Готові списки джерел за темами / Lock-In spectroscopy

Добірка наукової літератури з теми "Lock-In spectroscopy"

Автор: Grafiati
Опубліковано: 29 лютого 2024

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Статті в журналах з теми "Lock-In spectroscopy"

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Koresawa, Hidenori, Kyuki Shibuya, Takeo Minamikawa, Akifumi Asahara, Ryo Oe, Takahiko Mizuno, Masatomo Yamagiwa, et al. "Lock-in-detection dual-comb spectroscopy." OSA Continuum 2, no. 6 (June 12, 2019): 1998. http://dx.doi.org/10.1364/osac.2.001998.

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2

Chernyshov, A. K., and E. A. Chernyshova. "Diode-laser derivative spectroscopy without lock-in amplifier." Physics of Wave Phenomena 19, no. 2 (May 25, 2011): 89–92. http://dx.doi.org/10.3103/s1541308x11020038.

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3

Ball, C. A. B., and A. B. Conibear. "Simulated lock‐in amplifier deep level transient spectroscopy." Review of Scientific Instruments 62, no. 11 (November 1991): 2831–32. http://dx.doi.org/10.1063/1.1142169.

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4

Zhang, Qinduan, Jun Chang, Zhenhua Cong, Zongliang Wang, and Fupeng Wang. "Dual Path Lock-In System for Elimination of Residual Amplitude Modulation and SNR Enhancement in Photoacoustic Spectroscopy." Sensors 18, no. 12 (December 4, 2018): 4255. http://dx.doi.org/10.3390/s18124255.

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A technique for elimination of residual amplitude modulation (ERAM) in photoacoustic spectroscopy based on dual path lock-in was proposed and experimentally demonstrated. There are two lock-in amplifiers, one is for gas concentration demodulation and another for residual amplitude modulation (RAM) measurement by tuning the reference signal in different phases, and then a dual path lock-in technique based on subtraction is applied to RAM removal, improving the second harmonic profile significantly. In this system, the signal to noise ratio (SNR) increases about two times based on our dual path lock-in technique compared to one distributed feedback laser diode (DFB-LD). The system achieved a good linear response (R-square = 0.99887) in a concentration range from 100 ppmv to 2400 ppmv and a minimum detection limit (MDL) of 1.47 ppmv.
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5

Holcomb, M. J., and W. A. Little. "Cascading lock‐in amplification: Application to wavelength modulation spectroscopy." Review of Scientific Instruments 63, no. 12 (December 1992): 5570–75. http://dx.doi.org/10.1063/1.1143383.

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6

Fonsêca, Hugo, Diego Rativa, and Ricardo Lima. "In-Loco Optical Spectroscopy through a Multiple Digital Lock-In on a Linear Charge-Coupled Device (CCD) Array." Sensors 23, no. 16 (August 16, 2023): 7195. http://dx.doi.org/10.3390/s23167195.

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Accurate and reliable measurements of optical properties are crucial for a wide range of industrial and commercial applications. However, external illumination fluctuations can often make these measurements challenging to obtain. This work proposes a new technique based on digital lock-in processing that enables the use of CCD spectrometers in optical spectroscopy applications, even in uncontrolled lighting conditions. This approach leverages digital lock-in processing, performed on each pixel of the spectrometer’s CCD simultaneously, to mitigate the impact of external optical interferences. The effectiveness of this method is demonstrated by testing and recovering the spectrum of a yellow LED subjected to other light sources in outdoor conditions, corresponding to a Signal-to-Noise Ratio of −70.45 dB. Additionally, it was possible to demonstrate the method’s applicability for the spectroscopic analysis of gold nanoparticles in outdoor conditions. These results suggest that the proposed technique can be helpful for a wide range of optical measurement techniques, even in challenging lighting conditions.
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7

Yanju Liu, Jianhui Song, Liang Chen, and Sheng Pan. "Design of Lock-in Amplifier Used on the Photoacoustic Spectroscopy." Journal of Convergence Information Technology 8, no. 6 (March 31, 2013): 942–49. http://dx.doi.org/10.4156/jcit.vol8.issue6.112.

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8

Karami, Mohammad, Zahra Heydarinasab, and Farrokh Sarreshtedari. "Sub-Doppler dichroism as a useful tool in alkali atom hyperfine spectroscopy." Laser Physics 33, no. 12 (October 30, 2023): 125701. http://dx.doi.org/10.1088/1555-6611/ad04c7.

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Abstract Analytical modeling of the sub-Doppler dichroic atomic vapor laser lock error signal shows that the slope of this error signal could be of interest for the identification of transitions in alkali atom hyperfine spectroscopy. Among four D1 line transitions of alkali atoms, the slope sign of the sub-Doppler error signal is different only for the case when the Landé g-factor is negative for both the ground and excited states. The analytical model used, which includes all sublevel transitions, shows very good agreement with the experimental spectroscopy results. The use of this technique allows us to accurately characterize hyperfine transitions in alkali atoms without the need for advanced spectroscopic tools.
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Schlierf, Michael, Felix Berkemeier, and Matthias Rief. "Direct Observation of Active Protein Folding Using Lock-in Force Spectroscopy." Biophysical Journal 93, no. 11 (December 2007): 3989–98. http://dx.doi.org/10.1529/biophysj.107.114397.

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10

Ardekani, Hossein, Ryan L. Wilmington, Mounika Vutukuru, Zhuofa Chen, Ryan Brandt, Anna k. Swan, and Kenan Gundogdu. "Broadband micro-transient absorption spectroscopy enabled by improved lock-in amplification." Review of Scientific Instruments 92, no. 10 (October 1, 2021): 104706. http://dx.doi.org/10.1063/5.0060244.

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Більше джерел

Дисертації з теми "Lock-In spectroscopy"

1

Wang, Yang. "CdS Reflection Coefficient Determination via Photocurrent Spectroscopy." Bowling Green State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1219593815.

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2

Přecechtěl, Vít. "Modul elektrochemické impedanční spektroskopie pro výzkum vodíkových palivových článků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221186.

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This thesis deals with diagnostic fuel-cell parameters using electrochemical impedance spectroscopy. The document begins with brief explanation of fuel-cell operation and its basic principles. Thesis continues with description of fuel-cell voltage generation and influence of charge dual-layer on impedance. After that electrochemical impedance spectroscopy, signals used for perturbation and evaluation of impedance spectrum using Bode a Nyquist plot is described. Next part explains measurement of impedance spectrum using potentiostat in combination with lock-in amplifier or frequency response analyzer. Practical part of thesis is dedicated to electric circuit design of EIS module and software designed for automatic measurement of impedance spectrum. Last part shows results of EIS module testing.
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3

Wang, Gaoxuan. "Development of photonic instruments for measurement of aerosol optical properties." Thesis, Littoral, 2018. http://www.theses.fr/2018DUNK0470.

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À cause de leur diffusion et de leur absorption des radiations solaires, les aérosols atmosphériques jouent un rôle important dans l'évolution du climat terrestre. Les techniques de mesure actuelles apportent certes, des connaissances, sur le forçage radiatif mais les résultats possèdent généralement de larges incertitudes, souvent du même ordre de grandeur que la valeur elle-même. Ces incertitudes sont causées par le manque de précision sur les données liées aux propriétés optiques estimées de ces aérosols (comme l'absorption, la diffusion ou l'extinction). Elles découlent principalement des techniques de mesures actuelles : à l'effet de chargement des filtres (lors de mesures classiques par filtres), aux mesures limitées par l'étendue spectrale des instruments, aux conditions d'échantillonnage différents lors de mesures séparées, etc. Dans ce travail de thèse, j'ai développé puis testé des instruments optiques et électroniques dans le but d'augmenter la précision des mesures des coefficients d'extinction et d'absorption des aérosols. (1) Deux spectrophones PhotAccoustique (PA) sont développés afin d'améliorer les mesures d'absorption des aérosols grâce à des mesures directes et sans filtres. Une première génération utilisant un rayonnement à 444 nm permet de réduire les incertitudes de mesure de 20-30% (obtenue par la technique d'échantillonnage par filtres) à 7,4% et 4,6% pour la détermination des coefficients d'absorption massique du carbone suie et de cendres volcaniques, respectivement. Transformé en spectrophone PA à multi-longueurs d'onde opérant conjointement à 444,532 et 660 nm, il permet alors de caractériser la dépendance spectrale du Coefficient d'Absorption d'Ångström (CAA). Les valeurs du CAA du carbone suie sont en accord avec les résultats publiés. Celles obtenues lors de l'analyse de deux échantillons de cendres volcaniques résultant de l'éruption du Eyjafjallajökull sont similaires au CAA du carbone brun,prouvent la présence d'importantes quantités d'éléments organiques. (2) Un extinctiomètre, basé sur le principe de la spectroscopie d'absorption en cavité à source large bande et incohérente (IBBCEAS), est ensuite développé afin de suivre l'évolution des propriétés optiques d'Aérosols Organiques Secondaires (AOS) produits par la photolyse du 2-nitrophénol dans une chambre de simulation atmosphérique de l'University College de Cork (Irlande). Leurs coefficients d'extinction et d'absorption sont suivis par cet extinctiomètre et un spectrophone PA durant tout le processus de production. Les évolutions des propriétés optiques des AOS confirment l'effet du vieillissement atmosphérique. (3) Une nouvelle architecture de détection synchrone est développé afin de rendre notre prototype plus léger, plus compact, mieux adapté aux applications in situ et plus particulièrement aux drones, techniques émergentes qui permettent de caractériser le profil vertical des aérosols dans l'atmosphère. Cette détection synchrone innovante, évaluée lors de la mesure de la concentration de NO₂ ambiant (niveau de concentration de quelques ppbv) possède une précision et une reproductibilité de mesures comparable à la détection synchrone SR830, commercialisée par la société Stanford Research Inc. L'évaluation précise de l'impact climatique des aérosols nécessite une quantification exacte et non biaisée de leurs propriétés optiques. À ce jour, elle reste un défi majeur dans la recherche sur les sciences de l'atmosphère et du changement climatique. Ainsi, des informations sur la taille des particules (liée à l'absorption sélective en longueur d'onde) nécessitent des mesures étendues sur de larges régions spectrales du rayonnement solaire principale. Le développement d'un albédomète large bande à haute précision, dédié à la mesure simultanée des coefficients d'extinction et d'absorption des aérosols est en cours
Atmospheric aerosols are known to play an important role in earth climate by scattering and absorbing solar radiation. However, the aerosol radiative forcing effect is still known with large uncertainties (almost equal to the magnitude of the aerosol radiative forcing). The uncertainties are mainly caused by inaccurate estimates of aerosol optical properties (such as its absorption, scattering and extinction coefficients) using the currently available measurement techniques, with result in filter loading effect in classic filter technique, the uncertainty due to different sampling conditions for separate measurements of aerosol optical properties in combination of different techniques or due to the measurements at limited spectral wavelength ranges. My PhD work was carried out on the developments and applications of optical and electronic instruments for accurate measurements of aerosol extinction and absorption coefficient : (1) Photoacoustic spectrophones were developed for filter-free direct measurements of aerosol absorption with high accuracy. Measurements uncertainties down to about 7.4% and 4.6% (compared to about 20-30% in filter-based measurements) were achieved for the determination of mass absorption coefficients of black carbon and volcanic ash samples, respectively, using a single-wavelength PA spectrophone operating at 444 nm. A 3-wavelength PA spectrophone operating at 444,532 and 660 nm was developed and deployed for characterizing wavelength-dependent optical properties of aerosol absorption Ångström coefficient (AAC). The determined AAC of black carbon was well consistent with the previously reported value. Our AAC values of two volcanic ash samples from 2010 eruptions of Eyjafjallajökull, similar to the AAC of brown carbon, indicated abundant organic compounds in the volcanic ash samples. The developed multi-wavelength PA spectrophone was tested and validated in an intensive field campaign measurements of environmental particles in Grenoble (France). Side-by-side inter-comparison measurements using an aethalometer showed a lineat correlation of the measured aerosol absorption coefficients from both instruments. (2) An extinctiometer based on IBBCEAS was developed for study of optical properties of secondary organic aerosol (SOA) produced from photolysis of 2-nitrophenol in an atmospheric simulation chamber at University College Cork (Ireland). Simultaneous monitoring of the SOA extinction and absorption (in conjuction with a PA spectrophone) coefficients was performed during its whole production process, the measured evolutions of the SOA optical properties highlighted the atmospheric aging effect. (3) In order to render optical sensor lightweight and suitable for field applications, in particular for the newly emerging unmanned aerial vehicle (UAV) applications, a novel architecture of lock-in amplifier (LIA) was proposed and developed in the framework of this Phd Research. The novel LIA, evaluated with an inter-comparison measurement of ambient NO₂ at the ppbv concentration level, shows an identical performance (in terms of measurements accuracy and precision) as the widely used commercial LIA (SR830, Stanford Research Inc.), while using a simplified and lightweight hardware architecture. Evaluation of the aerosol impact on climate requires accurate and unbiased quantification of the its wavelength-dependent optical properties over a wide spectral region of the major solar radiation, which can provide information on particle size (due to the wavelength dependence of scattering by fine particles) as well as insights on aerosol chemical composition (because of its wavelength selective absorption). To date, it is still a key challenge in atmospheric science and climate change research. Development of a broadband aerosol albedometer is ongoing, which is dedicated to simultaneous measurements of aerosol extinction and absorption coefficients with high-accuracy and high-precision
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4

Garcia, Marine. "Développement d’une plateforme d’imagerie pour la caractérisation du transfert de masse dans les microsystèmes : application aux piles à combustible microfluidiques." Electronic Thesis or Diss., Paris, HESAM, 2024. http://www.theses.fr/2024HESAE007.

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Анотація:
Les piles à combustible sont des dispositifs qui transforment l'énergie stockée dans un oxydant et un réducteur en électricité grâce à des réactions électrochimiques. La technologie la plus mature pour réaliser cette conversion est la pile à hydrogène à membrane échangeuse de protons (PEMFC), mais d'autres systèmes alternatifs émergent. En particulier, les piles à combustible microfluidiques (PCM) ont permis de s’affranchir des problématiques liées à l’utilisation d’une membrane et du stockage gazeux grâce à l’utilisation de réactifs liquides à température et pression ambiante. Les dimensions du canal (1-5 mm de large et 20-100 µm de haut) permettent un écoulement co-laminaire des deux réactifs et de l’électrolyte liquides dans un micro-canal contenant les électrodes. Les PCMs n'ont donc pas de membrane et leurs performances sont dirigées par le transport de charges et de masse.À ce jour, il est difficile de caractériser expérimentalement tous les phénomènes physiques qui ont lieu dans la PCM car les méthodes existantes sont plutôt basées sur la caractérisation électrochimique. Ces méthodes permettent d'avoir une caractérisation globale du système mais ne fournissent pas d'informations précises sur les phénomènes de transport de masse dans le canal. Pour étudier le transport de masse, la modélisation numérique est généralement utilisée et permet de simuler le champ de concentration et les performances de la PCM pour différentes architectures et conditions opératoires. Toutefois, l'utilisation de ces modèles repose sur la connaissance de paramètres in-situ tels que le coefficient de diffusion D et le coefficient de réaction k0. Dans les travaux numériques, ces paramètres sont généralement approximés, ce qui permet une appréhension plutôt qualitative des phénomènes de transport. De plus, ces études numériques n'ont à ce jour pas été vérifiées avec des études expérimentales.Ainsi, le principal verrou scientifique de cette thèse repose sur le développement de méthodes d'imagerie quantitatives pour la caractérisation du champ de concentration dans une PCM en fonctionnement.Pour répondre à ce besoin, une plateforme d'imagerie basée sur la spectroscopie ainsi que trois méthodes de caractérisation ont été développées dans cette thèse. Dans un premier temps, les travaux se sont concentrés sur le développement d'un banc de spectroscopie pour étudier le phénomène d'interdiffusion. Cette étude a permis d'estimer le coefficient de diffusion du permanganate de potassium dans l'acide formique. Ces solutions ont été spécifiquement choisies car ceux sont celle utilisées dans la PCM développées pour la suite de l’étude.Le banc de spectroscopie a ensuite été adapté pour étudier le champ de concentration 2D en régime permanent d'une PCM en fonctionnement. Un modèle analytique du transfert de masse (advection/réaction/diffusion) couplé au champ de concentration 2D a ainsi permis de déterminer le taux de réaction. Les variations de concentration mises en jeu étant parfois très faibles (quelques micro-moles), une autre technique de caractérisation a été mis en place pour diminuer le bruit de mesure.Afin d'améliorer le rapport signal sur bruit, une méthode basée sur la modulation du champ de concentration a été développée. La démodulation du signal a permis de réduire significativement le bruit et des concentrations de 20 µM ont ainsi été estimées. Un modèle analytique décrivant le champ modulé a été établi afin d'implémenter une méthode inverse. La méthode proposée a permis de retrouver le taux de réaction associé à la variation de concentration.En conclusion, les méthodes de caractérisation proposées dans cette thèse permettent d'estimer quantitativement le transfert de masse et la cinétique de réaction à partir du champ de concentration 2D d'une PCM en fonctionnement. Cette technique a été appliquée au PCM, mais elle peut être transférée à un système micrométrique dans lequel les phénomènes de diffusion-advection-réaction ont lieu
Fuel cells are devices that convert the energy stored in an oxidant and a reductant into electricity through electrochemical reactions. The most mature technology for this conversion is the proton exchange membrane fuel cell (PEMFC), but other alternative systems are emerging. In particular, microfluidic fuel cells (MFCs) have overcome the problems associated with the use of a membrane and gas storage by using liquid reagents at ambient temperature and pressure. The dimensions of the channel (1-5 mm wide and 20-100 µm high) allow co-laminar flow of the two liquid reagents and the electrolyte in a microchannel containing the electrodes. Therefore, PCMs do not need membrane to separate reactants and performances are driven by charge and mass transport.Experimental characterization of all the physical phenomena involved in PCMs is difficult because actuals methods are more based on electrochemical characterisation. These methods provide an overall characterisation of the system but they do not give precise information on the mass transport phenomena occurring in the channel. To investigate concentration field, numerical modelling is generally used. Numerical methods evaluate the impact of the geometry or the operating conditions on MFC performances. However, the use of these models relies on the knowledge of in-situ parameters such as the diffusion coefficient D and the reaction rate k0. In numerical studies, these parameters are generally approximated leading to a qualitative understanding of the transport phenomena. Furthermore, these numerical studies have not yet been verified by experimental studies.Thus, the main scientific challenge of this thesis is to develop quantitative imaging methods for characterising the concentration field in an operating PCM.To meet this need, an imaging platform based on spectroscopy and three characterisation methods were developed in this thesis. First of all, the work focused on developing an experimental setup based on spectroscopy to study the interdiffusion phenomenon. This study reports the estimation of the diffusion coefficient of potassium permanganate in formic acid. These solutions were specifically chosen because they are used in the PCM developed for the rest of the study.The imaging plateform was then adapted to study the in operando MFC 2D concentration field in steady-state. An analytical mass transfer model (advection/reaction/diffusion) coupled to the 2D concentration field was used to determine the reaction rate. As the concentration variations involved can be very small (few micro-moles), another characterisation technique was implemented to reduce the measurement noise.To improve the signal-to-noise ratio, a method based on modulation of the concentration field was developed. Demodulation of the signal significantly reduced the noise and concentrations of 20 µM were estimated. An analytical model describing the modulated field was established in order to implement an inverse method. The proposed method made it possible to recover the reaction rate associated with the concentration variation.To conclude, the proposed characterisation methods enable the estimation of the mass transfer and the reaction kinetics using the 2D concentration field from an in operando MFC. This technique has been applied to the MFC, but it can be transferred to a micrometric system in which diffusion-advection-reaction phenomena take place
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5

Vieillard, Thomas. "Dynamique induite par champ laser femtoseconde intense : alignement moléculaire en milieu gazeux dense et effet Kerr." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00697019.

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Le sujet de cette thèse concerne l'étude de dynamiques induites par des impulsions lasers femtosecondes intenses. La première dynamique étudiée porte sur l'alignement de la molécule de CO2, pure ou en mélange avec l'argon ou l'hélium, en phase gazeuse dense (jusqu'à 20 bar), ce régime n'ayant jamais été étudié expérimentalement auparavant. L'alignement moléculaire, quand il est induit par une impulsion laser femtoseconde et intense, présente deux contributions qui apparaissent après passage de l'impulsion : un alignement permanent et un alignement transitoire. L'influence des collisions se manifeste alors par des transferts de population entre états rotationnels qui ont pour conséquence de faire décroître ces deux contributions. Le temps de décroissance de l'alignement permanent est seulement lié aux collisions inélastiques tandis que le temps de décroissance de l'alignement transitoire est lié à la fois aux collisions inélastiques et élastiques. Nous montrons alors que la détermination expérimentale de la contribution des collisions élastiques, expérimentalement difficile d'accès, est possible à partir de l'analyse des traces d'alignement moléculaire. Cette analyse se base sur la modélisation des taux de transfert entre états liés aux collisions inélastiques par des lois semi-empiriques du type ECS-(E)P. La contribution élastique des collisions déterminée est en bon accord avec des valeurs calculées selon un modèle classique. La deuxième dynamique étudiée est la dépendance en éclairement de l'effet Kerr électronique. Nous poursuivons alors les travaux menés par Loriot et al. en 2009 qui ont montré que l'indice Kerr électronique saturait avant de s'annuler puis de présenter une contribution négative lorsqu'on augmente l'éclairement (inversion du signe pour quelques dizaines de térawatts par centimètre carré). Nous avons alors étendu cette étude en observant à une longueur d'onde de 400 nm (800 nm dans l'étude originale) cette inversion du signe de l'indice Kerr dans l'air.
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6

Peronio, Angelo. "A closer look at heterogeneous catalysis: reaction intermediates at the single-molecule level." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8577.

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Анотація:
2011/2012
The present work pertains to the surface science approach to heterogeneous catalysis. In particular model systems for CO2 hydrogenation to methanol, and NO selective catalytic reduction, are investigated by means of a combined approach, where the molecular-level insight provided by a low-temperature scanning tunneling microscope is complemented by density functional theory (DFT) calculations of their electronic structure. To this end, the Inelastic Electron Tunneling Spectroscopy (STM-IETS) technique was introduced for the first time in our laboratory, a recent development which allows to measure the vibrational spectrum of individual molecules adsorbed on a surface. Regarding CO2, we provide single molecule imaging and characterization of CO2/Ni(110), chemisorbed with high charge transfer from the substrate, in an activated state that plays a crucial role in the hydrogenation process. We obtain a detailed characterization of the adsorption geometries and an estimate of the energies corresponding to the different adsorbed states. A consistent picture of CO2 chemisorption on Ni(110) is provided on the basis of the newly available information, yielding a deeper insight into the previously existing spectroscopic and theoretical data. In the Selective Catalytic Reduction (SCR) process, nitrogen oxide is selectively transformed to N2 by reductants such as ammonia. The specificity of this reaction was tentatively attributed to the formation of NH3-NO coadsorption complexes, as indicated by several surface science techniques. Here we characterize the NH3-NO complex at the atomic scale on the (111) surface of platinum, investigating the intermolecular interactions that tune the selectivity. The structures that arise upon coadsorption of NH3 and NO are analyzed in terms of adsorption sites, geometry, energetics and charge rearrangement. An ordered 2 × 2 adlayer forms, where the two molecules are arranged in a configuration that maximizes mutual interactions. In this structure, NH3 adsorbs on top and NO on fcc-hollow sites, leading to a cohesional stabilization of the extended layer by 0.29 eV/unit cell. The calculated vibrational energies of the individually-adsorbed species and of the coadsorption structure fit the experimental values found in literature within less than 6%. The characterizations and optimizations that had to be tackled in order to successfully perform STM-IETS measurement are eventually presented, focusing in particular on an original method which allows to increase the achieved resolution. Namely, the modulation broadening associated to phase-sensitive detection is reduced by employing a tailored modulation function, different from the commonly-used sinusoid. This method is not limited to STM-IETS, but can be easily applied whenever a lock-in amplifier is used to measure a second derivative.
XXV Ciclo
1984
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7

Karthik, G. "Investigations Of Spin-Dynamics And Steady-States Under Coherent And Relaxation Processes In Nuclear Magnetic Resonance Spectroscopy." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/259.

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The existence of bulk magnetism in matter can be attributed to the magnetic properties of the sub-atomic particles that constitute the former. The fact that the origin of these microscopic magnetic moments cannot be related to the existence of microscopic currents became apparent when this assumption predicted completely featureless bulk magnetic properties in contradiction to the observation of various bulk magnetic properties [1]. This microscopic magnetic moment, independent of other motions, hints at the existence of a hitherto unknown degree of freedom that a particle can possess. This property has come to be known as the "spin" of the particle. The atomic nucleus is comprised of the protons and the neutrons which possess a spin each. The composite object- the atomic nucleus is therefore a tiny magnet itself. In the presence of an external bias like a magnetic field, the nucleus therefore evolves like a magnetic moment and attains a characteristic frequency in its evolution called the Larmor frequency given by, (formula) where η is the magnetogyric ratio of the particle and B is the applied magnetic field. The existence of a natural frequency presents the possibility of a resonance behaviour in the response of the system when probed with a driving field. This is the basic principle of magnetic resonance, which in the context of the atomic nucleus, was discovered independently by Purcell [2] and Bloch [3]. From its conception, the technique and the associated understanding of the involved phenomena have come a long way. In its original form the technique involved the study of the steady-state response of the nuclear magnetic moment to a driving field. This continuous wave NMR had the basic limitation of exciting resonances in a given sample, serially. In due course of time, this technique was replaced by the Fourier transform NMR (FTNMR) [4]. This technique differed from the continuous wave NMR in its study of the transient response of the system in contrast to the steady-state response in the former. The advantage of this method is the parallel observation of all the resonances present in the system ( within the band-width of the excitation). In addition to the bias created by the external field, other internal molecular fields produce additional bias which in turn produce interesting signatures on the spectrum of the system, which are potential carriers of information about the molecular state. The fact that the spins are not isolated from the molecular environment, produces a striking effect on the ideal spectrum of the system. These effects contain in them, the signatures of the molecular local environment and are hence of immense interest to physicists, chemists and biologists.
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8

Karthik, G. "Investigations Of Spin-Dynamics And Steady-States Under Coherent And Relaxation Processes In Nuclear Magnetic Resonance Spectroscopy." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/259.

Повний текст джерела
Анотація:
The existence of bulk magnetism in matter can be attributed to the magnetic properties of the sub-atomic particles that constitute the former. The fact that the origin of these microscopic magnetic moments cannot be related to the existence of microscopic currents became apparent when this assumption predicted completely featureless bulk magnetic properties in contradiction to the observation of various bulk magnetic properties [1]. This microscopic magnetic moment, independent of other motions, hints at the existence of a hitherto unknown degree of freedom that a particle can possess. This property has come to be known as the "spin" of the particle. The atomic nucleus is comprised of the protons and the neutrons which possess a spin each. The composite object- the atomic nucleus is therefore a tiny magnet itself. In the presence of an external bias like a magnetic field, the nucleus therefore evolves like a magnetic moment and attains a characteristic frequency in its evolution called the Larmor frequency given by, (formula) where η is the magnetogyric ratio of the particle and B is the applied magnetic field. The existence of a natural frequency presents the possibility of a resonance behaviour in the response of the system when probed with a driving field. This is the basic principle of magnetic resonance, which in the context of the atomic nucleus, was discovered independently by Purcell [2] and Bloch [3]. From its conception, the technique and the associated understanding of the involved phenomena have come a long way. In its original form the technique involved the study of the steady-state response of the nuclear magnetic moment to a driving field. This continuous wave NMR had the basic limitation of exciting resonances in a given sample, serially. In due course of time, this technique was replaced by the Fourier transform NMR (FTNMR) [4]. This technique differed from the continuous wave NMR in its study of the transient response of the system in contrast to the steady-state response in the former. The advantage of this method is the parallel observation of all the resonances present in the system ( within the band-width of the excitation). In addition to the bias created by the external field, other internal molecular fields produce additional bias which in turn produce interesting signatures on the spectrum of the system, which are potential carriers of information about the molecular state. The fact that the spins are not isolated from the molecular environment, produces a striking effect on the ideal spectrum of the system. These effects contain in them, the signatures of the molecular local environment and are hence of immense interest to physicists, chemists and biologists.
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9

Jarvis, Thomas William. "Novel tools for ultrafast spectroscopy." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-12-4456.

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Exciton dynamics in semiconductor nanostructures are dominated by the effects of many-body physics. The application of coherent spectroscopic tools, such as two-dimensional Fourier transform spectroscopy (2dFTS), to the study of these systems can reveal signatures of these effects, and in combination with sophisticated theoretical modeling, can lead to more complete understanding of the behaviour of these systems. 2dFTS has previously been applied to the study of GaAs quantum well samples. In this thesis, we outline a precis of the technique before describing our own experiments using 2dFTS in a partially collinear geometry. This geometry has previously been used to study chemical systems, but we believe these experiments to be the first such performed on semiconductor samples. We extend this technique to a reflection mode 2dFTS experiment, which we believe to be the first such measurement. In order to extend the techniques of coherent spectroscopy to structured systems, we construct an experimental apparatus that permits us to control the beam geometry used to perform four-wave mixing reflection measurements. To isolate extremely weak signals from intense background fields, we extend a conventional lock-in detection scheme to one that treats the optical fields exciting the sample on an unequal footing. To the best of our knowledge, these measurements represent a novel spectroscopic tool that has not previously been described.
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Частини книг з теми "Lock-In spectroscopy"

1

MESSERLE, BARBARA A., GERHARD WIDER, GOTTFRIED OTTING, CHRISTOPH WEBER, and KURT WÜTHRICH. "Solvent Suppression Using a Spin Lock in 2D and 3D NMR Spectroscopy with H2O Solutions." In NMR in Structural Biology, 411–16. WORLD SCIENTIFIC, 1995. http://dx.doi.org/10.1142/9789812795830_0033.

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2

Otting, Gottfried. "Chapter 8 Use of high power spin-lock purge pulses in high resolution NMR spectroscopy." In Methods for Structure Elucidation by High-Resolution NMR Applications to Organic Molecules of Moderate Molecular Weight, 149–71. Elsevier, 1997. http://dx.doi.org/10.1016/s0926-4345(97)80010-7.

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3

Lesot, Philippe, and Olivier Lafon. "Combining Fast 2D NMR Methods and Oriented Media." In Fast 2D Solution-state NMR, 441–75. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/bk9781839168062-00441.

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NMR in oriented samples (anisotropic solvents) offers access to informative residual order-dependent NMR interactions, including chemical shift anisotropies (RCSAs), dipolar couplings (RDCs), and quadrupolar couplings (RQCs), while preserving high spectral resolution. The analysis of these spectra often requires two-dimensional (2D) NMR experiments due to these additional anisotropic interactions. In addition, accelerated 2D NMR experiments can be essential for particular investigations, including in situ monitoring of chemical reactions or the observation of dilute isotopes, e.g. 2H and 13C, since the stability of oriented phases is limited in time and the magnetic field, B0, can drift in the absence of 2H lock. We provide here an overview of these fast 2D NMR experiments in anisotropic media. These developments have benefited from those for isotropic solutions, such as fast pulsing techniques enhancing the polarization, sparse sampling, Hadamard spectroscopy or spatial encoding. Nevertheless, fast 2D NMR in mesophases and solids present particular challenges, since these 2D spectra usually display lower signal-to-noise ratios, non-Lorentzian lineshapes, lower spectral resolution and wider spectral widths than their counterparts for isotropic solutions. We discuss here the advantages and limitations of various approaches, which have been applied for the fast 2D NMR spectra of mesophases and solids.
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Тези доповідей конференцій з теми "Lock-In spectroscopy"

1

Koresawa, Hidenori, Kyuki Shibuya, Akifumi Asahara, Takeo Minamikawa, Kaoru Minoshima, and Takeshi Yasui. "Use of Lock-in Detection in Dual-Comb Spectroscopy." In Fourier Transform Spectroscopy. Washington, D.C.: OSA, 2018. http://dx.doi.org/10.1364/fts.2018.jt2a.26.

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2

Stremplewski, Patrycjusz, Justyna Grzelak, Magdalena Twardowska, Ireneusz Grulkowski, Sebastian Mackowski, and Maciej Wojtkowski. "Dual Optical Lock-In for Ultrasensitive Photothermal Effect Detection." In Optical Tomography and Spectroscopy. Washington, D.C.: OSA, 2016. http://dx.doi.org/10.1364/ots.2016.otu4c.7.

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3

Song, Wuzhou, and Demetri Psaltis. "Optofluidic lock-in spectroscopy on a chip." In CLEO: Science and Innovations. Washington, D.C.: OSA, 2011. http://dx.doi.org/10.1364/cleo_si.2011.ctuf1.

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4

De Oliveira Lima, Bernardo Caio Nunes, Ricardo Ataíde De Lima, and Eduardo Fontana. "Microcontrolled Lock-In Amplifier for Spectroscopy Applications." In 2023 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC). IEEE, 2023. http://dx.doi.org/10.1109/imoc57131.2023.10379736.

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5

ZHANG, Lijuan, Shizhe CHEN, Yushang WU, Xianglong YANG, Qiang ZHAO, Kai WANG, Shixuan LIU, and Keke Zhang. "Application of digital quadrature lock-in amplifier in TDLAS humidity detection." In Optical Spectroscopy and Imaging, edited by Tsutomu Shimura, Mengxia Xie, Bing Zhao, Jin Yu, Zhe Wang, Wei Hang, and Xiandeng Hou. SPIE, 2017. http://dx.doi.org/10.1117/12.2281751.

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6

Nadgir, Amrut, Niranjan Shivaram, Matthew Brister, Richard Thurston, and Daniel Slaughter. "SOFTWARE IMPLEMENTATION OF A MULTI-CHANNEL, MULTI-FREQUENCY LOCK-IN AMPLIFIER." In 2021 International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2021. http://dx.doi.org/10.15278/isms.2021.wb12.

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7

Koresawa, Hidenori, Kyuki Shibuya, Akifumi Asahara, Takeo Minamikawa, Kaoru Minoshima, and Takeshi Yasui. "Combination of Lock-in Detection with Dual-Comb Spectroscopy." In CLEO: Applications and Technology. Washington, D.C.: OSA, 2019. http://dx.doi.org/10.1364/cleo_at.2019.jth2a.101.

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8

Koresawa, Hidenori, Kyuki Shibuya, Takeo Minamikawa, Akifumi Asahara, Kaoru Minoshima, and Takeshi Yasui. "Combination of lock-in detection with dual-comb spectroscopy." In Photonic Instrumentation Engineering VI, edited by Yakov G. Soskind. SPIE, 2019. http://dx.doi.org/10.1117/12.2509619.

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9

Ragni, A., G. Sciortino, M. Sampietro, G. Ferrari, F. Crisafi, V. Kumar, and D. Polli. "Lock-In Based Differential Front-End For Raman Spectroscopy Applications." In 2018 14th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME). IEEE, 2018. http://dx.doi.org/10.1109/prime.2018.8430339.

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10

Fonseca, Hugo, Ricardo Lima, and Diego Rativa. "A Software-Based Lock-in Amplifier for Optical Spectroscopy Applications." In 2022 SBFoton International Optics and Photonics Conference (SBFoton IOPC). IEEE, 2022. http://dx.doi.org/10.1109/sbfotoniopc54450.2022.9992701.

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