The photochemical decomposition of diimide in the gas phase

Abstract

The photodecomposition of trans-diimide, N 2H 2, in its π * ← n + absorption band has been studied in the gas phase at room temperature at wavelengths from 310 to 405 nm, both in the presence and absence of ethylene. Free-radical chain mechanisms are operative in both systems, yielding N 2 + C 2H 6 in the presence of ethylene and N 2 + H 2 in its absence. It is concluded that the primary photodissociation probably occurs from high vibrational levels of the ground state, reached by rapid intersystem crossing directly from the 1B g state originally excited. There is no evidence for collisional de-excitation, and dissociation into N 2H + H or N 2 + 2H probably occurs with a quantum yield close to unity, although some molecular dissociation into N 2 + H 2 cannot be excluded. There is some evidence that N 2H radicals have appreciable stability in the chain reaction systems at room temperature.