Raman spectroscopy and molecular dynamics (MD) simulations are used to identify the vibrational spectrum of simple point defects in diamond. Two local mode frequencies are found in ion irradiated diamond. The first (with an energy of 185 meV) is clearly identified as arising from the vacancy defect, whereas a mode at 202 meV is demonstrated to be due to the [100] split interstitial. (C) 2004 Published by Elsevier B.V.