Time-of-flight spectrometers, currently used for charge state analysis of low-energy recoil ions produced in swift ion-atom collisions, are shown to provide, under specific conditions, charge state characteristic peaks whose shape directly reflects the distribution of the initial velocity component of the extracted ions along the extraction axis. Advantage is taken of this property to determine, with the help of a simple model for velocity distributions, the mean recoil energy of Ne 7+ to 9' and Ar 9' to 16' ions produced by a 27 MeVa.m.u.-' Xe 52' projectile beam.