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- 摘要
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Photon-recoil spectroscopy: Systematic shifts and nonclassical enhancements
摘要： In photon-recoil spectroscopy, signals are extracted from recoils imparted by the spectroscopy light on the motion of trapped ions as demonstrated by Hempel et al. [C. Hempel et al., Nat. Photon. 7, 630 (2013)] and Wan et al. [Y. Wan et al., Nat. Commun. 5, 3096 (2014)]. The method exploits the exquisite efficiency in the detection of phonons achievable in ion crystals and is thus particularly suitable for species with broad noncycling transitions where detection of fluorescence photons is impractical. Here we develop a theoretical model for the description of photon-recoil spectroscopy based on a Fokker-Planck equation for the Wigner function of the phonon mode. Our model correctly explains systematic shifts due to Doppler heating and cooling as observed in the experiment. Furthermore, we investigate quantum metrological schemes for enhancing the spectroscopic sensitivity based on the preparation and detection of nonclassical states of the phonon mode.
关键词： Wigner function,quantum metrology,Doppler effect,nonclassical states,Fokker-Planck equation,trapped ions,photon-recoil spectroscopy
更新于2025-09-09 09:28:46
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Orientation dependence of electric field induced phase transitions in lead-free (Na <sub/>0.5</sub> Bi <sub/>0.5</sub> )TiO <sub/>3</sub> -based single crystals
摘要： The orientation dependence of the electric field induced strain and phase transitions in 0.92(Na0.5Bi0.5)TiO3-0.06BaTiO3-0.02(K0.5Na0.5)NbO3 (NBT-6BT-2KNN) single crystals has been investigated. The evolution of Raman spectra with electric field reveals that a tetragonal ferroelectric phase is initially induced at E=14kV/cm and completed above E=25kV/cm for [001] oriented single crystals. When the electric field is applied along [111] direction, a partial phase transition from pseudocubic to rhombohedral structure is triggered at E=19kV/cm, which is higher than that for inducing tetragonal ferroelectric phase along [001] direction. Both field-induced phase structures and stability of NBT-6BT-2KNN single crystal are strongly associated with the crystallographic orientations. These results provide a better understanding to the field-induced macroscopic strain in lead-free NBT-based ferroelectrics.
关键词： X-ray diffraction,lead-free ferroelectrics,electric field induced phase transitions,Raman spectroscopy,NBT-based single crystals
更新于2025-09-09 09:28:46
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Using Terahertz Time-Domain Spectroscopy to Discriminate among Water Contamination Levels in Diesel Engine Oil
摘要： Terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 2.0 THz was evaluated for discriminating among water contamination levels (0%, 0.1%, and 0.2%) in diesel engine oil (SAE 15W-40). The absorption coefficient demonstrated potential to discriminate among the three water contamination levels with significant differences among all three levels across the 1.111 to 1.332 THz and 1.669 to 1.934 THz ranges. At each of these frequency ranges, each water contamination level was significantly different from the other two. The 0% water contamination level had the lowest absorption coefficient, while 0.2% water had the highest absorption coefficient. The refractive index demonstrated greater potential to discriminate among water contamination levels with significant differences among all three water levels across the 0.5 to 1.5 THz range. The refractive index of 0% water was the lowest and 0.2% water was the highest across the THz range. Linear regression analysis of the refractive index as a predictor of water contamination level yielded a highly significant equation (p < 0.0001, R2 = 0.99, RMSE = 0.01) when using the refractive indices at 0.5 THz. The refractive indices of these oil samples were promising for discrimination of water contamination. THz spectroscopy should be evaluated for discriminating other engine oil contaminants.
关键词： Terahertz spectroscopy,Diesel,Engine oil,Water contamination
更新于2025-09-09 09:28:46
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[Topics in Current Chemistry Collections] Multidimensional Time-Resolved Spectroscopy || Multidimensional Vibrational Coherence Spectroscopy
摘要： Multidimensional vibrational coherence spectroscopy has been part of laser spec-troscopy since the 1990s and its role in several areas of science has continuously been increasing. In this contribution, after introducing the principals of vibrational coherence spectroscopy (VCS), we review the three most widespread experimen-tal methods for multidimensional VCS (multi-VCS), namely femtosecond stimu-lated Raman spectroscopy, pump-impulsive vibrational spectroscopy, and pump-degenerate four wave-mixing. Focus is given to the generation and typical analysis of the respective signals in the time and spectral domains. Critical aspects of all multidimensional techniques are the challenges in the data interpretation due to the existence of several possible contributions to the observed signals or to opti-cal interferences and how to overcome the corresponding difficulties by exploiting experimental parameters including higher-order nonlinear effects. We overview how multidimensional vibrational coherence spectroscopy can assist a chemist in under-standing how molecular structural changes and eventually photochemical reactions take place. In order to illustrate the application of the techniques described in this chapter, two molecular systems are discussed in more detail in regard to the vibra-tional dynamics in the electronic excited states: (1) carotenoids as a non-reactive system and (2) stilbene derivatives as a reactive system.
关键词： Excited states,Photoisomerization,Multidimensional spectroscopy,Coherence spectroscopy,Vibronic coupling,Ultrafast laser spectroscopy,Raman,Vibrational spectroscopy
更新于2025-09-04 15:30:14
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[Topics in Current Chemistry Collections] Multidimensional Time-Resolved Spectroscopy || Two-Dimensional Resonance Raman Signatures of Vibronic Coherence Transfer in Chemical Reactions
摘要： Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in condensed phase systems. 2DRR spectroscopy is motivated by knowledge of non-equilibrium effects that cannot be detected with traditional resonance Raman spectroscopy. For example, 2DRR spectra may reveal correlated distributions of reactant and product geometries in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this chapter, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide. We show that signatures of "vibronic coherence transfer" in the photodissociation process can be targeted with particular 2DRR pulse sequences. Key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopy techniques are also addressed. Overall, recent experimental developments and applications of the 2DRR method suggest that it will be a valuable tool for elucidating ultrafast chemical reaction mechanisms.
关键词： Coherence transfer,Raman spectroscopy,Multidimensional spectroscopy,Ultrafast spectroscopy,Photodissociation
更新于2025-09-04 15:30:14
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Vibrational Microspectroscopy for Cancer Screening
摘要： Vibrational spectroscopy analyses vibrations within a molecule and can be used to characterise a molecular structure. Raman spectroscopy is one of the vibrational spectroscopic techniques, in which incident radiation is used to induce vibrations in the molecules of a sample, and the scattered radiation may be used to characterise the sample in a rapid and non-destructive manner. Infrared (IR) spectroscopy is a complementary vibrational spectroscopic technique based on the absorption of IR radiation by the sample. Molecules absorb specific frequencies of the incident light which are characteristic of their structure. IR and Raman spectroscopy are sensitive to subtle biochemical changes occurring at the molecular level allowing spectral variations corresponding to disease onset to be detected. Over the past 15 years, there have been numerous reports demonstrating the potential of IR and Raman spectroscopy together with multivariate statistical analysis techniques for the detection of a variety of cancers including, breast, lung, brain, colon, oral, oesophageal, prostate and cervical cancer. This paper discusses the recent advances and the future perspectives in relation to cancer screening applications, focussing on cervical and oral cancer.
关键词： cytology,oral cancer,Raman spectroscopy,FTIR spectroscopy,optical diagnosis,cervical cancer,lasers,screening
更新于2025-09-04 15:30:14
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Tracing the Geographical Origin of Lentils (Lens culinaris Medik.) by Infrared Spectroscopy and Chemometrics
摘要： The feasibility of applying the infrared spectroscopy for the geographical origin traceability of lentils from two different countries (Italy and Canada) was investigated. In particular, lentil samples were analyzed by Fourier transform near- and mid-infrared (FT-NIR and FT-MIR) spectroscopy and then discriminated by applying supervised models, i.e., linear discriminant analysis (LDA) and partial least squares discriminant analysis (PLS-DA). To avoid LDA overfitting, two variable strategies were adopted, i.e., a variable reduction by principal component analysis and a variable compression by wavelet packet transform algorithm. FT-MIR models were more discriminating compared to FT-NIR ones with prediction abilities ranging from 98 to 100% and from 91 to 100% for cross- and external validation, respectively. The combination of the FT-MIR and FT-NIR data did not improve the model performances. These findings demonstrated the suitability of the FT-MIR spectroscopy, in combination with supervised pattern recognition techniques, to successfully classify lentils according to their geographical origin.
关键词： Lentils,FT-NIR spectroscopy,FT-MIR spectroscopy,Partial least squares discriminant analysis,Geographical origin,Linear discriminant analysis
更新于2025-09-04 15:30:14
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Optimizing the Synthesis of Zinc-rich Gallium Zinc Oxynitrides by Combining Co-Precipitation and Moisture-Assisted Nitridation
摘要： ZnO-co-doped GaN is a promising catalyst for photocatalytic overall water splitting in the visible light range. The conventional high-temperature synthesis has the drawback that only low amounts of Zn2+ ions can be incorporated into the GaN:ZnO matrix due to a substantial loss of volatile Zn metal during the nitridation of the binary oxides in flowing NH3. By applying moisture-assisted nitridation of a co-precipitated GaZn precursor under milder conditions it was possible to significantly reduce the Zn loss during nitridation. Using a GaZn precursor with a high Zn content, GaN:ZnO nanoparticles containing high amounts of Zn were obtained. The bandgap was found to decrease nearly linearly with increasing Zn content. Concomitantly, the defect density and structural disorder increased with increasing Zn content.
关键词： Gallium zinc oxynitride,UV/Vis spectroscopy,Co-precipitation,Nitridation,Raman spectroscopy
更新于2025-09-04 15:30:14
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A glassy carbon electrode modified with TiO2(200)-rGO hybrid nanosheets for aptamer based impedimetric determination of the prostate specific antigen
摘要： TiO2(200)-rGO hybrid nanosheets were synthesized starting from TiO2, rGO and NaOH solid powders via a scalable hydrothermal process. The weight ratio of TiO2-GO was found to be crucial on the crystal growth and biosensor properties of the final hybrid nanosheets. They were characterized by means of SEM, FESEM-EDX, XRD, XPS, Raman and FTIR spectroscopies in order to verify the formation of very thin TiO2 anatase nanosheets with an orientation of the anatase crystal structure towards the (200) plane. The free active sites of TiO2 structure and the large surface of the 2D graphene structure strongly facilitate charge transport confirmed by BET-BJH analyses. Compared to pure AuNPs, rGO and TiO2, the hybrid nanosheet modified electrode represents the most sensitive aptasensing platform for the determination of PSA. The detection was based on that the variation of electron transfer resistance (Rct) at the modified electrode surface in a solution containing 3.0 mmol L?1 [Fe(CN)6]3?/4- as a redox probe and 0.1 mol L?1 KCl as supporting electrolyte. The detection limit of the sensor is 1 pg mL?1, and the sensor can be operated up to 30 days. It was applied to the analysis of PSA levels in spiked serum samples obtained from patients with prostate cancer. Data compare well with those obtained by an immunoradiometric assay.
关键词： X-ray photoelectron spectroscopy,Effective surface area,Electrochemical impedance spectroscopy,Aptasensor,Voltammetry,Work function
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Connecting Organic and Physical Chemistry Students with Raman Spectroscopy
摘要： The profile of Raman spectroscopy may be elevated in the undergraduate chemistry curriculum by intentionally tying together students’ experiences in the organic and physical chemistry laboratories. In this way the valuable role Raman spectroscopy can play in structure elucidation is highlighted. The Committee on Professional Training of the American Chemical Society includes the category of optical molecular spectroscopy (e.g., IR, UV-Vis, Raman, and fluorescence spectroscopies) as an option in the panel of instruments required for certification. To the authors’ knowledge there are no Raman spectroscopy experiments that build directly on the analysis of compounds synthesized by students in a prior course for the intended purpose of scaffolding the curriculum. This chapter highlights the roles Raman spectroscopy may play in the determination of molecular structure when used in conjunction with other, more common techniques. Indeed, direct comparison to infrared spectroscopy holds the potential to reinforce that technique and its applications while introducing the study of Raman spectra. A set of three reaction products from electrophilic aromatic substitution, Diels-Alder, and aldol condensation (this including site-specific deuteration) is explored. All of these reactions are currently part of the organic chemistry curriculum. By combining analyses performed in organic chemistry with new laboratories written for the physical chemistry laboratory the authors hope to impress upon undergraduates the value of Raman spectroscopy in a context that builds on their previous experiences with other molecular spectroscopy methods.
关键词： structure elucidation,undergraduate chemistry curriculum,electrophilic aromatic substitution,Diels-Alder reaction,Raman spectroscopy,infrared spectroscopy,deuteration,physical chemistry,aldol condensation,organic chemistry
更新于2025-09-04 15:30:14