Characterisation of CN in the photodissociation of cyanogen azide at 193 nm

Abstract

The photodissociation dynamics of NCN3 has been investigated by observation of the CN(X2Σ) product molecule. The CN fragment is formed in vibrational states ν = 0,1,2 with a population ratio of P(ν = 0):P(ν = 1):P(ν = 2) = 0.42:0.33:0.25. The rotational state distribution is broad, a Boltzmann plot shows a nonlinear behavior. The rotational excitation carries 9% of the available energy. The CN recoil velocity distribution is also broad and indicates a significant internal excitation of the N3 product molecule. The spin is distributed statistically. The fragmentation does not proceed in the Franck‐Condon limit but strong forces act on the upper potential energy surface.

The story of NCN as a key species in prompt-NO formation

“…Depending on the photolysis wavelength, the reported primary photodissociation products are 1 NCN as the dominant species under most experimental conditions and CN in case of short photolysis wavelengths of   193 nm [125,126]. Another direct dissociation pathway forming 3 NCN, as mentioned in Refs.…”

“…3 NCN( Σ ) + N 2 ( 3 ) has been suggested [125,126]. At room temperature and pressures of a few hPa, however, 3 NCN formation is markedly delayed by more than 100 s, showing that subsequent processes such as collision-induced ISC and collisional cooling are significant for the overall relaxation process (see also Section 5.2).…”

“…The UV photolysis of NCN 3 served as a precursor for many spectroscopic studies [2,4,5,63,67,88,125,126]. The absorption peak at 220 nm corresponds to S 1 ← S 0 excitation [123].…”

Kinetics of the NCN + NO Reaction over a Broad Temperature and Pressure Range

“…The experiments were performed employing the pulsed laser photolysis/laser-induced fluorescence technique in two different quasi-static reactors (see below) with helium as the bath gas. The NCN species was produced from NCN 3 − at 193 or 248 nm with an ArF or KrF excimer laser, respectively. Upper limits (see below) of the NCN 3 concentration ranged from 2 × 10 12 to 1 × 10 14 cm –3 in the low-pressure experiments, and 3 × 10 14 to 2 × 10 16 cm –3 in the high-pressure experiments.…”