Now showing items 21-25 of 25
| Abstract: | Thermal diffusivity measurements are carried out in certain organic liquids using the pulsed dual beam thermal lens technique. The 532 nm pulses from a frequency doubled Q-switched Nd:YAG laser are used as the heating source and an intensity stabilized He-Ne laser serves as the probe beam. Experimental determination of the characteristic time constant of the transient thermal lens signal is verified theoretically. Measured thermal diffusivity values are in excellent agreement with literature values. |
| URI: | http://dyuthi.cusat.ac.in/purl/2390 |
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| Dyuthi-P0199.pdf | (133.9Kb) |
| Abstract: | The effect of pH on the fluorescence efficiency of fluorescein is evaluated using thermal lens technique. Fluorescence efficiency increases as the sample becomes more and more alkaline. But when fluorescein is mixed with rhodamine B fluorescence quenching of fluorescein takes place with the excitation of rhodamine B. The electronic energy transfer in this mixture is investigated using Optical Parametric Oscillator as the excitation source. The effect of pH on the efficiency of energy transfer in fluorescein–rhodamine B mixture is presented. |
| URI: | http://dyuthi.cusat.ac.in/purl/2418 |
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| Dyuthi-P0265.pdf | (334.2Kb) |
| Abstract: | Laser radiation at 1.06 µm from a pulsed Nd:YAG laser was focused onto a multielement YBa2Cu3O7 target in vacuum and the plasma thus generated was studied using time-resolved spectroscopic techniques. Line broadening of the Ba I emission line at 553.5 nm was monitored as a function of time elapsed after the incidence of a laser pulse on the target. Measured line profiles of barium species were used to infer the electron density and temperature, and the time evolution of these important plasma parameters has been worked out. |
| URI: | http://dyuthi.cusat.ac.in/purl/2395 |
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| Dyuthi-P0204.pdf | (216.2Kb) |
| Abstract: | We report time resolved study of C2 emission from laser produced carbon plasma in presence of ambient helium gas. The 1.06µm: radiation from a Nd:YAG laser was focused onto a graphite target where it·produced a transient plasma. We observed double peak structure in the time profile of C2 species. The twin peaks were observed only after a threshold laser fluence. It is proposed that the faster velocity component in the temporal profiles originates mainly due to recombination processes. The laser fluence and ambient gas dependence of the double peak intensity distribution is also reported. |
| URI: | http://dyuthi.cusat.ac.in/purl/2462 |
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| Dyuthi-P0324.pdf | (648.1Kb) |
| Abstract: | Time and space resolved studies of emission from CN molecules have been carried out in the plasma produced from graphite target by 1.06 urn pulses from a Q-switched Nd:YAG laser. Depending on the laser pulse energy, time of observation and position of the sampled volume of the plasma, the features of the emission spectrum are found to change drastically. The vibrational temperature and population distribution in the different vibrational levels have been studied as functions of distance, time, laser energy and ambient gas pressure. Evidence for nonlinear effects of the plasma medium such as self focusing which exhibits threshold-like behaviour are also obtained. Temperature and electron density of the plasma have been evaluated using the relative line intensities of successive ionization stages of carbon atom. These electron density measurements are verified by using Stark broadening method. |
| URI: | http://dyuthi.cusat.ac.in/purl/2456 |
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| Dyuthi-P0317.pdf | (1.672Mb) |
Now showing items 21-25 of 25
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