Laser spectroscopic characterization of single extraterrestrial dust particles using optical trapping-cavity ringdown and Raman spectroscopy

Earth's atmosphere contains interplanetary dust particles (IDPs), which are a key ingredient to understand planetary phenomena, yet the study of their physicochemical properties without external interferences at the single-particle level is limited. With the optical-trapping (OT) technique, a single dust particle can be stably trapped in air for subsequent characterization. We report on measurements of the single-particle extinction of trapped particles using cavity ringdown spectroscopy at ultraviolet wavelength around 308 nm. We also present Raman spectral features of chemical groups in individually trapped particles. Two simulants of extraterrestrial materials, (Martian and lunar analogs) along with carbon spheres and volcanic ashes were trapped and spectroscopically characterized. In addition to the on-trap measurements, the particles' morphological and mineralogical information was obtained from offtrap measurements using scanning electron microscopy and energy dispersive spectroscopy. This study demonstrates that the integration of OT with cavity ringdown and Raman spectroscopy provides a new tool to gain multimodal information on the physicochemical properties of single IDPs with minimum to no external interferences. (c) 2020 Elsevier Ltd. All rights reserved.