Laser Spectroscopy

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Applications of laser spectroscopy in nuclear research and industry Applications of laser spectroscopy in space and environmental applications. Laser Spectroscopy for Sensing: Fundamentals, Techniques and Applications, Second Edition, examines the latest advances in laser spectroscopy and its use in a diverse range of industrial, medical and environmental applications.

The book provides an overview of laser spectroscopy at three levels, including the fundamental aspects to consider when planning use of laser spectroscopy to solve a problem from the sample properties to the laser properties to the data analysis , the technical aspects of several spectroscopic techniques, and the fields of applications of such techniques. New sections include key advancements from the field and chapters surrounding Raman Spectroscopy and Laser-induced breakdown spectroscopy.

His panel covers the fundamentals of laser-induced plasmas, the application of laser spectroscopies such as LIBS, Fluorescence, Raman, FTIR, as fundamental diagnostics as well as sensing techniques for defense, industrial, environmental, biomedical applications and the study of propagation of ultrashort laser pulses for sensing purposes at distances up to the kilometer range. A large part of his research focuses also on the quantification of interferences in spectroscopic signals.

We are always looking for ways to improve customer experience on Elsevier. We would like to ask you for a moment of your time to fill in a short questionnaire, at the end of your visit. If you decide to participate, a new browser tab will open so you can complete the survey after you have completed your visit to this website. Thanks in advance for your time. Skip to content. Search for books, journals or webpages All Pages Books Journals. Editors: Matthieu Baudelet. Paperback ISBN: Imprint: Woodhead Publishing. Published Date: 1st December Page Count: Two types of procedures were used for HE deposition.

In the second procedure, a metallic tip was pressed against a deposit of HE, and small quantities particles of the HE were transferred to the tip. Then these particles were deposited onto the fabrics. The fabrics were weighted before and after the transfer of the HEs to know the quantities deposited. Mass measurements were done using two scales.

The first scale used for depositions of 3—0. CLS can be considered as the transition between univariate and multivariate procedures of analysis. It is the most used regression method in academic environments since it is based on the Beer-Lambert—Bouguer linear relationship between the absorbance of a chemical species in a mixture of a solute and solvent, the path length of the light through the cell containing the mixture and the molar concentration of the species.

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Its familiarity among practitioners and students is based on the fact that for dilute solutions, it is directly applicable to quantitative spectral analyses [ 58 ]. CLS analysis can be easily extended to multi-component systems, where a wide range of peaks of several components in a mix is involved in the study.

Typically, comprehensive information of the discrete constituents in the matrix studied is essential. This requirement is the greatest limitation of the regression analysis algorithm. Thus, the spectrum of each of the neat component as well as the spectrum of the mix is required to be able to estimate the spectral portion of each constituent in the mix. This is correct only when pure constituents are involved.

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The intensity at any wavenumber can be treated as a linear arrangement of the intensities of each constituent in the mix. The technique also estimates the portion of each spectrum constituent in the spectrum of the mix by minimizing the sum of the squares of the errors. Typically, this is equal to or linearly related to the percentage in the mix. Two components, three components, and four components mixes were made from the four 4 constituents in the calibration set: three explosives: TNT, RDX, PETN, and the substrates: cotton, synthetic fabric or a mixed fabric.

CLS analysis was coupled to QCL reflectance measurements of the four components and their mixes with the objective of developing a methodology for fast detection and discrimination analysis HE on fabrics. A simple technique for visualization of the data and interpretation of the models is presented. PLS-DA-based analysis requires the generation of independent models for each fabric type.

In the proposed CLS application, adapting the models to field work requires adding the spectra of new HEs or new substrates types to the database. QCL diffuse reflectance spectra of all components and mixes were acquired using a rough gold substrate as background reference. Figure 5 contains typical spectra obtained for the HEs and the fabrics. Normalization of the spectral data was achieved using SNV as preprocessing algorithm, applied to the whole spectroscopic range studied to remove the baseline drifts caused by scattering based on variations in particle size of the analytes HEs and the morphology of the substrates.

PLS Toolbox v. Other statistical routines were implemented using Statgraphics Centurion XV software, version Statpoint Technologies, Inc. The linear model based on CLS can be described by [ 58 ].

It has been assumed that there are no interactions among the components in the mix leading to chemical bonds. If present, these interactions would result in changes in intensities, shifts of band locations and formation or loss of vibrational bands due to the chemical bonds formed. Thus, at least to first order, the contributions to a given intensity are additive. The signals of interest for each constituent of the mix can be extracted from the model.

Three types of CLS models were created, according to the constituents in the mix: 2, 3, and 4-constituent models. One of the binary models consisted only in spectra of the fabric and one of the HEs. Thus, Eq. A total of 12 samples containing surface loadings of HEs in the range of 0.

Probability distributions were then predicted. The p-values of the models were used as decision thresholds. This implies that there is a high probability that non-dosed substrates were below the threshold.

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To obtain good discrimination typical spectra of the fabric substrates were required to be present in the database. As shown in Table 2 , the models generated were characterized with high selectivity and sensitivity for the HEs in the range of 0. Figure 5 shows the estimation of the probability for TNT in the range of 0.

The spectra for the two-component models for the HEs are shown in Figure 6a — c. Predicted spectra from Eq. The two-components model that consists of cotton fabric and RDX spectra is shown as an example. The equation used was based on Eq. The sample set included 12 samples each in the range of 0. These were treated in the same way as for binary mixes. Four components mixes were similar to three-component mixes with the addition of PETN.

Table 2 contains the calculated values for the sensitivity and specificity.

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Discriminating functions F1, F2, and F3 were obtained. The functions captured nearly all the statistically pertinent information of the DA, contributing to F3 was not as effective as the other two DA functions. The RDX vibrational signatures were in assigned and Eq. This model consisted of a spectrum for blue jeans cotton and a spectrum of TNT. Table 4 contains the information resulting from the study. All substrates containing TNT were predicted correctly. In spectra of samples of polyester and spandex polymer substrates the result can be explained based on the fact that these substrates have intense peaks in the same spectral range as TNT.

Spectra of cotton, polyester, and TNT were used to build another model.

This resulted in a correct classification of all samples. This further confirms the hypothesis in order to have a good prediction ability for CLS models developed it is important to include the spectra of all components, including spectra of neat substrates. For practical identification of HEs on fabrics in defense and security applications, the database to be built must contain the spectrum of the target HE, as well as the spectra for the substrate and the other components in the matrix.

The ability of the MIR laser spectroscopy assisted by CLS for detection of 1, 2, and 3 HEs in solid mixes deposited on non-reflective surfaces, such as cotton, polyester and spandex fabrics, was demonstrated. It is designed to measure absorption and polarization rotation induced by any of the two laser beams and also the visible fluorescence that results from decay of the excited states.

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  8. Two home-built diode lasers are used to produce the optical fields that later interact with room temperature rubidium atoms. Using counterpropagating beams allows velocity selection of the groups of atoms that interact with both laser beams. Blue fluorescence nm that results from decay of the intermediate 6P j states is filtered and then measured with a photomultiplier tube. Absorption and fluorescence spectra provide mutually complementary information about the interaction between the rubidium atoms and the two optical fields.. High-resolution laser spectroscopy free of Doppler broadening has made substantial progress through the study of the interaction between two optical fields and an atomic medium, such as an alkali metal vapor.

    The combination of precisely controlled experiments and the development of theoretical models is a key factor in the advance of high-resolution laser spectroscopy. The agreement between experiment and theory is quite satisfactory under many experimental circumstances Harris et al. For the purposes of this article, one can broadly classify the experiments that use atomic transitions induced by two photons in two groups. There are changes in both absorption and polarization of a probe light beam as it passes through an atomic medium interacting with optical fields.

    In the second group of experiments, the light produces excited states in the atoms that can be detected, for instance, by looking at the atomic fluorescence. In these experiments one measures the atomic population in the excited states. This paper is structured as follows. In Section 3 we present the experimental setup. Details about the construction of our diode lasers and the fluorescence detection system are also given.

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    Examples of experimental spectra obtained with this setup are shown in Section 4. Finally, conclusions are presented in Section To understand the different spectroscopy experiments that are performed in our setup we present an energy level diagram of atomic rubidium in Figure 1. The values of the total angular momenta F and hyperfine structure splittings shown here pertain to 85 Rb, and a similar diagram can be obtained for 87 Rb.

    After this two-step excitation the atoms in the 5 D j state decay back to the ground state. Detection of the excitation process can be made by measuring changes in the absorption or rotation of the linear polarization of one of the laser beams Flores-Mijangos et al. Therefore, the total angular momentum F of the initial step in our excitation ladder is well defined. If the frequency of one of the two lasers is fixed, then by scanning the frequency of the second laser one can perform velocity selective Flores-Mijangos et al.

    In our system we use balanced detection to measure the absorption and polarization of the nm beam used in the first step of the excitation.