Molecular Desorption by Laser–Driven Acoustic Waves: Analytical Applications and Physical Mechanisms

Abstract

Analytical mass-spectrometry (MS) is a powerful, widely-used tool for materials analysis, helping to make progress in materials and environmental sciences, chemistry, biology, astrophysics, etc (Dass 2007). Often the sample to be studied (analyte) is a solid requiring: a) volatilization/desorption of the analyte atoms/molecules and b) their consequent conversion to the charged particles (ionization) prior to mass analysis. The last two decades have seen revolutionary advances in these techniques (Dass 2007) and the use of direct laser irradiation to achieve volatilization is one of the wide-spread methods (Lubman 1990) These pulsed laser-based techniques for the desorption/emission of the atoms, molecules and ions from the surface of solids has benefitted from fundamental study of the process beginning with the invention of the lasers (Honig and Woolston 1963) . A short laser pulse hitting a solid absorbing surface delivers high energy in a small volume inducing a variety of state changes. One consequence is the evaporation/desorption of surface atoms and molecules could be used for further analysis by MS technique. However, the increasing use of MS methods in analytical chemistry of organic and biomolecules revealed that this direct desorption process had significant drawbacks for the analysis of molecular