Diamond windows prepared using hot filament chemical vapor deposition (CVD) were irradiated with Au and Ag ions of energy 100 and 130 MeV, respectively with fluence in the range 10(10) to 3 x 10(13) ions/cm(2). Scanning electron microscopy (SEM) images showed substantial damage at the surface of the windows irradiated with Au+ of energy 100 MeV and fluence of 3 x 10(13) ions/cm(2). At some locations on the diamond windows deposited at 16 kPa, the surface layer appeared to have melted and flowed like a liquid exposing small crystallites underneath. Raman spectra of windows after irradiation showed i) a decrease in the intensity of the one-phonon line at 1332 cm(-1) along with an increase in its half width; ii) substantial reduction in the intensity of the graphite G band; and, iii) the appearance of a new band at 667 cm(-1). The band at 667 cm(-1) did not have a corresponding Stokes line and was therefore identified as a photoluminescence (PL) band. The ion induced damage and localized melting of CVD diamond windows are discussed in terms of the thermal spike model. (c) 2005 Elsevier B.V. All rights reserved.