Abstrakt

Infrared and uv/visible emission spectroscopic studies of laser generated carbon plasmas

Laszlo Nemes

Time –resolved carbon plasmas were generated from a graphite target using the 1064 nm radiation of a Q-switched YAG laser. At long time delays from the laser pulse (from 1 to 10 microsecond) the spectral emission was detected simultaneously by a UV/visible and an infrared spectrometer. The spectra were de-noised and background corrected for thermal radiation. Spectra were taken in various gaseous environments (helium, argon and nitrogen) and were analyzed for molecular temperatures assuming local thermal equilibrium. The spectra contained broad spectral features, the width being determined by the applied spectral resolution (about 80 nm), thermal collision broadening and molecular spectral band width. The UV/visible spectra were composed of atomic emission lines from the environmental gases and the graphite target, as well as diatomic bands due to carbon. Tentative molecular and atomic assignments of the infrared spectra were made using published spectral databanks, theoretical calculations and spectral literature. The results are interesting for several fields, such as remote chemical analysis, study of carbon clusters (graphene, fullerenes and linear carbon molecules) as well as from the point of thermal excitation of molecules in such plasmas. They may also have interest for astrophysics of cosmic carbon molecules.