Photophysics and Photochemistry of Ethanedinitrile and the Cyanide Radical
Abstract
Ethanedinitrile is a simple tetra-atomic molecule. The absorption spectra have been measured in the 150 ~ 230 nm region from the rm C^1Pi_{u} >=ts X ^1Sigma_{g}^+, B ^1Delta_{u} >=ts X ^1Sigma_{g }^+ and rm A ^1 Sigma_{u}^- >=ts X ^1Sigma_{g}^+ transitions. The excitation, fluorescence and photolysis yield spectra have been obtained above 206 nm. Radiative lifetimes, quenching rates, emission and dissociation quantum yields have been determined for most vibrational levels in the rm A ^1Sigma_ {u}^- electronic state. In addition, rm C_2N_2 was photolyzed at 193 nm. Populations in the F_1 and F_2 fine-structure components of nascent CN (X ^2Sigma^+, v^{''} = 0) photofragments were measured. This information provides a detailed picture of the A ^1 Sigma_{rm u}^- and B ^1Delta_{rm u} electronic states, and hints of the modes of motion connecting ethanedinitrile NCCN to its isomer isocyanogen CNCN. Three methods were used to determine the heat of formation of CN radicals. The average result of the three independent measurements is Delta H_{f}^0(CN) = 435.4 +/- 2.0 kJ/mol. Radiative lifetimes have been measured for the CN A ^2Pi _{i} v^' = 2 cdots 7 vibrational levels. Multi -step cascading processes from the CN A ^2 Pi_{rm i} state were monitored with red emission or rm B ^2Sigma^+ >=ts X ^2Sigma^+ laser-induced fluorescence. Energy transfer rate constants have been measured for several collision partners and vibrational levels of the CN A ^2Pi_{rm i} and X ^2Sigma^+ states. A complete kinetic model for the energy transfer between these two electronic states has been built. The results should find application in modeling CN emissions from flames and astronomical objects, and optimization of CN vibrational and electronic lasers.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1993
- Bibcode:
- 1993PhDT.......134H
- Keywords:
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- ISOCYANOGEN;
- Chemistry: Physical; Physics: Molecular