The formation of N(2)O nanoparticles in a collisional cooling cell between 4 and 110 K

Abstract

N(2)O (CO(2)) particles covering a vast size range from some nanometres up to some hundred nanometres were formed by injecting gaseous N(2)O (CO(2)) into a collisional cooling cell at temperatures between 4 and 110 K. FTIR spectroscopy was used to study the vibrational dynamics of the nanoparticles between about 600 and 4000 cm(-1). For the spectra of the bigger particles formed at temperatures around 78 K, we have studied the influence of the experimental conditions on the fine structure of the strong absorption bands and its temporal behavior. From an estimate of the particle sizes, we conclude that the observed changes in the fine structure are not simple size effects; they are likely to be due to a change in the particle shape or in the molecular order. From a comparison with infrared spectra of clusters generated in a supersonic jet expansion, we estimate the size of the particles produced at temperatures below 10 K to lie around one nanometre.