Deepak Varandani

A low cost laser-Raman spectrometer

A Jobin Yvon-Spex (HR640) monochromator with a notch filter (514·5 nm) and Ar+ ion laser has been used to set up a low cost laser Raman spectrometer. The selection and setup of the various optical components used in the present work has been solely carried out in our laboratory. The calibration of the monochromator was established from the studies of various standard mercury lines and the obtained data fitted with the reported data. Raman signals have been recorded for a number of samples e.g. diamond, ruby, carbon tetrachloride (CCI4), benzene (C6H6) and ethanol (C2H5OH). The obtained results are found to be in excellent agreement with the reported values for these materials in the literature.

Effect of 58Ni MeV ion irradiation on the resistivity of Bi1.7Pb0.35Sr2Ca2Cu3O10+x at low ion fluence

Abstract Heavy ion 58Ni MeV ion irradiation at room temperature of high Tc Bi1.7Pb0.35Sr2Ca2Cu3O10+x is reported. We show through in-situ resistivity measurements that at low fluence, formation of stable Frenkel pairs takes place together with possible defect annealing. The changes in Tc at low fluence is not appreciable. This is possibly a result of chemical substitution of Cu by Ni, a technique suitable to engineer new materials for potential applications.

A simple, versatile and high-precision quasi-adiabatic calorimeter for specific-heat measurement in the temperature range 77 - 300 K

We describe a simple and high-precision quasi-adiabatic Nernst-type calorimeter (<1%) that essentially is a modification of a previous calorimetric cell. Fundamental problems occur when samples with low thermal conductivity, low emissivity coefficient and/or specific heat, strongly varying with temperature, are measured. For those conditions a more elaborate and better procedure for the evaluation of the post-heating curves is given.

Characterization of a pneumatic differential pressure transfer standard

The paper describes a novel method for the characterization of a pneumatic differential transfer standard in the differential pressure range 0?Pa to 3.5?MPa up to a high line gas pressure of 7.0?MPa. In view of the advances in the field of automated data acquisition systems an effort has been made to incorporate such a system in the conventional pressure measurement, which uses relatively high accuracy piston gauges and the user-friendly digital transducer. The transfer standard used in the present work is a silicon strain gauge transducer, model PMP 4115, made by Druck, with an output voltage range of 0?V to 5?V with a readout unit/power supply DPI?282. The transducer was characterized against the secondary standard, which is a twin pressure balance, Model?5502, made by Desgranges et Huot, France, designated as NPL-8. The characterization was done through an automated data acquisition system using a model 9118HR A/D interface card made by Adlink, as well as the readout unit DPI?282. The uncertainty estimations showed up considerable differences between the two modes of data acquisition. The observed results were further used to generate a regression equation for the estimation of differential pressure at any given line pressure.

Raman studies of In0.53Ga0.47As/InP multi quantum wells

Abstract We report Raman scattering studies on two well characterized multi-quantum well samples of InGaAs/InP—one having 4 equal wells of 7.8 nm width (sample A) while the other has 4 unequal wells of widths 2.5, 3.9, 7.8 and 15 nm (sample B). Raman spectra of both these samples show two strong peaks at approximately 290 and 330 cm −1 due to bulk InGaAs and InP, respectively. Weak peaks at 245.7, 263.1, 276.8 cm −1 were observed apart from the InGaAs peak and a shoulder at 316.1 cm −1 near InP peak in sample A. Periodic Raman peaks were observed in both samples due to folded zone LA phonons. The presence of interfacial layers at the hetero-interfaces was evident from Raman lines.