We have probed the interaction of intense laser fields with Xe clusters by measuring the energy and charge state distributions of emitted ions and electrons using ultrafast 20-fs pulses. This work demonstrates that the energetic particle emissions from laser-cluster interactions can be optimized by manipulating the character of ultrafast laser pulses, ie, pulse duration and sign of chirp. The mean and maximum ion energies as high as 0.1 and 2 MeV, respectively, are achieved when Xe clusters are irradiated by 500-fs pulses with negative chirp as an optimal condition under a laser peak intensity of 2× 10 17 W/c m 2. The mean ion energy obtained from 500-fs pulses with negative chirp is found to be about 1.6 times larger than that with positive chirp.