| Abstract: | Experimental method for measuring photoacoustic(PA) signals generated by a pulsed laser beam in liquids is described. The pulsed PA technique is found to be a convenient and accurate method for determination of quantum yield in fluorescent dye solutions. Concentration dependence of quantum yield of rhodamine 6G in water is studied using the above method. The results indicate that the quantum yield decreases with increase in concentration in the quenching region in agreement with the existing reports based on radiometric measurements. |
| URI: | http://dyuthi.cusat.ac.in/purl/2499 |
| Files | Size |
|---|---|
| Dyuthi-P0290.pdf | (511.1Kb) |
| Abstract: | A method of preparation of strontium sulphide phosphors doped with europium is given. Nitrogen laser excited fluorescence emission spectra of these phosphors in the visible region are recorded. A band with line structure in the region 350-430 nm and a new broad band at 460 nm are observed. The splitting pattern for the 6p levels of Eu 2+ are given. |
| URI: | http://dyuthi.cusat.ac.in/purl/2591 |
| Files | Size |
|---|---|
| Dyuthi-P0151.pdf | (253.2Kb) |
| Abstract: | A high power Nz laser of the double-Blumlein type having a modified gas flow system, electrode configuration, and discharge geometry with minimum inductance is described. By incorporating a triggere’d-pressurized spark gap switch, arc-free operation was achieved for a wide E/P range. The device gives a peak power in excess of 700 kW with a FWHM of 3 ns and an efficiency of 0.51%, which is remarkably high for a pulsed nitrogen laser system. The dependence of output power on parameters such as operating pressure, voltage, and repetition rate are discussed. |
| URI: | http://dyuthi.cusat.ac.in/purl/2430 |
| Files | Size |
|---|---|
| Dyuthi-P0295.pdf | (1.111Mb) |
| Abstract: | High resolution optogalvanic spectrum of the (11, 7) band in the first positive system of nitrogen molecule has been recorded from 17179 to 17376 cm- 1. Assignment of 432 rotational lines belonging to the 27 branches of this band has been carried out. |
| URI: | http://dyuthi.cusat.ac.in/purl/2446 |
| Files | Size |
|---|---|
| Dyuthi-P0307.pdf | (304.6Kb) |
| Abstract: | Doppler limited high resolution spectrum in the wavelength region 17224 to 17236 cm−1 of the first positive system (B 3Π g −A 3Σ u + ) of the N2 molecule is recorded by optogalvanic spectroscopic technique using a single mode ring dye laser. It is observed that the intensity and line width of the rotational line increase with the discharge current. Dependence of the collision broadening coefficient on the current was also evaluated. |
| URI: | http://dyuthi.cusat.ac.in/purl/2637 |
| Files | Size |
|---|---|
| Dyuthi-P0196.pdf | (533.5Kb) |
| Abstract: | Artificial neural networks (ANNs) are relatively new computational tools that have found extensive utilization in solving many complex real-world problems. This paper describes how an ANN can be used to identify the spectral lines of elements. The spectral lines of Cadmium (Cd), Calcium (Ca), Iron (Fe), Lithium (Li), Mercury (Hg), Potassium (K) and Strontium (Sr) in the visible range are chosen for the investigation. One of the unique features of this technique is that it uses the whole spectrum in the visible range instead of individual spectral lines. The spectrum of a sample taken with a spectrometer contains both original peaks and spurious peaks. It is a tedious task to identify these peaks to determine the elements present in the sample. ANNs capability of retrieving original data from noisy spectrum is also explored in this paper. The importance of the need of sufficient data for training ANNs to get accurate results is also emphasized. Two networks are examined: one trained in all spectral lines and other with the persistent lines only. The network trained in all spectral lines is found to be superior in analyzing the spectrum even in a noisy environment. |
| URI: | http://dyuthi.cusat.ac.in/purl/2617 |
| Files | Size |
|---|---|
| Dyuthi-P0178.pdf | (693.9Kb) |
| Abstract: | A comparat ive study of the effect oflaser in inducing chro mosomal aberrat ions at 4gg nm was done in View j aba L. (faba bean) and Allium ccpa L. (onion) with Argon ion laser (Spectra Physics Model 171). Seeds and bulbs of V.jaba and A. eepa were subjected to laser irra diation by 4gg nm excitations from Argon ion laser source at power levels 200 and 400 mW with power densities 2.25 mW em" and 4.49 mW em" and ditTerent exposure times (10, 20, 30 & 40 minutes). Similar to the effect of oth er physical and chemical mutagens, laser caused a dose dependent decrease in mitotic index and a rise in mitotic aberrations when compared to the control. In both plant species, mutations were observed in all stages of mitotic cell cycle. The total percentage of aberrations was two fold higher at 400 mW than at 200 mW exposure. |
| Description: | GENETICS and BREEDING Volume 28 Number3-4 pp. 27-33, 1996/1997 |
| URI: | http://dyuthi.cusat.ac.in/purl/4728 |
| Files | Size |
|---|---|
| Induction of mi ... L. and Allium cepa L..pdf | (3.037Mb) |
| Abstract: | Laser irradiation at wavelength 514 nm was used to study the effect, of lasers in inducing chromosomal aberrations at mitosis. This study offers a new radiation system which could be used for the induction of mutations. Results are compared with those obtained from studies using y-rays as irradiation source. |
| URI: | http://dyuthi.cusat.ac.in/purl/2463 |
| Files | Size |
|---|---|
| Dyuthi-CPG75.pdf | (10.32Mb) |
| Abstract: | The effect of ambient gas on the dynamics of the plasma generated by laser ablation of a carbon target using 1.06 μm radiation from a Q-switched Nd:YAG laser has been investigated using a spectroscopic technique. The emission characteristics of the carbon plasma produced in argon, helium and air atmospheres are found to depend strongly on the nature and pressure of the surrounding gas. It has been observed that hotter and denser plasmas are formed in an argon atmosphere rather than in helium or air as an ambient. |
| URI: | http://dyuthi.cusat.ac.in/purl/2388 |
| Files | Size |
|---|---|
| Dyuthi-P0207.pdf | (678.2Kb) |
| Abstract: | It is shown that the invariant integral, viz., the Kolmogorov second entropy, is eminently suited to characterize EEG quantitatively. The estimation obtained for a "clinically normal" brain is compared with a previous result obtained from the EEG of a person under epileptic seizure. |
| URI: | http://dyuthi.cusat.ac.in/purl/2636 |
| Files | Size |
|---|---|
| Dyuthi-P0195.pdf | (355.6Kb) |
| Abstract: | Thermal lensing effect was studied in aqueous solutions of rhodamine B using 532 nm, 9 ns pulses from a Nd:YAG laser. A low intensity He-Ne laser beam was used for probing the thermal lens. Results obtained show that it is appropriate to use this technique for studying nonlinear absorption processes like two photon absorption or excited state absorption and for analyzing dimerization equilibria. |
| URI: | http://dyuthi.cusat.ac.in/purl/2396 |
| Files | Size |
|---|---|
| Dyuthi-P0212.pdf | (963.8Kb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1692 |
| Files | Size |
|---|---|
| Dyuthi-T0171.pdf | (3.523Mb) |
| Abstract: | The laser produced plasma from the multi-component target YBa2CU3O7 was analyzed using Michelson interferometry and time resolved emission spectroscopy. The interaction of 10 ns pulses of 1.06 mum radiation from a Q-switched Nd:YAG laser at laser power densities ranging from 0.55 GW cm-2 to 1.5 GW cm-2 has been studied. Time resolved spectral measurements of the plasma evolution show distinct features at different points in its temporal history. For a time duration of less than 55 ns after the laser pulse (for a typical laser power density of 0.8 GW cm-2, the emission spectrum is dominated by black-body radiation. During cooling after 55 ns the spectral emission consists mainly of neutral and ionic species. Line averaged electron densities were deduced from interferometric line intensity measurements at various laser power densities. Plasma electron densities are of the order of 1017 cm-3 and the plasma temperature at the core region is about 1 eV. The measurement of plasma emission line intensities of various ions inside the plasma gave evidence of multiphoton ionization of the elements constituting the target at low laser power densities. At higher laser power densities the ionization mechanism is collision dominated. For elements such as nitrogen present outside the target, ionization is due to collisions only. |
| URI: | http://dyuthi.cusat.ac.in/purl/2459 |
| Files | Size |
|---|---|
| Dyuthi-P0320.pdf | (672.0Kb) |
| Abstract: | The growth kinetics of an aerial bacterial colony on solid agar media was studied using laser induced fluorescence technique. Fluorescence quenching of Rhodamin B by the bacterial colony was utilized for the study. The lag phase, log phase, and stationary phase of growth curve of bacterial colony was identified by measuring peak fluorescence intensity of dye doped bacterial colony. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2045 |
| Files | Size |
|---|---|
| Kinetics of bacterial colony...pdf | (180.7Kb) |
| Abstract: | We present a compact solid-state laser based on leaky mode propagation from a dye-doped polymer free-standing film waveguide. The edge emitted spectrum clearly indicated the existence of periodic resonant modes. The reflections from the lateral faces of the free-standing film provided the optical feedback thus giving rise to a Fabry–Perot like optical cavity. This together with the guidance through the gain medium gave rise to intense narrow emission lines. For a pump energy of 1.82 mJ/pulse, an intense line with FWHM ∼0.4 nmwas observed at 576.5 nm. |
| URI: | http://dyuthi.cusat.ac.in/purl/1783 |
| Files | Size |
|---|---|
| Laser emission from transversely.pdf | (247.6Kb) |
| Abstract: | We present a compact solid-state laser based on leaky mode propagation from a dye-doped polymer free-standing film waveguide. The edge emitted spectrum clearly indicated the existence of periodic resonant modes. The reflections from the lateral faces of the free-standing film provided the optical feedback thus giving rise to a Fabry–Perot like optical cavity. This together with the guidance through the gain medium gave rise to intense narrow emission lines. For a pump energy of 1.82 mJ/pulse, an intense line with FWHM ∼0.4 nmwas observed at 576.5 nm. |
| URI: | http://dyuthi.cusat.ac.in/purl/1782 |
| Files | Size |
|---|---|
| Dyuthi-P0259.pdf | (247.6Kb) |
| Abstract: | We present a compact solid-state laser based on leaky mode propagation from a dye-doped polymer free-standing film waveguide. The edge emitted spectrum clearly indicated the existence of periodic resonant modes. The reflections from the lateral faces of the free-standing film provided the optical feedback thus giving rise to a Fabry–Perot like optical cavity. This together with the guidance through the gain medium gave rise to intense narrow emission lines. For a pump energy of 1.82 mJ/pulse, an intense line with FWHM ∼0.4 nmwas observed at 576.5 nm. |
| URI: | http://dyuthi.cusat.ac.in/purl/1784 |
| Files | Size |
|---|---|
| Laser emission from transversely.pdf | (247.6Kb) |
| Abstract: | We demonstrate the possibility of realizing, all-optical switching in gold nanosol. Two overlapping laser beams are used for this purpose, due to which a low-power beam passing collinear to a high-power beam will undergo cross phase modulation and thereby distort the spatial profile. This is taken to advantage for performing logic operations. We have also measured the threshold pump power to obtain a NOT gate and the minimum response time of the device. Contrary to the general notion that the response time of thermal effects used in this application is of the order of milliseconds, we prove that short pump pulses can result in fast switching. Different combinations of beam splitters and combiners will lead to the formation of other logic functions too. |
| URI: | http://dyuthi.cusat.ac.in/purl/2607 |
| Files | Size |
|---|---|
| Dyuthi-P0167.pdf | (970.9Kb) |
| Abstract: | Optical fiber based laser induced fluorescence (LIF) measurements were carried out using Rhodamine B to analyze two different species of bacteria , a Gram-positive bacteria namely Bacillus .cmithii , and fibrin alginolvticus, a Gram-' negative bacteria . The fiber sensor was clearly able to distinguish between the two species of bacteria . Quenching effect of the dye Rhodamine B by Bacillus smitltii was observed . The effect of dye on the samples was also studied in detail. |
| URI: | http://dyuthi.cusat.ac.in/purl/908 |
| Files | Size |
|---|---|
| Sandeep,P M and ... r induced...,march2007.PDF | (3.835Mb) |
| Abstract: | Fluorescence of BaS: Sm phosphor has been studied using a pulsed Nitrogen laser (337.1 nm) as the excitation source. The spectrum consists of a broad band in the region 540–660nm superposed by the characteristic Sm3+ lines. Energy level splitting pattern of Sm3+ due to crystal field effects has been calculated and relevent field parameters are evaluated. Analysis shows that Sm3+ takes up Ba2+ substitutional sites. |
| URI: | http://dyuthi.cusat.ac.in/purl/2641 |
| Files | Size |
|---|---|
| Dyuthi-P0328.pdf | (216.9Kb) |
Dyuthi Digital Repository Copyright © 2007-2011 Cochin University of Science and Technology. Items in Dyuthi are protected by copyright, with all rights reserved, unless otherwise indicated.