title: Raman spectroscopy of hypersonic shock waves
abstract: Raman spectroscopy is shown to be an efficient diagnostic methodology for the study of hypersonic shock waves. As a test, absolute density and rotational population profiles have been measured across five representative normal shock waves of N2 generated in a free jet, spanning the Mach number range 7.7<M<15.3. The interconversion of three differentiated populations (cold, scattered, and rethermalized molecules) across these shock waves shows a largely bimodal rotational distribution function with additional contribution of scattered molecules, in close analogy with the velocity distribution function known from helium shock waves [G. Pham-Van-Diep et al., Science 245, 624 (1989)]. Quantitative data on invariance trends of density profiles and properties of the wake beyond the shock waves are reported.
authors.affiliation: Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid, Spain.
authors.initials: A
authors.lastname: Ramos
authors.initials: B
authors.lastname: Mate
authors.initials: G
authors.lastname: Tejeda
authors.initials: JM
authors.lastname: Fernandez
authors.initials: S
authors.lastname: Montero