Isotopic analysis of deuterated water via single- and double-pulse laser-induced breakdown spectroscopy

Abstract

Spatial segregation of species presents one of the main challenges in quantitative spectroscopy of laser-produced plasmas, as it may lead to overestimation of the concentration of the heavier species. Analytical capabilities can also be affected by excessive Stark broadening at atmospheric pressure, hindering the ability to spectrally resolve closely spaced spectral lines, such as those belonging to isotopes of the same element. We present an experimental and modeling study of the segregation of species and spectral line broadening in D2O-H2O plasma produced by single- and double-pulse nanosecond laser ablation in air. The ability to resolve Balmer spectral lines of hydrogen and deuterium is investigated by considering the effects of plume segregation. Transient plasma properties which lead to improvements in spectral line separation are discussed. While the plume segregation is found to be negligible in air regardless of the ablation scheme used, we observe a significant improvement in the separation of isotopic spectral lines by employing the double-pulse excitation. This study may lead to increased reliability of optical emission spectroscopy in deuterium-rich plasma environments and suggests the potential for sensitive detection of tritium in air via laser-induced breakdown spectroscopy.