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Spectroscopic and Theoretical Studies of Dual Fluorescence in 2-Hydroxy-N-(2-phenylethyl)benzamide Induced by ESIPT Process – Solvent Effects
摘要： This work discusses the theoretical ([TD]DFT) and spectroscopic investigation into 2-Hydroxy-N-(2-phenylethyl)benzamide (SAL3) and its physiochemical behaviour in the selected organic solvents. The compound demonstrated a dual fluorescence effect in alcoholic solutions (methanol, ethanol, isopropanol), while in acetonitrile (ACN), dimethylsulfoxide (DMSO) and non-polar solvents (n-Hexane, n-Heptane, chloroform) only a single emission maximum was observed. The noticeable shortening of average fluorescence lifetime, the employed detailed analysis of solvatochromic shifts of absorption spectra in the function of polarizability related to a change in the induction polarization of the environment and, above all, the performed quantum-mechanical calculations [TD] DFT with a detailed analysis of excited states, clearly indicate a connection between the observed fluorescence effects and processes related to changes in the system’s structure in the excited state. Based on these experimental and theoretical studies, it has been proposed that the environment (solvent) polarity-induced dual fluorescence effect in SAL3 is related to the Excited-State Intramolecular Proton Transfer (ESIPT) process. Also, the quantum-mechanic studies [TD] DFT point to the specific conformation of SAL3 molecule characteristic of dual fluorescence emission.
关键词： dual fluorescence effect,salicylic acid derivatives,[TD] DFT calculations,molecular spectroscopy,H-bonds
更新于2025-09-23 15:23:52
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Dynamical distortions of structural signatures in molecular high-order harmonic spectroscopy
摘要： We study the signature of two-center interferences in molecular high-order harmonic spectra, with an emphasis on the spectral phase. With the help of both ab initio computations based on the time-dependent Schr?dinger equation and the molecular strong-field approximation (SFA) as developed by Chiril? et al. [Phys. Rev. A 73, 023410 (2006)] and Faria [Phys. Rev. A 76, 043407 (2007)], we observe that the phase behavior is radically different for the short and the long trajectory contributions. By means of Taylor expansions of the molecular SFA, we link this effect to the dynamics of the electron in the continuum. More precisely, we find that the value of the electric field at recombination time plays a crucial role in the shape of the destructive interference phase jump.
关键词： molecular spectroscopy,spectral phase,strong-field approximation,two-center interferences,time-dependent Schr?dinger equation,high-order harmonic generation
更新于2025-09-23 15:23:52
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Broadband molecular spectroscopy with optical frequency combs
摘要： Over the past dozen years, optical frequency combs have evolved into valuable tools for broadband molecular spectroscopy. They have already enabled remarkable advances for the measurement of complicated molecular spectra by improving the resolution, accuracy, sensitivity, and measurement times of spectrometric approaches. In this featured article, we trace some recent developments relevant to high-resolution spectroscopy of molecules, especially in the mid-infrared spectral region. We discuss examples that harness the emerging techniques of cavity-enhanced frequency comb spectroscopy and dual-comb spectroscopy and we conclude with a perspective of forthcoming opportunities and challenges.
关键词： optical frequency combs,molecular spectroscopy,dual-comb spectroscopy,cavity-enhanced frequency comb spectroscopy
更新于2025-09-23 15:21:21
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Controlled Quantum-Dot Formation in Atomically-Engineered Graphene Nanoribbons Field-Effect Transistors
摘要： Graphene nanoribbons (GNRs) have attracted a strong interest from researchers worldwide, as they constitute an emerging class of quantum-designed materials. The major challenges towards their exploitation in electronic applications include reliable contacting, complicated by their small size (< 50 nm), as well as the preservation of their physical properties upon device integration. In this combined experimental and theoretical study, we report on the quantum dot (QD) behavior of atomically precise GNRs integrated in a device geometry. The devices consist of a film of aligned 5-atoms wide GNRs (5-AGNRs) transferred onto graphene electrodes with a sub 5-nm nanogap. We demonstrate that the narrow-bandgap 5-AGNRs exhibit metal-like behavior at room temperature and single-electron transistor behavior for temperatures below 150 K. By performing spectroscopy of the molecular levels at 13 K, we obtain addition energies in the range of 200-300 meV. DFT calculations predict comparable addition energies and reveal the presence of two electronic states within the bandgap of infinite ribbons when the finite length of the 5-AGNRs is accounted for. By demonstrating the preservation of the 5-AGNRs molecular levels upon device integration, as demonstrated by transport spectroscopy, our study provides a critical step forward in the realisation of more exotic GNR-based nano-electronic devices.
关键词： graphene nanoribbons,Coulomb blockade,molecular spectroscopy,device integration,Raman spectroscopy
更新于2025-09-23 15:21:01
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Passive coherent dual-comb spectroscopy based on optical-optical modulation with free running lasers
摘要： Dual-comb spectroscopy is a powerful spectroscopic tool with ultrahigh-resolution, high-sensitivity properties, which opens up opportunities for the parallel detection of multi-species molecules. However, in its conventional form, highly stable laser combs with sophisticated control systems are required to perform dual-comb spectroscopy. Here, a passive mutually coherent dual-comb spectroscopy system via an optical-optical modulation method is addressed, where all fast phase-locking electronics are retired. Without post computer-based phase-correction, a high degree of mutual coherence between the two combs with a relative comb-tooth linewidth of 10 mHz is achieved, corresponding to a coherent time of 100 s. To demonstrate the performance and versatility of the system, the dual comb spectrometer is applied to record the mode-resolved single molecular spectra as well as parallel detected spectra of mixed gases including CO2, CO and C2H2 that well agree with the established spectral parameters. Our technique exhibits flexible wavelength tuning capability in the near-infrared region and can be potentially extended to the mid-infrared region for more applications.
关键词： Optical frequency combs,Molecular spectroscopy,Comb spectroscopy,Optical-optical modulation
更新于2025-09-23 15:19:57
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Infrared attenuated total reflection spectroscopic analysis and quantitative detection of forage spectral features in ruminant systems
摘要： This study aimed to (1) access protein molecular structure profile and metabolic characteristics of model forages [Foreign sourced-origin (coded as: “FSO”, n = 7 vs. Chinese sourced-origin alfalfa hay “CSO”, n = 5] in ruminant systems; (2) Quantify the relationship between forage protein molecular structures and protein utilization and availability. Advanced non-invasive vibrational molecular spectroscopic technique (ATR-FTIR: Attenuated Total Reflection Fourier Transform Infrared spectroscopy) with chemometrics was applied to reveal forage protein molecular structure. Both univariate and multivariate molecular spectral analyses were applied to study molecular structure features in model forages. The molecular structure study provided the detailed protein structure profiles of Amide I and Amide II areas and height, total Amide I and II area ratios, Amide I to II height ratio as well as Amide I to II area ratio using ATR-FTIR spectroscopy. The results showed FSO and CSO had similar (P > 0.05) protein rumen degradation kinetics. However, FSO had superior quality than CSO in intestinal (IDP) and total digestible protein (TDP) and truly absorbed nutrient supply (P < 0.05). As intestinal digestion of protein, FSO was higher (P < 0.05) in protein digestion in terms of: intestinal digestibility of rumen undegraded protein (dIDP: 47.5 vs. 38.3 %RUP); Intestinal digestible protein (IDP: 17.6 vs. 13.7 %CP). As truly absorbed nutrient supply, FSO contained higher (P < 0.05) truly absorbed rumen synthesized microbial protein, absorbable rumen undegradable feed protein in the small intestine, total truly digested protein in the small intestine, metabolizable protein and Feed Milk Value (FMVDVE: 1.2 vs. 1.1 g/kg DM). The molecular structure-nutrition interactive relationship study showed that protein molecular structure profiles were highly associated to protein rumen degradation kinetics, significantly correlated to protein subfractions, protein intestinal digestion, and truly absorbed nutrient supply in ruminant systems.
关键词： Vibrational molecular spectroscopy-ATR-FTIR,Intestine digestion,Model forages,Truly absorbed protein supply,Rumen degradation,Protein molecular structure and conformation,Univariate and multivariate molecular spectral analyses
更新于2025-09-12 10:27:22
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Spatial Molecular AlO Temperature Distributions in Laser-Induced Plasma
摘要： Spatially resolved, line-of-sight measurements of aluminum monoxide emission spectra in laser ablation plasma are used with Abel inversion techniques to extract radial plasma temperatures. Contour mapping of the radially deconvolved signal intensity shows a ring of AlO formation near the plasma boundary with the ambient atmosphere. Simulations of the molecular spectra were coupled with the line profile fitting routines. Temperature results are presented with simultaneous inferences from lateral, asymmetric radial, and symmetric radial AlO spectral intensity profiles. This analysis indicates that shockwave phenomena in the radial profiles, including a temperature drop behind the blast wave created during plasma initiation were measured.
关键词： laser-induced plasma,Abel transform,plasma spectroscopy,molecular spectroscopy,plasma dynamics,laser-induced breakdown spectroscopy,diatomic spectroscopy
更新于2025-09-12 10:27:22
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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) - Computational High-Resolution Dual-Comb Spectroscopy with a Free-Running All-Fiber Laser
摘要： Dual-comb spectroscopy (DCS) has experienced a remarkable growth propelled by recent advances in fiber and semiconductor technology. A key enabler for DCS is mutual stability between two repetition-rate-mismatched frequency combs, which conventionally relies on feedback loops employing additional optics and electronics to synchronize a pair of sources. This limitation can be overcome in several ways, of which one of the most promising is the generation of two frequency combs in a single free-running fiber laser cavity [1–3]. To date, however, the only configuration proven to be compatible with Doppler-limited spectroscopy was the dual-color laser presented in Ref. [2] requiring external spectral broadening, thus adding an extra layer of complexity. Here, we report on the realization of a drastically simplified all-fiber dual-comb laser (AFDCL) with an unprecedentedly low number of components and battery-operation-compatible electrical power consumption (0.35 W) with excellent suitability for spectroscopy of Doppler-limited transitions (Fig. 1). A key feature of our solution relying on polarization-multiplexing [3] is that the laser cavity has an easily adjustable repetition rate difference ranging from sub-kHz to dozens of kHz obtained by varying the intracavity polarization state using polarization controllers (PC) and/or the length of the polarization maintaining fiber in the cavity, which is not possible in the dual-color or bidirectional schemes. Furthermore, we achieve uninterrupted operation times of dozens of hours, and a record-high repetition rate for an AFDCL exceeding 140 MHz to maximize the optical power per comb tooth. High-resolution molecular dual-comb spectroscopy in free-running mode is made possible thanks to a novel real-time compatible phase correction algorithm that marks a radical departure from the cross-correlation or cross-ambiguity function paradigm, hence considerably lowering the complexity of such procedures. As a demonstration, we measure P18-P27 lines of the 2ν3 band of H13C14N at 10 Torr with FWHM Doppler line widths of ~450 MHz within 200 ms (Fig. 1b,c) with better than 1% of precision in a 1 THz bandwidth.
关键词： high-resolution,free-running,molecular spectroscopy,Dual-comb spectroscopy,all-fiber laser
更新于2025-09-11 14:15:04
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Measurement of the variation of electron-to-proton mass ratio using ultracold molecules produced from laser-cooled atoms
摘要： Experimental techniques to manipulate cold molecules have seen great development in recent years. The precision measurements of cold molecules are expected to give insights into fundamental physics. Here we use a rovibrationally pure sample of ultracold KRb molecules to improve the measurement on the stability of electron-to-proton mass ratio μ = me/Mp. The measurement is based upon a large sensitivity coefficient of the molecular spectroscopy, which utilizes a transition between a nearly degenerate pair of vibrational levels each associated with a different electronic potential. Observed limit on temporal variation of μ is 1/μ dμ/dt = (0.30 ± 1.0) × 10?14 year?1, which is better by a factor of five compared with the most stringent laboratory molecular limits to date. Further improvements should be straightforward, because our measurement was only limited by statistical errors.
关键词： cold molecules,electron-to-proton mass ratio,molecular spectroscopy,precision measurements,KRb molecules
更新于2025-09-11 14:15:04
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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) - A 12.6 – 15 μm Mid-IR Source Based on Difference Frequency Generation in Orientation-Patterned GaAs
摘要： Tunable laser sources in the mid-infrared (mid-IR) spectral range have been of great interest for a variety of applications such as molecular spectroscopy and trace gas detection. Difference-frequency generation (DFG) based on nonlinear frequency conversion in nonlinear crystals has been an effective approach to realize tunable mid-IR laser sources [1]. Among nonlinear crystals, orientation-patterned (OP) GaAs has been highly attractive for mid-IR DFG laser sources due to its large nonlinear susceptibility, lack of birefringence, wide transparency range (0.9 – 17 μm), high thermal conductivity, and high laser-damage-threshold [2,3]. Here, we report the generation of broadly tunable mid-IR radiation across 12.65 – 15 μm based on the DFG approach using an OP-GaAs crystal.
关键词： mid-IR,difference-frequency generation,orientation-patterned GaAs,tunable laser sources,molecular spectroscopy,trace gas detection
更新于2025-09-11 14:15:04