Collision Energy Dependence of the Overall Rate Constant for the Reaction NH(a1Δ ) + HN₃

Abstract

The overall rate constant for the reaction NH(a1Δ ) + HN₃ has been determined by the laser photolysis of hydrogen azide (HN₃) at 266 nm and 193nm. The visible emission from vibronically excited NH₂(A˜²A₁) was dispersed and its time-dependent profiles were measured at several wavelengths. The rate constants are dependent not only on the photolysis wavelengths but also on the vibrational levels of the NH₂(A˜²A₁) produced in the reaction. The intermolecular potential between NH(a1Δ) and HN₃ was determined to be the form V(R) = –C/R^s (2 < s < 4, C: constant) from the analysis with a long-range potential approximation. The interaction between NH(a1Δ ) and HN₃ is mainly governed by the dipoledipole interaction in the initial stage of the reaction.