Sample interview questions: Describe the principles behind laser-induced breakdown spectroscopy and its applications in geology.
Sample answer:
Principles of Laser-Induced Breakdown Spectroscopy (LIBS)
-
Laser Ablation: A high-powered laser pulse is focused onto the sample surface, creating a plasma due to the intense localized energy. This process vaporizes a tiny portion of the material, resulting in the ejection of atoms and molecules into the surrounding atmosphere.
-
Plasma Formation: The ablated material undergoes rapid ionization and excitation due to the high temperature and energy density of the laser pulse. This leads to the formation of a plasma plume consisting of free electrons, ions, excited atoms, and molecules.
-
Emission of Light: As the plasma cools, the excited species return to their ground state by emitting photons of characteristic wavelengths. The intensity of these emitted lines is proportional to the concentration of the corresponding elements in the sample.
-
Spectroscopic Analysis: The emitted light is collected and analyzed using a spectrometer, which separates the light based on wavelength. Each element present in the sample produces a unique spectral signature, allowing for the qualitative and quantitative analysis of the elemental composition.
Applications in Geology
-
Geochemical Analysis: LIBS is used for the rapid and non-destructive analysis of the elemental composition of rocks, minerals, and soils. It provides valuable information for geological mapping, mineral exploration, and understanding the geochemical processes in various geological environments.
-
Provenance Studies: LIBS can determine the elemental signature of sediments and sedimentary rocks, which helps identify their sou… Read full answer