Spectrum-Line Reversal Measurements of Free-Electron and Coupled N2 Vibrational Temperatures in Expansion Flows
- 15 December 1965
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 43 (12) , 4434-4443
- https://doi.org/10.1063/1.1696712
Abstract
Spectrum‐line reversal measurements of the excitation temperature of Na atoms in expansion flows of shock‐heated Ar and 1% N2+Ar mixtures are described. The measurements were made in a conical nozzle attached to the end of a conventional shock tube. For expansion flows of pure Ar from reservoir temperatures of 3200° to 4200°K and a reservoir pressure of about 37 atm, the measured Na temperatures (≈2200°K) were considerably in excess of the local‐translational temperature (≈400°K). These high excitation temperatures are interpreted in terms of the excitation of Na by free electrons produced from ionization of the Na in the reservoir. On this basis, free‐electron temperatures are deduced which indicate freezing of the electron thermal energy at values corresponding to those expected at the nozzle throat. This result suggests a slow rate of transfer of electron thermal energy to the Ar translational mode. The addition of 1% N2 to the Ar expansions produced large reductions in the measured Na temperatures. The reduced temperatures are shown to correspond to the frozen N2 vibrational temperatures expected on the basis of previous results. These reductions are explained in terms of an efficient transfer of the excess‐electron thermal energy to the N2 vibrational mode, the free‐electron and N2 vibrational temperatures being thereby coupled and equilibrated during the expansion. The present results also substantiate the faster vibrational relaxation rates inferred previously from similar expansion‐flow studies of pure N2; they further suggest that the simple Landau—Teller rate equation, when used with relaxation times measured in shock‐wave flows, is not adequate to describe the vibrational relaxation process under the extreme nonequilibrium conditions associated with nozzle‐expansion flows.Keywords
This publication has 22 references indexed in Scilit:
- Shock-wave struture in a partially ionized gasJournal of Fluid Mechanics, 1963
- RECENT ADVANCES IN HYPERSONIC FLOW RESEARCHAIAA Journal, 1963
- Excitation of Vibrational and Electronic Levels inby Electron ImpactPhysical Review B, 1962
- A note on the variation of vibrational temperature along a nozzleJournal of Fluid Mechanics, 1962
- Temperature measurements of shock waves and detonations by spectrum-line reversal III. Observations with chromium linesProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1961
- Measurement of Excitation of, CO, and He by Electron ImpactPhysical Review B, 1959
- Approach to equilibrium lonization behind strong shock waves in argonAnnals of Physics, 1957
- The quenching of the resonance radiation of sodiumProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1940
- Über die absolute Ausbeute der Na-D-Linien bei Anregung durch ElektronenstoßAnnalen der Physik, 1935
- Theorie der Streuung langsamer Elektronen an AtomenThe European Physical Journal A, 1931