Dynamics of laser produced silver plasma under film deposition conditions studied using optical emission spectroscopy

Laser produced plasma from silver is generated using a Q-switched Nd:YAG laser. Optical emission spectroscopy is used to carry out time of flight (TOF) analysis of atomic particles. An anomalous double peak profile in the TOF distribution is observed at low pressure. A collection of slower species emerge at reduced pressure below 4 X lO-3 mbar and this species has a greater velocity spread. At high pressure the plasma expansion follows the shockwave model with cylindrical symmetry whereas at reduced pressure it shows unsteady adiabatic expansion (UAE). During UAE the species show a parabolic increases in the expansion time with radial distance whereas during shock wave expansion the exponent is less than one. The angular distribution of the ablated species in the plume is obtained from the measurement of optical density of thin films deposited on to glass substrates kept perpendicular to the plume. There is a sharp variation in the film thickness away from the film centre due to asymmetries in the plume.

Photoemission optogalvanic studies with copper as target electrode

Photoemission optogalvanaic (POG) effect has been observed by irradiating copper target electrode, in a nitrogen discharge cell using 1.06 μm and frequency doubled 532 nm Nd:YAG laser pulse. Measurement of the nature of the variation of POG signal strength with 532 nm laser fluence confirms the two photon induced photoelectric emission from copper. However, using 1.06 μm laser pulses thermally assisted photoemission is observed.

On tuning the orientation of grains of spray pyrolysed ZnO thin films

Effect of varying spray rate on the structure and optoelectronic properties of spray pyrolysed ZnO film is analysed. ZnO films were characterised using different techniques such as X-ray diffraction (XRD), photoluminescence, electrical resistivity measurement, and optical absorption. The XRD analysis proved that, with the increase in spray rate, orientation of the grains changed from (1 0 1) plane to (0 0 2) plane. The films exhibited luminescence in two regions—one was the ‘near band-edge’ (NBE) (∼380 nm) emission and the other one was the ‘blue-green emission’ (∼503 nm). Intensity of the blue-green emission decreased after orientation of grains shifted to (0 0 2) plane. Scanning electron microscope (SEM) analysis of the films asserts that spray rate has major role in improving the crystallographic properties of the films. Moreover resistivity of the films could be lowered to 2.4×10−2 cm without any doping or post-deposition annealing

Characteristics of near surface crustal deformation associated with shield seismicity

The purpose of the present study is to understand the surface deformation associated with the Killari and Wadakkancheri earthquake and to examine if there are any evidence of occurrence of paleo-earthquakes in this region or its vicinity. The present study is an attempt to characterize active tectonic structures from two areas within penisular India: the sites of 1993 Killari (Latur) (Mb 6.3) and 1994 Wadakkancheri (M 4.3) earthquakes in the Precambrian shield. The main objectives of the study are to isolate structures related to active tectonism, constraint the style of near – surface deformation and identify previous events by interpreting the deformational features. The study indicates the existence of a NW-SE trending pre-existing fault, passing through the epicentral area of the 1993 Killari earthquake. It presents the salient features obtained during the field investigations in and around the rupture zone. Details of mapping of the scrap, trenching, and shallow drilling are discussed here. It presents the geologic and tectonic settings of the Wadakkancheri area and the local seismicity; interpretation of remote sensing data and a detailed geomorphic analysis. Quantitative geomorphic analysis around the epicenter of the Wadakkancheri earthquake indicates suitable neotectonic rejuvenation. Evaluation of remote sensing data shows distinct linear features including the presence of potentially active WNW-ESE trending fault within the Precambrian shear zone. The study concludes that the earthquakes in the shield area are mostly associated with discrete faults that are developed in association with the preexisting shear zones or structurally weak zones

Surface Active Substances in the Cochin Estuarine System

This study focuses on the fractionation and quantification of chlorophenols, the most important and potential pollutant in this category, the distribution and seasonal dynamics of MBAS, phenols and clorophenols and development of a model to describe the chemical reactivity of the estuary are utilizing the dynamics of boron. The CES is highly influenced by various anthropogenic activities like discharge of agricultural, industrial and urban wastes operation of shipyard, oil and other transporting activities, fishing, dredging etc. Seasonal values of MBAS showed high values in the surface water during monsoon compared to premonsoon and postmonsoon. In the Cochin estuary o-chlorophenol and p-chlorophenol showed low values in the surface water compared to bottom water in the northern part of the estuary and higher values in the surface water in the southern part

Preparation of high surface area TiO (anatase) by thermal hydrolysis 2 of titanyl sulphate solution

Highly crystalline, ultra fine TiO (anatase) having high surface area has been prepared by thermal hydrolysis of titanyl sulphate 2 solution and characterized using B.E.T surface area measurements, XRD and chemical analysis. The dependence of surface area on concentration of staffing solution, temperature of hydrolysis, duration of boiling and calcination temperature were also studied. As the boiling temperature, duration of boiling and calcination temperature increased, the surface area of TiO formed decreased significantly. 2 On increasing calcination temperature, the crystallite size of TiO also increased and gradually the phase transformation to rutile took 2 place. The onset and completion temperatures of rutilation were 700 and 10008C, respectively

Laser induced surface damage, thermal transport and microhardness studies on certain organic and semiorganic nonlinear optical crystals

N-alkyl-2,6-dimethyl-4(1H)-pyridinones, salts of 4-dimethylaminopyridine and 2-amino-5-nitropyridine are considered to be potential candidates for nonlinear optical (NLO) applications, in particular for the generation of blue-green laser radiation. Single crystals were grown following the slow evaporation technique at constant temperature. Single-shot laserinduced surface damage thresholds in the range 3–10 GW/cm2 were measured using a 18 ns Q-switched Nd:YAG laser. The surface morphologies of the damaged crystals were examined under an optical microscope and the nature of damage identified. The Vicker’s microhardness was determined at a load of 98.07 mN. The thermal transport properties, thermal diffusivity (α), thermal effusivity (e), thermal conductivity (K) and heat capacity (Cp), of the grown crystals were measured by an improved photopyroelectric technique at room temperature. All the results are presented and discussed.