The dynamics of an aluminum plasma plume expanding in atmosphere air was studied experimentally. The plasma was produced by irradiating a thin film aluminum with a single pulse laser beam in ambient air. The laser pulse was provided by second harmonic of a Q-switched Nd:YAG laser with ~10 nsec pulse duration and ~ 50 mJ energy per pulse. A low power CW He-Ne laser beam was also used for probing the plasma. Both transmission and reflection of the probe were monitored temporally during the ablation time scale. For transmission three temporal stages can be distinguished and there is a substantial reduction in the reflection coefficient when laser ablation occurs.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.