We report on the plume dynamics of pulsed laser ablated aluminum in ambient nitrogen pressure varying from 0.01 to 70 Torr using ICCD images of the expanding plasma plume. At pressures of 0.01 to 1 Torr plasma expansion followed shock model whereas at 10 and 70 Torr plasma expansion followed drag model. The difference in the values of vapor and shock temperatures calculated at 0.1 and 70 Torr has been used to understand the formation of AlN in vapor phase. At pressures >= 1 Torr and later times plasma-gas interface showed instability in the leading edge of the expanding plume attributed to Rayleigh-Taylor instability. (c) 2004 Elsevier B.V. All rights reserved.