Laser ablation molecular isotopic spectrometry (LAMIS): current state of the art
Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is a direct and rapid technique that measures optical emission in laser-induced plasmas for isotopic analysis. LAMIS exploits relatively large isotope shifts in spectra of transient molecular isotopologues formed in laser ablation plasma. LAMIS can be performed without sample preparation at atmospheric pressure in open air or inert buffer gases. A spectrometer with modest spectral resolution can be suitable for both LIBS and LAMIS techniques, and thus elemental and isotopic measurements can be accomplished on the same instrument. To date, detection of several isotopes (H, B, C, N, O, Cl, Sr, and Zr) in laser ablation plumes was demonstrated. Precision of quantitative LAMIS measurements was within 9‰ for the 10B/11B ratio determined with confidence of 95% (2σ-interval). Simultaneous determination of isotopes of different elements was shown to be physically possible, while determination of several isotopes of the same element was successfully demonstrated (Sr, Zr). The studies on double-pulse LAMIS and femtosecond LAMIS indicated further prospects for improving accuracy and sensitivity in this technique. A possibility of semi-quantitative isotopic analysis at distances up to 7.8 m without using calibration standards was demonstrated. The latter technique was named as Femtosecond Filament-induced Laser Ablation Molecular Isotopic Spectrometry (F2-LAMIS). Application of LAMIS in industrial, laboratory, and field operations is possible; and such measurements can be realized at a standoff distance to the sample.