To Infinity and Beyond: Diatomic Molecules Above the Dissociation Limit

Speaker: David W. Schwenke, NASA Ames Research Center
July 29, 2014

Presentation

Abstract

An important issue in hypersonic re-entry is the role of diatomic molecules in the radiative transfer from the emission of energetic photons in the shock front to the heat shield. The most intense radiators in Earth re-entry are highly excited nitrogen atoms, with emission in the vacuum ultra violet (VUV). These photons have enough energy to dissociate even the most strongly bound molecules. The spectroscopic data required for the radiative transfer calculations for this situation is incomplete and we have been carrying out first principle calculations of these properties to fill the gaps. In contrast to the situation at lower energy where the density of states is fairly low, good experimental data for validation exists, and only bound-bound transitions are important, in the VUV energy range the density of states as high, good experimental data is not available, and bound-free transitions are involved. The treatment of this regime has necessitated the development of many new techniques for treating these very complex situations, and in this seminar I will discuss the great progress that we have made in predicting the behavior of diatomic molecules above the dissociation limit.

Biography

David W. Schwenke earned a Ph.D. in physical chemistry from the University of Minnesota in 1985, and after a one year CDC Pacer fellowship being essentially the sole user of a Cyber 205, he moved to NASA Ames. In 1988 he was hired as a civil servant, and has been here ever since. He was a 1995 Ames Associate Fellow, a co-winner of the 1999 H. Jullian Allen award, a fellow of the American Physical Society, and a recipient of the NASA Exceptional Scientific Achievement Medal.

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