MEASUREMENT OF C2F4CL2, CCL4, CHF3 AND O2 BY WAVELENGTH MODULATION LASER ATOMIC-ABSORPTION SPECTROSCOPY OF EXCITED CL, F AND O IN A DC DISCHARGE APPLYING SEMICONDUCTOR DIODE-LASERS

The concentrations of C2F4Cl2 and CCl4, CHF3 and C2F4Cl2, and O2 have been measured in a dc ps discharge by wavelength modulation laser abso rption spectroscopy of excited chlorine, fluorine and oxygen, respecti vely, applying semiconductor diode lasers. Argon and helium at reduced pressure were used as plasma gases. Preliminary 3sigma detection limi ts of 0.6-1.5 ppb for chlorine compounds by absorption of the Cl 837.6 0 nm line, about 70 ppb of fluorine compounds by the F 739.87 nm line, and about 20 ppb oxygen molecules by the O 777.18 nm line were found.