Hook spectroscopy as an atomic number density diagnostic applied to laser-ablated copper plasmas.

摘要

Hook spectroscopy has been used to determine the absolute number density of ground state copper atoms in laser-ablated plasma plumes. An ablation laser power flux of (approximately) 1.5 GW/cm(sup 2) is applied to a solid copper target in a background gas, producing a plasma plume suitable for studying homogeneous copper vapor condensation. Density is measured at post-ablation time delays ranging from 10 (mu)s to 3 ms with 25 torr of argon as the background gas. Planar laser-induced fluorescence (PLEF) images containing relative density information are used in conjunction with the hook spectra to resolve spatially the absolute density within the plume. Copper atom densities thus measured ranged from 1.9 (times) 10(sup 15) cm(sup (minus)3) at a delay of 10 (mu)s to 2.7 (times) 10(sup 13) cm(sup (minus)3) at 3 ms delay in 25 torr of argon The decrease in density is due to the condensation of copper vapor to form fine particulate. As a combustion diagnostic, the hook method may prove extremely useful for the determination of metal impurity density in coal fired flames as well as a single -- shot OH density and temperature diagnostic.