INVESTIGATIONS ON NANOSECOND LASER-PRODUCED PLASMA IN AIR FROM THE MULTICOMPONENT MATERIAL YBA2CU3O7

The laser produced plasma from the multi-component target YBa2Cu3O7 wa s analyzed using Michelson interferometry and time resolved emission s pectroscopy. The interaction of 10 ns pulses of 1.06 mu m radiation fr om a Q-switched Nd:YAG laser at laser power densities ranging from 0.5 5 GW cm(-2) to 1.5 GW cm(-2) has been studied. Time resolved spectral measurements of the plasma evolution show distinct features at differe nt 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 ne utral and ionic species. Line averaged electron densities were deduced from interferometric line intensity measurements at various laser pow er densities. Plasma electron densities are of the order of 10(17) cm( -3) and the plasma temperature at the core region is about 1 eV. The m easurement of plasma emission line intensities of various ions inside the plasma gave evidence of multiphoton ionization of the elements con stituting the target at low laser power densities. At higher laser pow er densities the ionization mechanism is collision dominated. For elem ents such as nitrogen present outside the target, ionization is due to collisions only. (C) 1997 Elsevier Science B.V.