  The directional detection of low-energy recoil ions can provide strong
possibility for observation of dark matter in the Galaxy. Quenching factors for
5-200 keV recoil ions in N2, CO2, CF4 and CS2 gases are evaluated and
Bragg-like curves, the electronic energy deposition as a function of the
projected range, are presented. The Bragg-like curves are intended for
directional search for the dark matter candidate, WIMPs, using the gas TPC.
Quenching factors for very heavy ions produced in alpha-decay in dry air, N2,
CO2, CF4 and CS2 are also estimated and compared with experimental values.
