A Method for the Experimental Study of Vibrational Nonequilibrium using Resonant Radiatively Driven Acoustic Waves

摘要

The work studied, experimentally and theoretically, the interaction of radiative and vibrational nonequilibrium in the motion of an infrared-active gas. Specifically, the study was concerned with acoustic waves caused in the infrared-active gas in a closed tube by a periodic input of radiation. The pressure response associated with these waves is measured and is compared with theoretical predictions. The resonant (or tuned) condition, in which the tube length is an integer multiple of one half the classical acoustic wavelength, with corresponding enhanced response, was of primary interest. A new and unique method of measuring resonance profiles of pressure amplitude and phase angle has been developed. These profiles are obtained by varying the wavelength of the acoustic wave about its resonant value. Theoretical solutions were obtained for the phenomena under study in the experiment, with particular emphasis on the interpretation of the measured resonance-profile information. The solutions are obtained by application of a basic model for the coupling of radiative and vibrational nonequilibrium in an infrared-active diatomic gas, developed in recent work by Gilles and Vincenti. Two types of solutions are discussed. Experiments were performed in pure CO2 and in various mixtures of CO with other gases. (Author)