Vibrational Raman Spectra of Micro-Droplets and Micro-Crystals of Nitrogen Formed in Free Jet Expansions

摘要

Stimulated Raman loss spectroscopy (SRLS) has been used in a study of very large aggregates of N2 (estimated 1,000,000- 10 to the 9th molecules) produced by expansion from a channel nozzle. By probing at different distances from the nozzle opening, well-defined frequency shifts are observed which characterize gas-liquid, liquid-solid, and beta-to alpha-solid phase transitions. The internal temperature of the aggregates, the rotational temperature of the monomer, and the approximate monomer/aggregates ratio were also determined. This is the first application of non-linear Raman techniques to the observation of phase transitions in jet expansions. Reprints.(mjm)