excited states can help experimentalists identify missing excited states of singly bottom baryons. Published by the American Physical Society 2024

Masses of higher excited states of Ξc′ and Ωc baryons

Masses of higher excited states of Ξc′ and Ωc baryons

Studies of Z boson decay into double ϒ mesons at the NLO QCD accuracy

In this paper, we employ the nonrelativistic quantum chromodynamics (QCD) factorization to conduct a comprehensive examination of the Z boson decay into a pair of ϒ mesons, achieving accuracy at the next-to-leading-order (NLO) in αs. Our calculations demonstrate that the quantum electrodynamics (QED) diagrams are indispensable in comparison to the pure QCD diagrams, and the implementation of QCD corrections markedly enhances the QCD results, whereas it substantially diminishes the QED results. To ensure consistency with the experimental methodology, we have taken into account the feed-down transitions originating from higher excited states, which exhibit significant relevance. Combining all the contributions, we arrive at the NLO prediction of BZ→ϒ(nS)+ϒ(mS)∼10−11, which is notably lower than the upper limits set by CMS. Published by the American Physical Society 2024

Effect of multi-donor and extended π-conjugation in ferrocene appended indanedione chromophores for aggregation induced emission enhancement (AIEE) and nonlinear optics†

A new (D-D’π-A) type ferrocene and methoxyphenyl (D-D′) conjugated indanedione (A) based linear and π-extended multi-donor-π-acceptor chromophores 1–4 were synthesized and characterized. The chromophores 2–4 were further investigated by single-crystal analysis through X-ray diffraction, revealing centrosymmetric space groups with non-covalent interactions (inter, intramolecular hydrogen bonding, and C–H…π interactions) and these molecular packing interactions favor SHG efficiencies. Electrochemical studies show the one-electron charge transfer (Fe2+⇌Fe3+) and observed greater redox potential of chromophore 4 than the parent ferrocene due to the substitution effect. The solvatochromic studies in emission spectra resulted in redshift (56–109 nm) for the chromophores 1–4 by increasing the solvent polarities, which indicates higher excited state stabilization relative to the ground state, results effective intramolecular charge transfer process within the chromophores. The occurrence of ferrocene moieties lowers the fluorescence intensities of the chromophores 1–4, which was overcome through aggregation induced emission enhancement (AIEE) studies at 60 % (THF/H2O). The AIEE state also shows 23 times higher quantum yield than the THF solution for chromophore 4. In addition, a thin film using polymethyl methacrylate as a binder shows a significant blue shift with higher emission intensity than those obtained in the solution due to the intermolecular interactions and enhancement of viscosity. The SHG efficiency studied using the Kurtz and Perry powder technique results in a higher value for chromophore 4 (2 times higher than the reference KDP) attribute to the multi donors, acceptor, and extended π conjugation reducing the anti-parallel alignment in the solid state. The computational calculations were done to validate the experimental results using B3LYP/6-31+G** level of theory.

Bound-state evolution of Dirichlet waveguide with Neumann window(s) in transverse electric fields

The influence of electric field E on a straight Dirichlet waveguide with Neumann window(s) of arbitrary length L is studied theoretically for 2D and 3D geometries. The energy spectrum for the corresponding bound states was obtained and their dependence on E was analysed. At low E , the boundary of the window(s) influenced the properties of the particle contrary to the high E case, where the energies and localization of particle were seen similar in all the geometries. The critical lengths L cr , at which higher excited state emerges into the continuum, at different E were found and their behavior was explained qualitatively. It was found that at high E , the critical lengths of Dirichlet-Neumann boundary window approach the Neumann-Neumann boundary window. This is due to the increase in the fundamental propagation threshold of transverse modes in the wall and window region. On the other hand, the Neumann-Dirichlet boundary window showed an opposite behavior. Furthermore, the polarization of ground state was obtained for different geometries. It was proved that at small L, the polarization reduces to its 1D case. A mathematical treatment and semi classical explanation was provided. Comparative analysis of the 2D and 3D geometries reveals their qualitative similarity and quantitative differences.

Multiphoton-Driven Photocatalytic Defluorination of Persistent Perfluoroalkyl Substances and Polymers by Visible Light.

Perfluoroalkyl substances (PFASs) and fluorinated polymers (FPs) have been extensively utilized in various industries, whereas their extremely high stability poses environmental persistence and difficulty in waste treatment. Current decomposition approaches of PFASs and FPs typically require harsh conditions such as heating over 400 °C. Thus, there is a pressing need to develop a new technique capable of decomposing them under mild conditions. Here, we demonstrated that perfluorooctanesulfonate (PFOS), known as a "persistent chemical," and Nafion, a widely utilized sulfonated FP for ion-exchange membranes, can be efficiently decomposed into fluorine ions under ambient conditions via the irradiation of visible LED light onto semiconductor nanocrystals (NCs). PFOS was completely defluorinated within 8-h irradiation of 405-nm LED light, and the turnover number of the C-F bond dissociation per NC was 17200. Furthermore, 81 % defluorination of Nafion was achieved for 24-h light irradiation, demonstrating the efficient photocatalytic properties under visible light. We revealed that this decomposition is driven by cooperative mechanisms involving light-induced ligand displacements and Auger-induced electron injections via hydrated electrons and higher excited states. This study not only demonstrates the feasibility of efficiently breaking down various PFASs and FPs under mild conditions but also paves the way for advancing toward a sustainable fluorine-recycling society.

Multiphoton‐Driven Photocatalytic Defluorination of Persistent Perfluoroalkyl Substances and Polymers by Visible Light

AbstractPerfluoroalkyl substances (PFASs) and fluorinated polymers (FPs) have been extensively utilized in various industries, whereas their extremely high stability poses environmental persistence and difficulty in waste treatment. Current decomposition approaches of PFASs and FPs typically require harsh conditions such as heating over 400 °C. Thus, there is a pressing need to develop a new technique capable of decomposing them under mild conditions. Here, we demonstrated that perfluorooctanesulfonate (PFOS), known as a “persistent chemical,” and Nafion, a widely utilized sulfonated FP for ion‐exchange membranes, can be efficiently decomposed into fluorine ions under ambient conditions via the irradiation of visible LED light onto semiconductor nanocrystals (NCs). PFOS was completely defluorinated within 8‐h irradiation of 405‐nm LED light, and the turnover number of the C−F bond dissociation per NC was 17200. Furthermore, 81 % defluorination of Nafion was achieved for 24‐h light irradiation, demonstrating the efficient photocatalytic properties under visible light. We revealed that this decomposition is driven by cooperative mechanisms involving light‐induced ligand displacements and Auger‐induced electron injections via hydrated electrons and higher excited states. This study not only demonstrates the feasibility of efficiently breaking down various PFASs and FPs under mild conditions but also paves the way for advancing toward a sustainable fluorine‐recycling society.

Dual Fluorescence and Phosphorescence Emissions from Dye-Modified (NCN)-Bismuth Pincer Thiolate Complexes.

We report the synthesis, characterization, and photophysical properties of four new dye-modified (NCN)Bi pincer complexes with two mercaptocoumarin or mercaptopyrene ligands. Their photophysical properties were probed by UV/vis spectroscopy, photoluminescence (PL) studies, and time-dependent density functional theory (TD-DFT) calculations. Absorption spectra of the complexes are dominated by mixed pyrene or coumarin π → π*/n(pS) → pyrene or coumarin π* transitions. While unstable toward reductive elimination of the corresponding disulfide under irradiation at room temperature, the complexes provide stable emissions at 77 K. Under these conditions, coumarin complexes 2 and 4 exhibit exclusively green phosphorescence at 508 nm. In contrast, the emissive properties of pyrene complexes 1 and 3 depend on the excitation wavelength and on sample concentration. Irradiation into the lowest-energy absorption band exclusively triggers red phosphorescence from the pyrenyl residues at 640 nm. At concentrations c < 1 μM, excitation into higher excited electronic states results in blue pyrene fluorescence. With increasing c (1-100 μM), the emission profile changes to dual fluorescence and phosphorescence emission, with a steady increase of the phosphorescence intensity, until at c ≥ 1 mM only red phosphorescence ensues. Progressive red-shifts and broadening of steady-state excitation spectra with increasing sample concentration suggest the presence of static excimers, as we observe it for concentrated solutions of pyrene. Crystalline and powdered samples of 1 indeed show intermolecular association through π-stacking. TD-DFT calculations on model dimers and a tetramer of 1 support the idea of aggregation-induced intersystem crossing (AI-ISC) as the underlying reason for this behavior.

Thermally activated delayed fluorescence hosts based on carbazole and quinazoline derivatives for red organic LEDs

Thermally activated delayed fluorescence (TADF) materials have been regarded as promising host materials for fluorescent and phosphorescent guest materials to achieve high performance organic light-emitting diodes (OLEDs). In this work, three molecules, PhCQ, m-PyCQ and p-PyCQ, using carbazole derivatives as donor and quinazoline units as acceptor were designed and synthesized. Both theoretical and experimental results showed that PhCQ, m-PyCQ and p-PyCQ possess TADF properties with higher triplet excited states than red phosphorescent guest, RD-1. When used as host materials for RD-1, it was found that the emission spectrum of PhCQ has the largest overlap with the absorption spectrum of RD-1, which is conducive to Förster resonance energy transfer (FRET) between the host to the guest. As a result, red phosphorescent OLED device based on PhCQ host exhibited the best performances with the maximum external quantum efficiency (EQE) of 37.2 %. When the brightness is 1000 cd/m2, the EQE is still as high as 33.0 %.

Exploring the Charge-Transport and Optical Characteristics of Organic Doublet Radicals: A Theoretical and Experimental Study with Photovoltaic Applications.

Herein, we present a series of stable radicals containing a trityl carbon-centered radical moiety exhibiting interesting properties. The radicals demonstrate the most blue-shifted anti-Kasha doublet emission reported so far with high color purity (full width at half-maximum of 46 nm) and relatively high photoluminescence quantum yields of deoxygenated toluene solutions reaching 31%. The stable radicals demonstrate equilibrated bipolar charge transport with charge mobility values reaching 10-4 cm2/V·s at high electric fields. The experimental results in combination with the results of TD-DFT calculations confirm that the blue emission of radicals violates the Kasha rule and originates from higher excited states, whereas the bipolar charge transport properties are found to stem from the particularity of radicals to involve the same molecular orbital(s) in electron and hole transport. The radicals act as the efficient materials for interlayers, passivating interfacial defects and enhancing charge extraction in PSCs. Consequently, this leads to outstanding performance of PSC, with power conversion efficiency surpassing 21%, accompanied by a remarkable increase in open-circuit voltage and exceptional stability.

Modular Assembly of Acridines by Integrating Photo-Excitation of o-Alkyl Nitroarenes with Copper-Promoted Cascade Annulation.

Acridine frameworks stand as pivotal architectural elements in pharmaceuticals and photocatalytic applications, owing to their chemical adaptability, biological activity, and unique excited-state dynamics. Conventional synthetic routes often entail specialized starting materials, anaerobic or moisture-free conditions, and elaborate multi-stage manipulations for incorporating diverse functionalities. Herein, we present a convergent approach integrating photo-excitation of readily available ortho-alkyl nitroarenes with copper-promoted cascade annulation. This innovative system enables an aerobic, one-pot reaction of o-alkyl nitroarenes with arylboronic acids, thereby streamlining the modular construction of a wide array of acridine derivatives with various functional groups. This encompasses symmetrical, unsymmetrical and polysubstituted varieties, some of which are otherwise exceptionally difficult to synthesize. Furthermore, it significantly improves the production of structurally varied acridinium salts, featuring enhanced photophysical properties, high excited state potentials (E*red=2.08-3.15 V), and exhibiting superior performance in intricate photoredox transformations.

Modular Assembly of Acridines by Integrating Photo‐Excitation of o‐Alkyl Nitroarenes with Copper‐Promoted Cascade Annulation

Acridine frameworks stand as pivotal architectural elements in pharmaceuticals and photocatalytic applications, owing to their chemical adaptability, biological activity, and unique excited‐state dynamics. Conventional synthetic routes often entail specialized starting materials, anaerobic or moisture‐free conditions, and elaborate multi‐stage manipulations for incorporating diverse functionalities. Herein, we present a convergent approach integrating photo‐excitation of readily available ortho‐alkyl nitroarenes with copper‐promoted cascade annulation. This innovative system enables an aerobic, one‐pot reaction of o‐alkyl nitroarenes with arylboronic acids, thereby streamlining the modular construction of a wide array of acridine dervatives with various functional groups. This encompasses symmetrical, unsymmetrical and polysubstituted varieties, some of which are otherwise exceptionally difficult to synthesize. Furthermore, it significantly improves the production of structurally varied acridinium salts, featuring enhanced photophysical properties, high excited state potentials (E*red = 2.08−3.15 V), and exhibiting superior performance in intricate photoredox transformations.

In situ fabrication of oxygen deficient Bi2MoO6/InVO4/CeVO4 dual S-scheme ternary heterostructure for robust photocatalytic H2 and H2O2 production

Mild in situ synthesis of ternary dual S-scheme heterostructure photocatalyst with high redox ability of photo-excitons is a pragmatic approach for achieving rapid activation of tenacious atmospheric molecules. In the present study, a series of Bi2MoO6/InVO4/CeVO4 ternary heterostructures were constructed by in situ deposition of Bi2MoO6 nanoplates over one pot synthesised InVO4/CeVO4 using a facile oil bath heating method. The as-synthesised heterostructure materials were comprehensively characterised to understand their structural, optical, electrochemical and morphological properties. The ternary heterostructure displayed a distinct morphology consisting of Bi2MoO6 nanoplates, CeVO4 nanosheets and InVO4 nanorods. The significant intergrowth among the constituent phases through the in situ coupling strategy also led to the construction of tight interfacial microscopic junctions. The important attributes of the ternary heterostructures included intense photon absorption in whole UV–visible region, drastic decrease in photogenerated charge recombination and higher excited state lifetime. Both InVO4 and CeVO4 individually as well as the ternary heterostructure contained surface oxygen vacancies that further promoted efficient charge separation and activation of atmospheric molecules. The optimised ternary photocatalyst displayed 2314 μmol/g/h H2 generation and 1700 μM/g/h H2O2 production which are 12–86 and 11–27 times higher than the pristine semiconductors, respectively. Detailed band position assessment and radical entrapment analysis suggested the occurrence of a dual S-scheme charge transfer mechanism that rationally accounted for the remarkable enhancement in the photocatalytic performance.

Relaxation dynamics of higher excited states of perylene-substituted perylene bisimide derivatives.

Stepwise two-photon absorption processes have received considerable attention, especially in photocatalysis, due to their relatively lower power threshold, characteristic spatial selectivity, amplification of chemical reactions, and so on. Meanwhile, studies on the relaxation dynamics of higher excited states in condensed systems have been limited for several molecular systems due to the short-lived nature of these states. In this study, we synthesized perylene-substituted perylene bisimide (PBI) and its derivate as model compounds and investigated their excited-state dynamics, including higher excited states, using pump-repump-probe spectroscopy. We revealed that these molecules form charge-transfer (CT) states instantaneously after the excitation, regardless of whether it is the perylene moiety or the PBI moiety that is excited. The lifetime of the CT state was shorter when the distance between the donor (perylene) and the acceptor (PBI) was shorter. Moreover, we also revealed that a higher-lying CT state generated by the stepwise excitation of the CT state using a 740-nm pulse induced Stark effect to the neighboring perylene moiety. The Stark effect not only gives more detailed information about the CT state, but also presents the possibility of new photofunctions, such as instantaneous modulation of the electronic state to achieve optimal electronic properties. These insights contribute to understanding advanced photochemical reactions and would be important for exploring photocatalytic reactions involving higher excited states.

Ratiometric Chemosensors That Are Capable of Quantifying Hydrostatic Pressure Stimulus: A Case of Porphyrin Tweezers.

Investigating chemosensors that are capable of quantifying pressure in solution, particularly hydrostatic pressure, which is one of the mechanical forces, is an attractive challenge in chemistry from the viewpoint of "mechano"-science. Herein, we report the investigation of chiral porphyrin tweezers, Por-Cy and Por-DPhEt, comprising different flexible linkers; Por-Cy and Por-DPhEt displayed distinct ratiometric signaling by using the higher excited S2 state with a standard excited S1 level. A novel operative mechanism using the S1/S2 fluorescence ratio was revealed using hydrostatic pressure-ultraviolet/visible (UV/vis), fluorescence/excitation, circular dichroism spectroscopy, and lifetime measurements, which can be further controlled by the open-closed conformational change inherent in the tweezer skeleton. Furthermore, the fluorescent chiral tweezers exhibited a promising |g lum| of 2.9 × 10-3, indicating that they are potential candidates for sensory applications in chiral environments. This study provides opportunities for the development of smart pressure-responsive chemosensors.

New features in Franck–Hertz experiment with argon: experiment and Monte Carlo simulation

In this work, a homemade apparatus was built to perform the Franck–Hertz experiment with argon. The lowest energy state and the higher energy state of argon can be excited by the Franck–Hertz experiment. The excitation energies of the argon atom are measured by using the setup. The obtained higher excitation energy of argon atoms is 13.73 ± 0.28 eV, for the mixture of higher energy states 3s 23p 53d and 3s 23p 54p. A plate capacitor model was constructed to simulate the inelastic collisions between electrons and argon atoms using the Monte Carlo method. The simulated current curve and electron energy distribution agrees with that of Franck–Hertz experiments, especially the features of higher excited state. The Monte Carlo simulation indicates the deformed electron energy distribution results from the change in excitation proportion of energy levels during the collisions of electrons and argon atoms. Moreover, the new features in Franck–Hertz curve are ascribed to the higher excitation states of argon atoms. The experimental setup has been applied to undergraduate physics experiment teaching in college. Students can perform the Franck–Hertz curve measurement of not only the lowest excited state, but also the higher excited states of argon. In addition, students can do the Monte Carlo simulations for the experimental Franck–Hertz curves and gain a better understanding of electron-argon atom collisions in the experiment. The new designed experiment will make students more familiar with the quantum behavior in atomic physics and quantum mechanics course.

Electron capture and excitation in intermediate-energy He2+–H(1s,2s) collisions

Abstract The semiclassical non-perturbative atomic orbital close-coupling approach has been employed to study the electron capture and excitation processes in He2+-H(1s) and He2+-H(2s) collision systems. In order to ensure the accuracy of our calculated cross sections, a large number of high excited states and pseudostates are included in the expansion basis sets which centered on target and projectile, respectively. The total and partial charge transfer and excitation cross sections are obtained for a wide-energy domain ranging from 1 to 200 keV/amu. The present calculations are also compared with the results from other theoretical methods. These cross section data is useful for the investigation of astrophysics and laboratory plasma.

Varying primordial state fractions in exo- and endothermic SIDM simulations of Milky Way-mass haloes

Abstract Self-interacting dark matter (SIDM) is increasingly studied as a potential solution to small-scale discrepancies between simulations of cold dark matter (CDM) and observations. We examine a physically motivated two-state SIDM model with both elastic and inelastic scatterings. In particular, endothermic, exothermic, and elastic scattering have equal transfer cross sections at high relative velocities (vrel ≳ 400 km s−1). In a suite of cosmological zoom-in simulation of Milky Way-size haloes, we vary the primordial state fractions to understand the impact of inelastic dark matter self-interactions on halo structure and evolution. In particular, we test how the initial conditions impact the present-day properties of dark matter haloes. Depending on the primordial state fraction, scattering reactions will be dominated by either exothermic or endothermic effects for high and low initial excited state fractions respectively. We find that increasing the initial excited fraction reduces the mass of the main halo, as well as the number of subhaloes on all mass scales. The main haloes are cored, with lower inner densities and higher outer densities compared with CDM. Additionally, we find that the shape of the main halo becomes more spherical the higher the initial excited state fraction is. Finally, we show that the number of satellites steadily decreases with initial excited state fraction across all satellite masses.

Hückel molecular orbital theory on a quantum computer: A scalable system-agnostic variational implementation with compact encoding.

Hückel molecular orbital (HMO) theory provides a semi-empirical treatment of the electronic structure in conjugated π-electronic systems. A scalable system-agnostic execution of HMO theory on a quantum computer is reported here based on a variational quantum deflation (VQD) algorithm for excited state quantum simulation. A compact encoding scheme is proposed here that provides an exponential advantage over the direct mapping and allows for quantum simulation of the HMO model for systems with up to 2n conjugated centers with n qubits. The transformation of the Hückel Hamiltonian to qubit space is achieved by two different strategies: an iterative refinement transformation and the Frobenius-inner-product-based transformation. These methods are tested on a series of linear, cyclic, and hetero-nuclear conjugated π-electronic systems. The molecular orbital energy levels and wavefunctions from the quantum simulation are in excellent agreement with the exact classical results. However, the higher excited states of large systems are found to suffer from error accumulation in the VQD simulation. This is mitigated by formulating a variant of VQD that exploits the symmetry of the Hamiltonian. This strategy has been successfully demonstrated for the quantum simulation of C60 fullerene containing 680 Pauli strings encoded on six qubits. The methods developed in this work are easily adaptable to similar problems of different complexity in other fields of research.

Resonant Tip-Enhanced Raman Spectroscopy of a Single-Molecule Kondo System.

Tip-enhanced Raman spectroscopy (TERS) under ultrahigh vacuum and cryogenic conditions enables exploration of the relations between the adsorption geometry, electronic state, and vibrational fingerprints of individual molecules. TERS capability of reflecting spin states in open-shell molecular configurations is yet unexplored. Here, we use the tip of a scanning probe microscope to lift a perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecule from a metal surface to bring it into an open-shell spin one-half anionic state. We reveal a correlation between the appearance of a Kondo resonance in differential conductance spectroscopy and concurrent characteristic changes captured by the TERS measurements. Through a detailed investigation of various adsorbed and tip-contacted PTCDA scenarios, we infer that the Raman scattering on suspended PTCDA is resonant with a higher excited state. Theoretical simulation of the vibrational spectra enables a precise assignment of the individual TERS peaks to high-symmetry Ag modes, including the fingerprints of the observed spin state. These findings highlight the potential of TERS in capturing complex interactions between charge, spin, and photophysical properties in nanoscale molecular systems and suggest a pathway for designing single-molecule spin-optical devices.