Browsing by Author "Jagdish P. Singh"

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Chemical constituents of artabotrys odoratissimus (SEEDS)
(2009) Jagdish P. Singh; Alok K. Singh; Archana Singh; Rakesh Ranjan
3-Hydroxy-9-methoxypterocarpan, nonacosanoic acid 2', 3'-dihydroxypropyl ester, pentacosanoic acid 2,-3'-dihydroxypropyl ester and docosanoic acid have been isolated for the first time from the seeds of Artabotrys odoratissimus and identified by spectroscopic data of these natural products and their derivatives.
Fundamentals of LIBS and recent developments
(Elsevier, 2020) Surya N. Thakur; Jagdish P. Singh
When a pulsed laser beam of high intensity is focused on a target, it generates plasma from the material. In recent years there has been much interest both in an increased understanding of laser-induced plasmas (LIPs) and in the development of their applications. Laser-induced breakdown spectroscopy (LIBS) is used for elemental analysis of targets from which the luminous plasma is generated and it can also be applied to determine the temperature, electron density, and atom density in the LIP. Reliable elemental analysis needs knowledge of laser wavelength, its irradiance, the amount of ablated and vaporized sample, and the ability of the resulting plasma to absorb the optical energy. During the last decade, some very significant progress has been made in the three basic components of LIBS, namely instrumentation, mechanism of LIP, and spectral data processing algorithms. A classic example of these developments is represented by the use of LIBS equipment on board the Curiosity rover exploring the surface of Mars. This chapter briefly describes the basic components and the underlying physical processes that are essential to appreciate the range of applications and power of LIBS. © 2020 Elsevier B.V. All rights reserved.
Laser-Induced Breakdown Spectroscopy
(Elsevier, 2007) Jagdish P. Singh; Surya N. Thakur
Laser induced breakdown spectroscopy (LIBS) is basically an emission spectroscopy technique where atoms and ions are primarily formed in their excited states as a result of interaction between a tightly focused laser beam and the material sample. The interaction between matter and high-density photons generates a plasma plume, which evolves with time and may eventually acquire thermodynamic equilibrium. One of the important features of this technique is that it does not require any sample preparation, unlike conventional spectroscopic analytical techniques. Samples in the form of solids, liquids, gels, gases, plasmas and biological materials (like teeth, leaf or blood) can be studied with almost equal ease. LIBS has rapidly developed into a major analytical technology with the capability of detecting all chemical elements in a sample, of real- time response, and of close-contact or stand-off analysis of targets. The present book has been written by active specialists in this field, it includes the basic principles, the latest developments in instrumentation and the applications of LIBS . It will be useful to analytical chemists and spectroscopists as an important source of information and also to graduate students and researchers engaged in the fields of combustion, environmental science, and planetary and space exploration. © 2007 Elsevier B.V. All rights reserved.
Laser-Induced Breakdown Spectroscopy, Second Edition
(Elsevier, 2020) Jagdish P. Singh; Surya N. Thakur
Laser-Induced Breakdown Spectroscopy, Second Edition, covers the basic principles and latest developments in instrumentation and applications of Laser Induced Breakdown Spectroscopy (LIBS). Written by active experts in the field, it serves as a useful resource for analytical chemists and spectroscopists, as well as graduate students and researchers engaged in the fields of combustion, environmental science, and planetary and space exploration. This fully revised second edition includes several new chapters on new LIBS techniques as well as several new applications, including flame and off-gas measurement, pharmaceutical samples, defense applications, carbon sequestration and site monitoring, handheld instruments, and more. LIBS has rapidly developed into a major analytical technology with the capability of detecting all chemical elements in a sample, of real- time response, and of close-contact or stand-off analysis of targets. It does not require any sample preparation, unlike conventional spectroscopic analytical techniques. Samples in the form of solids, liquids, gels, gases, plasmas, and biological materials (like teeth, leaves, or blood) can be studied with almost equal ease. This comprehensive reference introduces the topic to readers in a simple, direct, and accessible manner for easy comprehension and maximum utility. © 2020 Elsevier B.V. All rights reserved.
Photoacoustic and Photothermal Spectroscopy: Principles and Applications
(Elsevier, 2022) Surya N. Thakur; Virendra N. Rai; Jagdish P. Singh
Photoacoustic and Photothermal Spectroscopy: Principles and Applications introduces the basic principles, instrumentation and major developments in the many applications of Photoacoustic and Photothermal Spectroscopy over the last three decades. The book explains the processes of sound generation by periodic optical excitation and ultrasonic generation by pulsed laser excitation and describes the workings of photoacoustic cells equipped with microphones and piezoelectric transducers. Photoacoustic imaging (PAI) is one of the fastest-growing imaging modalities of recent times. It combines the advantages of ultrasound and optical imaging techniques. These non-invasive and non-destructive techniques offer many benefits to users by enabling spectroscopy of opaque and inhomogeneous materials, (solid, liquid, powder, gel, gases) without any sample preparation, and more. © 2023 Elsevier Inc. All rights reserved.
Photoacoustic spectroscopy of atmospheric pollutants and biomarker gases
(Elsevier, 2022) Surya N. Thakur; Jagdish P. Singh; Gaurangdhar Baruah
In this chapter, we have discussed in detail the design and construction of photoacoustic cells, both with static and flowing gas samples, employing a microphone or a quartz tuning fork for the PA signal generation. Examples of each type of detection system contain their use in practical measurements for trace detection of polluting and harmful molecules. One of the important applications of PA spectroscopy is the measurement of aerosols, since this technique is insensitive to light scattering. Diode laser-based aerosol measuring instruments have been tested in field measurements, and results have been found to be in good agreement with those of other conventional techniques. Atmospheric air contains a mixture of different aerosols originating from different sources, such as diesel engine exhaust, natural mineral dust, and wood burning. It is possible to discriminate aerosols by PA measurements at a number of different wavelengths. H2S is a key chemical mediator that exerts a vital role in diverse physiological and pathological processes, but in vivo tracking of endogenous H2S generation is very difficult. Recently, a nanocomposite probe has made it possible to detect endogenous H2S generation by PA spectroscopy in a tumor-bearing mouse model. © 2023 Elsevier Inc. All rights reserved.
Photoacoustic studies on excitation transfer in organic dyes in solutions and on surfaces
(Elsevier, 2022) Virendra N. Rai; Jagdish P. Singh; Surya N. Thakur
Study of excitation transfer in organic dyes is important for enhancing the efficiency and the bandwidth (spectral range) of the dye lasers. Both the properties of dye lasers are very useful in spectroscopic measurements. The mechanisms of excitation transfer processes are presented along with the excitation transfer in different systems. To better understand the excitation transfer processes in a dye mixture, photoacoustic spectral characteristics of Rh6G and RhB dye in a mixed solution are investigated. Photoacoustic spectroscopy of dyes adsorbed on Al2O3 surfaces provides information about the relaxation process of excited dye molecules in contact with the surfaces. An enhancement in the photoacoustic signal is observed for dye mixtures between 480 and 530nm. Spectral bandwidth of the mixture of dyes is enlarged as compared with that of the individual dyes. This has been explained in terms of the dominance of the resonance excitation transfer from Rh6G to RhB in comparison with the collisional transfer process. The spectra of mixtures also exhibit a blueshift due to dimmer formation in Rh6G. The spectra of dyes adsorbed on Al2O3 surfaces show a redshift due to photobleaching. The photoacoustic signal also increases for the entire spectral range of RhB dye solution after bubbling O2 gas. This has been explained as due to the increased intersystem crossing rate in the solution after bubbling the O2 gas. © 2023 Elsevier Inc. All rights reserved.
Physics and techniques of photoacoustic spectroscopy of liquids
(Elsevier, 2022) Surya N. Thakur; Virendra N. Rai; Jagdish P. Singh
Photoacoustic spectroscopy (PAS) of liquid samples is challenging with applications in diverse fields of research and analysis. The study of photoacoustic (PA) signal generation in the liquid sample has been presented along with the experimental setups having appropriate design of sample cuvette and the detection device. PA techniques useful in measuring the optical as well as the thermal properties of liquid samples are described. PAS allows the monitoring of dye concentration over a wide concentration range without any dilution or other sample preparations. The use of a flow cell makes the PA measurements possible in a continuous fashion, where the signal is not affected by the flow velocity. The development of an open-cell PA spectrometer for liquid samples is also discussed for remote sensing, which demonstrates the viability of the pulsed indirect photoacoustic spectroscopy method for detection and identification of liquids at ranges up to several tens of meters. Some of the recent advances in PAS of liquid include the measurement of flow speed and the liquid viscosity. These measurements are important in medical diagnostics and research. PA technique can be an efficient and convenient method for measurement and daily monitoring of blood viscosity with only a small amount of sample. These results indicate a bright future prospect for PAS of liquid samples. © 2023 Elsevier Inc. All rights reserved.
Preface
(Elsevier, 2022) Surya N. Thakur; Virendra N. Rai; Jagdish P. Singh
[No abstract available]
Preface
(Elsevier, 2020) Jagdish P. Singh; Surya N. Thakur
[No abstract available]
Quantitative analysis of gallstones using laser-induced breakdown spectroscopy
(OSA - The Optical Society, 2008) Vivek K. Singh; Vinita Singh; Awadhesh K. Rai; Surya N. Thakur; Pradeep K. Rai; Jagdish P. Singh
The utility of laser-induced breakdown spectroscopy (LIBS) for categorizing different types of gallbladder stone has been demonstrated by analyzing their major and minor constituents. LIBS spectra of three types of gallstone have been recorded in the 200-900 nm spectral region. Calcium is found to be the major element in all types of gallbladder stone. The spectrophotometric method has been used to classify the stones. A calibration-free LIBS method has been used for the quantitative analysis of metal elements, and the results have been compared with those obtained from inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements. The single-shot LIBS spectra from different points on the cross section (in steps of 0.5 mm from one end to the other) of gallstones have also been recorded to study the variation of constituents from the center to the surface. The presence of different metal elements and their possible role in gallstone formation is discussed. © 2008 Optical Society of America.
Three new cyclopeptide alkaloids from Zizyphus species
(2008) Manoj B. Pandey; Ashok K. Singh; Jagdish P. Singh; Virendra P. Singh; Vidya B. Pandey
Two new cyclopeptide alkaloids, xylopyrine-D and xylopyrine-E, from Zizyphus xylopyra and a new alkaloid, jubanine-E, from Zizyphus jujuba have been isolated and their structures were established by chemical and spectral evidences. © 2008 Taylor & Francis.
Two-coherent-wave coupling in Rhodamine 110-doped boric acid glass solid films
(Optical Society of American (OSA), 2007) Ramesh C. Sharma; Anjan Barman; Surya N. Thakur; Jagdish P. Singh
We report the energy-transfer efficiency in a saturable absorber nonlinear media by two-coherent-wave coupling using the Doppler shift. Intensity-dependent nondegenerate two-beam coupling has been studied in Rhodamine 110-doped boric acid glass films. Two beams have been described in the limit of a weak probe and a relatively strong pump at the wavelength 488 nm from a continuous-wave Ar+ laser. The results have been interpreted in terms of the four-level description of a saturable absorber. We obtained good agreement between the experimental and the theoretical results. Estimated values of the nonlinear parameters such as the saturation intensity, refractive index, and the response time of the optical nonlinearity have been obtained at different pump beam intensities for the first time, to our knowledge, in the Rhodamine 110-doped film. © 2007 Optical Society of America.
Vibrationally selective radiative and non-radiative transitions in gaseous hydrogen molecules
(2011) Ramesh C. Sharma; Thomas A. Waigh; Anil K. Maini; Surya N. Thakur; Jagdish P. Singh; King C. Lin
An efficient vibrationally selective technique to build-up the v″ = 1 vibrational levels in gaseous hydrogen is demonstrated using stimulated Raman pumping (SRP). Both photo-acoustic Raman spectroscopy (PARS) and coherent anti-Stokes Raman spectroscopy (CARS) are used to study non-radiative and radiative (v″ = 0 and v″ = 1) transitions in gaseous H2 molecules. The population fraction in the v″ = 1 vibrational level has been estimated using combined photo-acoustic and coherent anti-Stokes Raman spectroscopy with stimulated Raman pumping. © 2011 Elsevier B.V. All rights reserved.
Xylopyrine-F, a new cyclopeptide alkaloid from Zizyphus xylopyra
(2008) Manoj B. Pandey; Jagdish P. Singh; Ashok K. Singh; Virendra P. Singh
A new 14-membered ring cyclopeptide alkaloid xylopyrine-F, together with known alkaloids nummularine-P and sativanine-H, has been isolated from the root bark of Zizyphus xylopyra and their structures were established by chemical and spectral evidences. © 2008 Taylor & Francis.