V. L. N. Sridhar Raja

Bio: V. L. N. Sridhar Raja is an academic researcher from Indian Space Research Organisation. The author has contributed to research in topics: Plasma parameters & Laser ablation. The author has an hindex of 3, co-authored 6 publications receiving 59 citations.

Molybdenum ion as a structural probe in PbO-Sb2O3-B2O3 glass system by means of dielectric and spectroscopic investigations

Abstract: PbO-Sb2O 3 -B 2 O3 glasses containing different concentrations of MoO 3 ranging from 0 to 5 mol % were prepared. A number of studies have been carried out on these glasses comprising differential thermal analysis, infrared and optical absorption, Raman and ESR spectra, magnetic susceptibility and measurements of dielectric properties (constant e', loss tan δ and a.c. conductivity σ ac . over a range of frequency and temperature) of these glasses. The results have been analyzed in terms of different oxidation states of molybdenum ions. The'analysis indicates that when the concentration of MoΟ 3 is <0.6 mol %, molybdenum ions exist mostly in the Mo 6+ state, occupy network forming positions with MoO 2- 4 structural units and increase the rigidity of the glass network. When MoO 3 is present in higher concentrations, molybdenum ions seem to exist mostly in the Mo 5+ state and occupy modifying positions.

Modeling of laser induced breakdown spectroscopy for very low-pressure conditions

Abstract: Laser Induced Breakdown Spectroscopy (LIBS) can be considered as a prominent technology for compositional analysis of materials in low-pressure space applications. In space applications, usually LIBS is conducted in a low-pressure environment and proper understanding of the plasma parameters is significant for any improvement in the system. A model is developed to describe the heating and subsequent melting, vaporization and ionization of a target material during LIBS process. A numerical model based on one-dimensional thermal conductivity equation is being used to simulate the target evaporation and a hydrodynamic model is used to simulate plume expansion. Further, an experimental approach of measuring spectral emission from the ablation plume using emission spectroscopy and estimating the plasma state, such as the ionization species, and average plasma temperature, is investigated. An important result of this work is that for different ambient conditions, laser ablation plume dynamics can be estimated.

Realization and Design Aspects of Mini Laser Raman Spectroscope Electronics for Planetary Surface Exploration

Abstract: Mini Laser Raman Spectroscope (MLRS) is currently under development at LEOS-ISRO, which will be part of rover in the follow up missions to Moon and Mars. Amidst the variety of instruments that were flown or are to be flown in space missions, the instruments based on Raman Spectroscopy are one of the best-suited tools for analyzing minerals on planetary surfaces. This paper primarily focuses on the design requirements for realizing MLRS electronics. It discusses the wavelength stabilization aspects of the laser diode source (785 nm) and the CCD readout electronics designed to capture the relatively weak scattered Raman radiations. Also the paper sheds light on the realization aspects of the data acquisition system that will be used to characterize and verify the functionality of the instrument.

Laser-induced breakdown spectroscopy.

Abstract: ■ CONTENTS General Information: Books, Reviews, and Conferences 640 Fundamentals 641 Interaction of Laser Beam with Matter 641 Factors Affecting Laser Ablation and LaserInduced Plasma Formation 642 Influence of Target on the Laser-Induced Plasmas 642 Influence of Laser Parameters on the LaserInduced Plasmas 643 Laser Wavelength (λ) 643 Laser Pulse Duration (τ) 643 Laser Pulse Energy (E) 645 Influence of Ambient Gas on the Laser-Induced Plasmas 645 LIBS Methods 647 Double Pulse LIBS 647 Femtosecond LIBS 651 Resonant LIBS 652 Ranging Approaches 652 Applications 654 Surface Inspection, Depth Profiling, and LIBS Imaging 654 Cultural Heritage 654 Industrial Analysis 655 Environmental Monitoring 656 Biomedical and Pharmaceutical Analysis 658 Security and Forensics 659 Analysis of Liquids and Submerged Solids 660 Space Exploration and Isotopic Analysis 662 Space Exploration 662 Isotopic Analysis 662 Conclusions and Future Outlook 663 Author Information 664 Corresponding Author 664 Notes 664 Biographies 664 Acknowledgments 664 References 664

Structural investigations on PbO-Sb(2)O(3)-B(2)O(3):CoO glass ceramics by means of spectroscopic and dielectric studies.

Abstract: PbO–Sb2O3–B2O3 glasses mixed with different concentrations of CoO (ranging from 0 to 2.0 mol%) were crystallized. The samples were characterized by x-ray diffraction, scanning electron microscopy and differential scanning calorimetric techniques. The x-ray diffraction and scanning electron microscopic studies have revealed the presence of CoSb2O6, Co2.33Sb0.67O4, Pb5Sb2O8,Pb3(SbO4)2, PbB4O7 and Co3O4 crystalline phases in these samples. The DSC studies have indicated the spreading of the crystallization from the inside to the surface of the samples as the concentration of the crystallizing agent is increased. The IR and Raman spectroscopic studies have pointed out the existence of conventional BO3, BO4, SbO4 and also CoIII–O structural units in the glass ceramic samples. These studies have further indicated the decreasing concentration of symmetrical structural vibrational groups with increase in the concentration of CoO. The results of various studies, namely dielectric properties over a range of frequency and temperature, photo-induced birefringence, optical absorption, fluorescence and magnetic susceptibility at room temperature of PbO–Sb2O3–B2O3:CoO glass ceramics, have also been reported. The variations observed as a function of the concentration of crystallizing agent in all these properties have been analyzed in the light of different oxidation states and environments of cobalt ions in the glass ceramic network.