Shock Excitation of Solid Aromatic Hydrocarbons

Abstract

SHOCK excitation of a wide range of powdered inorganic solids (mainly metallic oxides) by helium driven shock-waves in argon1 has not only provided a powerful means of producing relatively clean spectra of astrophysically important diatomic molecules2, but also has given some insight into the physical processes which take place when the powder particles undergo severe thermal transients. From the general observation that molecular spectra alone are excited (in the hot stagnant region behind the reflected shock wave) at low temperatures (∼2,000° K.), mixed molecular and atomic spectra are excited at intermediate temperatures (∼5,000° K.) and entirely atomic spectra are excited at high temperatures (∼10,000° K.), and from other experimental considerations (refs. 1a and 1c), it is thought that a predominantly atomic vapour is evaporated from the solid inorganic surfaces, which, if the temperature is low enough, partially or completely recombines to form diatomic species. It is therefore a logical extension of this work to examine the variation with environmental temperature of the spectra from shock excitation of powdered organic materials, and in this communication experiments with benzene, naphthalene, and anthracene are discussed.