Carbon isotope separation and molecular formation in laser-induced plasmas by laser ablation molecular isotopic spectrometry.

ABSTRACT

Laser ablation molecular isotopic spectrometry (LAMIS) recently was reported for rapid isotopic analysis by measuring molecular emission from laser-induced plasmas at atmospheric pressure. This research utilized the LAMIS approach to study C2 molecular formation from laser ablation of carbon isotopic samples in a neon gas environment at 0.1 MPa. The isotopic shift for the Swan system of the C2 Δν = 1 band was chosen for carbon isotope analysis. Temporal and spatial resolved measurements of (12)C2, (12)C(13)C, and (13)C2 show that C2 forms from recombination reactions in the plasma. A theoretical simulation was used to determine the temperature from the molecular bands and to extract the isotopic ratio of (12)C/(13)C derived from (12)C2, (12)C(13)C, and (13)C2. Our data show that the ratio of (12)C/(13)C varies with time after the laser pulse and with distance above the sample. (12)C/(13)C deviates from the nominal ratio (21) at early times and closest to the sample surface. These measurements provide understanding of the chemical processes in the laser plasma and analytical improvement using LAMIS.