Laser-Induced Plasma Acoustics and Laser-Induced Breakdown Spectroscopy: A Happy Marriage

Abstract

The relevance of laser-induced plasmas acoustics (LIPAc) investigations has skyrocketed in recent times, raised by NASA´s mission Mars 2020 research with the Mars Microphone. While LIPAc signal had been succinctly studied and applied, preferably, as a normalization asset to alleviate the shot-to-shot instability of the LIBS signal, knowledge about the structure and the components of the acoustic response, the effect that different parameters may had on it, as well as its behaviour in different scenarios, were yet unknowns on the background of the phenomenon. Research herein focused first on the progress know-how of the LIPAc signal. The conditioning of sample-associated traits, instrumental variables, operational conditions, as well as the target-surroundings on the ensuing acoustic response has been evaluated. Even experiments inside a thermal-vacuum chamber (TVC), a facility that allows mimic planetary environments, have allowed LIPAc signal performance under non-standard atmospheres. From all this, applicability of LIPAC has been demonstrated. The close link that the acoustic response maintains with the physical properties of the sample has made it possible to exploit its use to differentiate specimens that showed a very high similarity in the optical response of their plasmas, to enhance the identification of subsets within a whole, and even to correct discrepancies between atomic and ionic information derived from the matrix effect. In short, the results derived from all these studies go beyond a mere declaration of intentions, demonstrating that the acoustics derived from laser-produced plasmas is a valuable source of information not only acting on its own but also contributing as LIBS-LIPAc combination.