The efficiency of CO vibrational excitation in a self-sustained CW glow discharge

The fraction of the electrical power which is placed into the vibrational energy mode of CO by a CW, aerodynamically stabilized, glow discharge has been found to decrease from 76 to 30 percent as the input energy increases from zero to 0.8 eV per CO molecule. The remaining energy is measured as being lost to gas heating within the discharge. In the first of the two experiments reported here, the vibrational energy was transferred into stream heating by collisions of the excited CO molecules with aluminum screening. The resulting heating was used to determine the energy in CO vibration. In the second experiment, the relative intensities of the spontaneous emission from the overtone bands of CO were used to determine the vibrational energy content of the CO. The results of the two measurements agreed well. The fraction of power entering vibration was found to depend on the energy loading per CO molecule, independent of He diluent concentration, total pressure, or nearness to the arcing limit. The maximum energy which can be stored in vibration for this self-sustained discharge was found to be approximately 0.25 eV/CO molecule.