Anodically etched porous silicon samples have been irradiated with 85 MeV Ni ions. The ion irradiation results in a complete suppression of the major photoluminescence peak at 697 nm and the shoulder peak at 6.7 nm. In the ion-irradiated sample, the weak Pl peak, appears at 588 nm. Elastic recoil detection analysis has been used to study the changes in the hydrogen concentration profiles during ion irradiation. Infrared spectroscopy has been employed to investigate the effect of ion irradiation on the chemical species present in the porous silicon. The changes in the photoluminescence spectra have been correlated with the resulting changes in the concentration of hydrogen and chemical complexes containing Si, H and O in the porous silicon sample on irradiation.