Temperature and Emission Spatial Profiles of Laser-Induced Plasmas during Ablation Using Time-Integrated Emission Spectroscopy

Abstract

Emission spectra and excitation temperature spatial profiles, within laser-induced plasmas from solid copper targets, are characterized as a function of laser power density with the use of time-integrated emission spectroscopy. This research shows how the measured axial spatial emission intensity of the expanding plasma can be influenced by the time integration. The excitation temperatures calculated from these integrated emission-line intensities may not coincide with the actual temperature spatial profile. Transient plasma dynamics during time-integrated intensity measurements can influence both the excitation temperature and the atomic number density of the emitting species. As a demonstration of the influence of fluid dynamics on time-integrated emission measurements, a shock-wave model was used as an example to show how the spatial emission intensity profile of a laser-induced plasma can be affected by transient expansion. Even for time-resolved emission measurements, the high velocity of a laser-induced plasma can influence spatial intensity data close to the target surface. The ability to accurately measure spatial emission intensity and temperature behavior is shown to be related to the integration time vs. plasma expansion velocity.