Remote molecular composition analysis of laser-ablated material

Abstract

Abstract A novel method is described for remotely interrogating bulk molecular composition of rocky materials. Laser energy heats a local area on the substrate; flux is optimized to melt and evaporate target constituents with low rates of molecular dissociation. Substrate temperature rises until an equilibrium is established between incident flux and latent phase-change energies, reaching ˜2500 K in vacuum. A blackbody signal is emitted by the heated spot, traveling outward through the evaporated material; reflective optics direct the signal into a spectrometer. Ro-vibrational absorption in the plume provides a diagnostic for identifying bulk molecular composition of the substrate. Absorption spectra are modeled for compounds with available a priori molecular cross-sections, based on laser and receiver characteristics, and target material properties. Mass ejection flux drives the plume density profile. Qualitative, species-specific spectral profiles are derived by integrating molecular cross section along a path through the plume. Simulations indicate robust absorption profiles.