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• The Thermal Decomposition of NH2 and NH Radicals

J. Deppe, G. Friedrichs, A. Ibrahim, H.-J. Römming, and H.Gg. Wagner
Ber. Bunsenges. Phys. Chem. 102, 1474-1485 (1998)

 

The formation of NH2 and NH radicals as well as H and N atoms during the thermal decomposition of hydrazine was investigated over a wide temperature range. For the first time frequency-modulated spectroscopy was used for the detection of NH2 radicals behind shock waves. In comparison with the dual beam laser absorption technique, the detection limit has been improved by one and a half orders of magnitude.
For reaction (5a) NH2+M → NH+H+M the rate constants were obtained in the temperature range from 2200 to 4000 K

k5a = (1.2±0.5)E15·exp(-(318±10) kJ/mol/RT) cm3/mols

and for reaction (6) NH+M → N+H+M in the temperature range from 2500 to 3400 K

k6 = (1.8±0.8)E14·exp(-(313±15) kJ/mol/RT) cm3/mols.

The experimental apparent activation energies were found to be in good agreement with theoretical calculations and recently recommended enthalpies of formation for NH2 and NH. The competing NH2 decomposition channel (5b) NH2+M → N+H2+M was shown to be of minor importance (<=5%). The kinetic behavior of the unimolecular decomposition of NH2 is compared with that of H2O and triplet-CH2.


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