A new method for detecting the halogen atoms, especially the Chlorine II 479.4 nm emission line, is presented using a TEA CO2 laser . Various alkali halide powders are compressed into pellets. The pellets are bombarded by a TEA CO2 laser (500 mJ, 100 ns) using the noble gases instead of air as the surrounding gas . The plasma is excited by the shock wave induced by the laser bombardment . The high temperature plasma produced in helium due to the high front speed is the main source for exciting the halogen ionic lines. It is proved that helium at low pressure (around 5 Torr) provides the best conditions for the detection of Chlorine ionic lines . The detection limit of Cl II 479.4 nm is 5 ppm and Background Equivalent Concentration (B .E.C.) is 0.005%. Initial experiments for the detection of Chlorine in the food material are also observed .