Quantitative spectroscopy of low temperature magnesium and titanium plasma plumes

Simultaneous absorption spectroscopy and laser induced fluorescence measurements were used to map the densities of monatomic species within KrF laser produced magnesium and titanium plasma plumes expanding in vacuum. Density contour plots of ground state Mg I and Mg II species were obtained for five slices within a magnesium plasma at a delay of lRs and for a laser fluence of (2.0 #+-# 0.2)Jcm"-"2. Peak densities of the order of 10"1"2-10"1"3 cm"-"3 were detected for both species beyond 14 mm. from target. Closer to target the peak optical densities exceeded the limit of the detection system, however by fitting Voigt profiles to the wings of the absorption lineshapes the Mg I number densities, in this region, were estimated to be >10"1"4 cm"-"3 This value agrees with the estimation obtained by 'regressing' spatial absorption profiles recorded at long delay times. The populations within a number of Ti I and Ti II levels were investigated for a laser fluence of approximately (5.1 #+-# 0.2)Jcm"-"2 . Density contour plots were produced for delay times of 0.6, 0.9 and 1.4 #mu#s. The peak density of the ground state Ti I level at 0.9 #mu#s was in good agreement with that predicted for ground state Mg I at 1 #mu#s. TOF distributions of ground state Ti II levels were consistent with a free expansion over the laser fluence range (2.5 - 9)Jcm"-"2 . A Langmuir probe was used to determine the free electron TOF distribution within titanium plasmas, which was found to contain two peaks. The integrated fluxes of free electrons and ground state Ti II species, measured using a Langmuir probe and absorption spectroscopy / LIF respectively, were in excellent agreement, demonstrating consistency of results derived from three different diagnostics. (author)Available from British Library Document Supply Centre-DSC:DXN030969 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo