| Popis: |
Spectrally resolved vacuum ultraviolet radiation measurements of the continuum arising from the recombination of electrons with N+ and C+ ions have been made using a high-purity shock tube to generate the radiating source. Mixtures of neon and nitrogen or carbon monoxide were used as the test gas, with the radiation observed behind the reflected shock at temperatures of 12,500–13,000°K. Experiments were performed wherein the shocked gas ranged from optically thin to blackbody conditions, from which photoionization cross sections for both N and C were obtained between 700 A and 1100 A. In this wavelength range, the use of windows is precluded. The attendant problems and unique features of the instrumentation designed for these experiments are described. They include a multi-channel spectrometer and an explosively driven windowless plunger which couples the spectrometer to the shock tube. The measured cross-section values are compared with other available experimental values and theoretical predictions. Agreement in the results for nitrogen is taken to validate the technique. No other experimental values were found for carbon, where the measurements yield a cross section approximately twice that obtained from theoretical calculations. |
