TIME-RESOLVED STUDY OF CN BAND EMISSION FROM PLASMA GENERATED BY LASER IRRADIATION OF GRAPHITE

Time and space resolved studies of emission from CN molecules have bee n carried out in the plasma produced from graphite target by 1.06 mu m pulses from a Q-switched Nd:YAG laser. Depending on the laser pulse e nergy, time of observation and position of the sampled volume of the p lasma, the features of the emission spectrum are found to change drast ically. The vibrational temperature and population distribution in the different vibrational levels have been studied as functions of distan ce, time, laser energy and ambient gas pressure. Evidence for nonlinea r effects of the plasma medium such as self focusing which exhibits th reshold-like behaviour are also obtained. Temperature and electron den sity of the plasma have been evaluated using the relative line intensi ties of successive ionization stages of carbon atom. These electron de nsity measurements are verified by using Stark broadening method. (C) 1997 Elsevier Science B.V.