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Metamaterials and chiral sensing: a review of fundamentals and applications
摘要： Chirality, a property of broken mirror symmetry, prevails in nature. Chiral molecules show different biochemical behaviors to their mirror molecules. For left or right circularly polarized lights, the fundamental chiral states of electromagnetic fields interact differently with chiral matter, and this effect has been used as a powerful tool for the detection of chiral molecules. This optical sensing, also termed chiral sensing, is not only easy to implement but also non-invasive to the analytes. However, the measurements made by the optical sensing of chiral molecules are challenging, as chiroptical signals are extremely weak. Recent years have seen active research efforts into metamaterial and plasmonic platforms for manipulating local fields to enhance chiroptical signals. This metamaterial approach offers new possibilities of chiral sensing with high sensitivity. Here, we review the recent advances in chiral sensing using metamaterial and plasmonic platforms. In addition, we explain the underlying principles behind the enhancement of chiroptical signals and highlight practically efficient chiral sensing platforms. We also provide perspectives that shed light on design considerations for chiral sensing metamaterials and discuss the possibility of other types of chiral sensing based on resonant metamaterials.
关键词： chiral sensing,chiral molecules,optical rotatory dispersion (ORD),chiroptical spectroscopy,circular dichroism (CD),enantiomers,plasmonics,metamaterials,optical spectroscopy
更新于2025-09-19 17:15:36
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Deep Learning Spectroscopy: Neural Networks for Molecular Excitation Spectra
摘要： Deep learning methods for the prediction of molecular excitation spectra are presented. For the example of the electronic density of states of 132k organic molecules, three different neural network architectures: multilayer perceptron (MLP), convolutional neural network (CNN), and deep tensor neural network (DTNN) are trained and assessed. The inputs for the neural networks are the coordinates and charges of the constituent atoms of each molecule. Already, the MLP is able to learn spectra, but the root mean square error (RMSE) is still as high as 0.3 eV. The learning quality improves significantly for the CNN (RMSE = 0.23 eV) and reaches its best performance for the DTNN (RMSE = 0.19 eV). Both CNN and DTNN capture even small nuances in the spectral shape. In a showcase application of this method, the structures of 10k previously unseen organic molecules are scanned and instant spectra predictions are obtained to identify molecules for potential applications.
关键词： artificial intelligence,excitation spectra,organic molecules,DFT calculations,neural networks
更新于2025-09-19 17:15:36
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Simultaneous UV- and ion processing of astrophysically relevant ices
摘要： Context. Interstellar ices are known to be simultaneously processed by both cosmic-ray bombardment and UV photolysis. Our knowledge of the effects of energetic processing on relevant icy samples is mainly based on laboratory investigations. In the past 35 years many experiments have been performed to study these effects separately but, to the best of our knowledge, never simultaneously. Aims. The aim of this work is to study the effects of simultaneous processing of ices by both cosmic rays and UV photons to investigate to what extent the combined effect of ion bombardment and UV photolysis influences the chemical pathways. Methods. We carried out the simultaneous processing of CH3OH:N2 ice held at 16 K by 200 keV H+ ions and Lyman-alpha 10.2 eV UV photons. The samples were analyzed by in situ transmission infrared spectroscopy. The un-combined processes of UV irradiation and bombardment by H+ ions of CH3OH:N2 ice were also studied. This mixture was chosen because the effects of ion bombardment and UV photolysis on methanol and nitrogen have been extensively studied in previous investigations. This mixture enables one to investigate whether simultaneous processing (a) influences the destruction of original species; (b) influences the formation of new species; or (c) causes synergistic effects since Lyman-alpha photons have a very low efficiency in breaking the dinitrogen bond because N2 is almost transparent at Lyman-alpha wavelengths. Results. After processing a CH3OH:N2 sample, the intensity of the methanol bands was observed to decrease at the same rate in all cases. After ion bombardment, species such as CO2, CO, H2CO, CH4, N2O, HNCO, and OCN? are formed in the ice mixture. After UV photolysis, species such as CO2, CO, H2CO, and CH4 are formed, but no N-bearing species are detected. Spectra of ices processed by both UV photons and ions were compared with spectra of ices bombarded only by ions. We find that there are no differences in the band area and profile of N-bearing species for the two types of experiment at the same ion fluence; therefore, the addition of UV irradiation to ion bombardment does not affect the abundance of N-bearing species. The initial formation rate of CH4, within the experimental uncertainties, is the same in all cases studied, while the saturation value of CH4 is higher for UV photolysis than for ion bombardment when they act separately. In the case of simultaneous processing, when the dose (eV/16u) given by UV photons is similar to the dose given during ion bombardment, the saturation value of CH4 reaches a value intermediate between the value obtained after UV photolysis and ion bombardment separately. Conclusions. Our results confirm that when UV photolysis and ion bombardment act separately, their effects are very similar from a qualitative point of view, while significant quantitative difference may exist. In the case of simultaneous processing we did not detect any synergistic effect, but in some instances the behavior of newly formed species (such as CH4) can significantly depend on the UV/ions dose ratio.
关键词： astrochemistry,ISM: molecules,techniques: spectroscopic,molecular processes,methods: laboratory
更新于2025-09-19 17:15:36
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Far-infrared CO and H <sub/>2</sub> O emission in intermediate-mass protostars
摘要： Context. Intermediate-mass young stellar objects (YSOs) provide a link to understanding how feedback from shocks and UV radiation scales from low- to high-mass star forming regions. Aims. Our aim is to analyze excitation of CO and H2O in deeply embedded intermediate-mass YSOs and compare it with similar studies on low-mass and high-mass YSOs. Methods. Herschel/PACS spectral maps are analyzed for six YSOs with bolometric luminosities of Lbol ～ 102?103 L☉. The maps cover spatial scales of ～104 AU in several CO and H2O lines located in the ～55–210 μm range. Results. Rotational diagrams of CO show two temperature components at Trot ～ 320 K and Trot ～ 700–800 K, comparable to low- and high-mass protostars probed at similar spatial scales. The diagrams for H2O show a single component at Trot ～ 130 K, as seen in low-mass protostars, and about 100 K lower than in high-mass protostars. Since the uncertainties in Trot are on the same order as the difference between the intermediate and high-mass protostars, we cannot conclude whether the change in rotational temperature occurs at a specific luminosity or whether the change is more gradual from low- to high-mass YSOs. Conclusions. Molecular excitation in intermediate-mass protostars is comparable to the central 103 AU of low-mass protostars and consistent within the uncertainties with the high-mass protostars probed at 3 × 103 AU scales, suggesting similar shock conditions in all those sources.
关键词： stars: protostars,ISM: jets and outflows,ISM: molecules
更新于2025-09-19 17:15:36
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Electron correlation effects in the photoionization of CO and isoelectronic diatomic molecules
摘要： This paper investigates the first sigma satellite band, which is by far the most prominent, in the valence photoelectron spectra for a set of isoelectronic diatomic molecules: carbon monoxide, carbon monosulfide, carbon monoselenide, silicon monoxide and boron monofluoride. In particular, we analyze the effect of the electronic structure, with the change of the atomic pair along the row and column of the periodic table on the position of the satellite peak as well as on the related dynamical observables profiles. For this investigation, highly correlated calculations have been performed on the primary ionic states and the satellite band for all the molecules considered. Cross sections for the primary ionic states, calculated using Dyson orbitals, have been compared with those obtained with Hartree–Fock and Density Functional Theory to probe the impact of the correlation in the bound states on the photoionization observables. Limitations of a simple intensity borrowing mechanism clearly result from the analysis of the satellite state, characterized by different features with respect to the relevant primary states.
关键词： isoelectronic molecules,photoelectron spectra,photoionization,electron correlation,Dyson orbitals
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Theoretical and Experimental Studies of Breather Wave Molecules
摘要： The formation of localized wave structures has attracted a significant research interest in a variety of conservative and dissipative systems, including photonics, plasma physics, Bose-Einstein condensates, fluid mechanics, biology and chemistry. Besides their formation, their mutual interactions such as collisions and formation of stable bound states have been particularly investigated in laser physics [1-3]. Such dissipative multi-soliton complexes, also called photonic molecules, result from self-organization phenomena, showing dynamics similar to matter molecules, such as synthesis and vibration. The build-up and transient regimes of dissipative localized structures in mode-locked fiber lasers are currently the subject of intense studies by means of real-time ultrafast measurements [2-3]. By contrast to the soliton molecules in dissipative cavities, which are described by Ginzburg-Landau equation, here we study conservative fiber systems driven by the integrable NLS equation [4]. More specifically, we present the theoretical description of the breather molecule based on the NLS equation. We find that the breather molecule exhibits quasi-periodic or exact periodic oscillatory dynamics according to the characteristic frequencies of elementary breathers. Figures 1(a) and 1(b) show the evolution of the intensity profile of two (a) and three (b) breathers based on the N-breather solution of standard NLS equation, where each breather can be accurately described by four key parameters [5-7]. These co-propagative breathers can exhibit both dissociated state (a1-b1) and bound state (a2-b2) behaviours, depending on the temporal matching between them. Next, we present our experimental results based on the propagation of arbitrarily shaped light waves and using a single-mode optical fiber workbench (a similar setup can be found in ref. [7]). As a general case, when temporal matching is satisfied, two individual breathers will be tightly bounded as a chain during propagation, [see Fig. 1(c1), where the key parameters of the breathers are listed in the caption]. We select three nodes of this breather molecule and present the snapshot of the measured amplitude profile in Fig. 1(c3) – each node exhibits the typical X-shape signature in the plane (ξ, τ), which is predicted by the theory in Fig. 1(c2).
关键词： soliton molecules,localized wave structures,photonic molecules,breather wave molecules,NLS equation
更新于2025-09-19 17:13:59
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Delocalized molecule surface electronic modification for enhanced performance and high environmental stability of CsPbI2Br perovskite solar cells
摘要： All-inorganic perovskites have drawn tremendous attentions in view of their superb thermal stability. However, unavoidable defects near the perovskite surface seriously hampers carrier transport and easily results in ion accumulation at the interface of perovskite layer and charge transport layer. Herein, delocalized thiazole and imidazole derivatives iodide salts functionalized on perovskite surface have been investigated comprehensively. These two salts post-treatment on perovskite could efficiently passivate traps arising from Cs+ or I- vacancies. Additionally, these highly п-conjugated delocalized molecules can contribute to the efficient charge transport and prevent ions accumulation at the interface. As a result, sulfur-contained aminothiazolium iodide (ATI) post-treated CsPbI2Br devices showed simultaneous enhanced current density and voltage due to its higher interaction with perovskite lattice, this led to a champion efficiency of 13.91% with superb fill factor of more than 80%, which exhibited dramatic enhancement compared with the control samples (10.12%). Furthermore, surface passivation with delocalized molecules could effectively stabilize CsPbI2Br phase at room temperature or 80 °C annealing in ambient condition (65% RH). Equally important, this surface passivation allowed competitive efficiency of 11.26% with a large-area device (1.00 cm2). This high kill tolerant approach provide a new route to fabricate inorganic perovskite devices with higher efficiency and stability.
关键词： rapid charge transfer,surface passivation,all-inorganic perovskite,delocalized molecules,higher performance
更新于2025-09-19 17:13:59
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Quantum collapse as reduction from a continuum of conditional amplitudes in an entangled state to a single actualized amplitude in the collapsed state
摘要： According to the Copenhagen interpretation of quantum mechanics a measurement leads to the collapse of a quantum system. A uni?ed description of a quantum system before and after measurement of the position ra1 and the spin sa1 of one of its electrons is proposed based on the conditional amplitude and its density. Quantum collapse is described as reduction from continuum of the conditional amplitudes {(cid:2)(x2, . . . , xN |rh1 )} in an initial quantum state to the single actualized amplitude (cid:2)(x2, . . . , xN |ra1 ) in a collapsed state. The latter state contains the information about quantum entanglement, the extraction of which with fragment entanglement measure is demonstrated for the realistic valence bond models of the dissociating dihydrogen and ethylene molecules.
关键词： ethylene molecules,quantum collapse,dihydrogen,conditional amplitude,quantum entanglement,valence bond models
更新于2025-09-19 17:13:59
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Enhanced photovoltaic performance of quinoxaline-based small molecules through incorporating trifluoromethyl substituents
摘要： Two D-A-D type quinoxaline-based small molecules have been synthesized by Suzuki coupling reaction for solution-processable organic photovoltaic cells (OPVs). The electron-donating triphenyl-amine was connected to both ends of an electron-withdrawing 2,3-diphenylquinoxaline core through thiophene bridge to produce QxTPA. In addition, QxCF3TPA was formed by introducing strong electron-withdrawing trifluoromethyl (CF3) groups into the para-position of the phenyl ring at the 2,3-position of quinoxaline core in QxTPA to explore their effect on the various properties of small molecules. The finding revealed the significant contributions of CF3 substituents in enhancing the photovoltaic performances of OPVs with QxCF3TPA compared to the reference case with QxTPA.
关键词： Small molecules,triphenylamine,trifluoromethyl,organic photovoltaic cell,2,3-diphenylquinoxaline
更新于2025-09-19 17:13:59
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Laser-Cooled Polyatomic Molecules for Improved Electron Electric Dipole Moment Searches
摘要： Doppler and Sisyphus cooling of 174YbOH are achieved and studied. This polyatomic molecule has high sensitivity to physics beyond the Standard Model and represents a new class of species for future high-precision probes of new T-violating physics. The transverse temperature of the YbOH beam is reduced by nearly two orders of magnitude to < 600 μK and the phase-space density is increased by a factor of > 6 via Sisyphus cooling. We develop a full numerical model of the laser cooling of YbOH and ?nd excellent agreement with the data. We project that laser cooling and magneto-optical trapping of long-lived samples of YbOH molecules are within reach and these will allow a high sensitivity probe of the electric dipole moment (EDM) of the electron. The approach demonstrated here is easily generalized to other isotopologues of YbOH that have enhanced sensitivity to other symmetry-violating electromagnetic moments.
关键词： polyatomic molecules,electron electric dipole moment,laser cooling,Sisyphus cooling,YbOH
更新于2025-09-19 17:13:59