O(1S) Effective Lifetimes

Metadata record for data from ASAC Project 43
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From the abstract of the referenced paper:

Intensity time-series with a 0.05 s time resolution were obtained for the 428 nm N2+ (1NG) band and 558 nm O(1S) line emissions during intervals of rapidly fluctuating auroral intensities at Macquarie Island during 1988. Similar measurements have been used by previous workers to infer the effective lifetimes of the O(1S) state and the existence of, and percentage contribution from, an indirect excitation process. Using 'constructed data' and an impulse function analysis technique, we introduce a method of analysis that shows that variations in the energy of the precipitating auroral electrons during the intensity fluctuations may be misinterpreted as an indirect excitation process of low percentage contribution. Subsequent to our analysis of the data presented here, we became aware of 'pulse pile-up' contaminations of our raw data files. We have not corrected for this in the examples presented. However, our analysis shows that noise on the intensity time-series by itself, or in combination with the energy fluctuations, may result in a significant over-estimation of the contribution of an indirect excitation process. Measurement of the O(1S) effective lifetime is accurate to within 0.05 s.

The method we introduce allows determination of an upper limit for the misinterpretation as an indirect process of non-linearites known to exist between the 428 nm N2+ (1NG) band and and 558 nm O(1S) line emissions. These non-linearites have been ignored in previous investigations of O(1S) excitation processes.