Chemistry and physics of cosmic nano- and micro-particles
Small solid particles represent an important and ubiquitous component of our and other galaxies and determine their overall spectral appearance. Although they constitute only a minor ingredient by mass, they control the thermal, dynamical, chemical, and ionization state of the cool and densephases of the interstellar medium. The grains are produced in the massive outflows of evolved stars, modified by shocks and radiative processing in the diffuse interstellar medium, and grow by accretion of ice mantles and coagulation in the dense cores of molecular clouds. The last step in their lifecycle is consumption by forming stars or their incorporation into planets. Cosmic dust particles are an extremely exciting system if one is interested in the formation routes from gas phase molecules to solids, the optical behaviour of small particles, and surface chemistry. Astronomical spectroscopy, together with dedicated laboratory studies, has led to the identification of carbonaceous solids, silicates, and different forms of ices in the Milky Way.