2-PHOTON LASER-INDUCED FLUORESCENCE AND AMPLIFIED SPONTANEOUS EMISSION ATOM CONCENTRATION MEASUREMENTS IN O(2) AND H(2) DISCHARGES

Multiphoton laser-induced fluorescence (LIF) and amplified spontaneous emission (ASE) are used to detect ground-state atoms in oxygen and hy drogen glow discharge plasmas. Experimental results and modeling are a nalyzed to establish the validity criteria for the use of LIF and ASE as diagnostic probes in the measurements of ground-state atom concentr ations. An absolute calibration of the LIF signals is obtained by vacu um ultraviolet absorption experiments, either on the 130 nm resonant l ine of the atomic oxygen, or the 125 nm resonant line of the hydrogen atom. Under typical operating conditions of dc glow discharges, that i s, for gas pressure between 0.5 and 5.0 Torr and discharge current fro m 1 to 50 mA, the densities of the atomic species are measured in the range 10(13) cm-3-10(15) cm-3. Under the same conditions the hydrogen atom temperature varies from (336+/-43) K to (1580+/-90) K.