ABSOLUTE CONCENTRATION MEASUREMENTS OF C-2 IN A DIAMOND CVD REACTOR BY LASER-INDUCED FLUORESCENCE

By use of Laser-Induced Fluorescence (LIF) the absolute concentration of the C-2 radical in a microwave excited diamond chemical vapour depo sition plasma has been measured for the first time. LIF spectra of the d(3) Pi(g)-a(3) Pi(u) (1, 0) Swan band near 473 nm were recorded and synthesized theoretically allowing the plasma temperature of 2100 +/- 200 K to be inferred. Quenching rates were determined from time-resolv ed measurements of the fluorescence decay. By calibrating the LIF dete ction system, using spontaneous Raman scattering in H-2 in the reactor vessel, the absolute concentration of C-2 was determined to be (7.5 /- 1.7) x 10(10) cm(-3). Observations of the C-2 density under varying plasma conditions are reported.