Laser ablation molecular isotopic spectrometry for analysis of OD/OH isotopologues in plasma

Abstract

Laser ablation molecular isotopic spectrometry (LAMIS) was recently reported for isotope analysis of samples and for molecules formation mechanism investigation by analyzing the isotopologues in laser induced plasma. LAMIS was utilized to quantify the OD and OH molecules in fs-laser ablated plasma from moist water samples carried by pure Ar gas at ambient environment. A theoretical spectral fitting model for OD and OH molecules was developed and was used to extract the isotopic ratio OD/OH by fitting of experimental spectra. Time-resolved spectra were measured and the influences of spectrum intensity and signal to noise ratio (SNR) on isotopic quantitative analysis performance were evaluated. The relative concentration of OD and OH molecules in laser induced plasma from a set of water samples with D2O concentrations in the range of 0% to 99.8% are quantified, and a very good linear relationship between D concentration and D2O concentration was obtained. The linear curve exhibited R2 exceeding 0.9997 and a slope of 1.006. In addition, no standard sample is necessary for quantitative analysis, demonstrating the advantages of spectral fitting LAMIS.