The isothermal flash photolysis of hydrazoic acid

Abstract

Abstract The flash photolysis of HN 3 was studied by coordinated time‐resolved spectroscopic measurements of HN 3 NH( a 1 Δ), NH( X 3 Σ), NH( c 1 π), NH( A 3 π), NH 2 , and N 3 following flash photolysis of mixtures of HN 3 with argon or helium. The primary photolysis is complex, but when the wavelength distribution of the flash is limited to values greater than about 200 nm, the major reactive product is NH( 1 Δ), or states which quickly decay to NH( 1 Δ). Disappearance of NH( 1 Δ) occurs predominantly by the process The process has little, if any, energy of activation, and no detectable dependence on the pressure of inert gas below 1 atm. The rate of formation of NH 2 in its ground vibrational state depends on the inert gas pressure in a way that can be accounted for by vibrational relaxation from initial excited vibrational states. The total amount of NH 2 is roughly comparable with the amount of HN 3 decomposed by primary photolysis. The observed N 3 can be attributed to the NH( 1 Δ) + HN 3 reaction, although a smaller amount could also be formed by primary photolysis. The value of k 2 is revised upward from the value given in a preliminary report on the basis of a more careful consideration of the effects of Beer's law failure in absorption measurements involving narrow spectral lines.