Ab initio potential energy surfaces, total absorption cross sections, and product quantum state distributions for the low-lying electronic states of N 2 O Resonance Raman spectra measured for ClNO photoexcited at 212.5, 219, and 222 nm produce evidence that the strong transition at the vacuum ultraviolet end of the merged A band system dominates to wavelengths as long as 222 nm. The spectral resolution is sufficient to enable definitive assignments of excited vibrational levels in the ground electronic state, several of which have not been previously observed. A curvilinear coordinate model of the ground state potential surface around the Franck-Condon region has been constructed. This model yields vibrational eigenvalues in excellent agreement with all known transitions.

A spectroscopic analyzer has been developed for rapid, accurate quantification of acetylene and methyl acetylene in hydrocarbon cracked gas processing plants. The system utilizes off-axis integrated output cavity spectroscopy to measure the near-infrared, cavity-enhanced absorption spectrum of ethylene, methyl acetylene, and acetylene and employs a chemometric data analysis strategy to quantify the respective constituents. Initial tests verified that the instrument is capable of measuring, <0.050 ppmv of acetylene, has a precision of +/-0.025 ppmv, and can accurately determine acetylene concentrations with comparable accuracy to a gas chromatograph (+/-0.1 ppmv) in an actual process stream composition matrix under plant operating conditions. Subsequently, the prototype analyzer was installed in a hydrocarbon facility for field-trials, where its rapid response (< or =30 seconds or better) allowed it to measure transient acetylene and methyl acetylene fluctuations that were too fast for conventional methodologies. Moreover, the analyzer showed an extended dynamic range that enabled measurement of very high acetylene levels (0-1000 ppmv) during abnormal plant operations. Finally, two commercial acetylene analyzer systems with stream-switching capabilities were implemented in an industrial facility and initial results are presented.

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