Velocity Map Ion Imaging of Chlorine Azide Photolysis:  Evidence for Photolytic Production of Cyclic-N₃

Abstract

The method of velocity map imaging was applied to study the photodissociation dynamics of ClN 3 near 235 nm under collision-free conditions. Derived kinetic energy distributions of state-selected Cl ( 2 P J ) provide a medium-resolution energy spectrum of the N 3 fragment. Markedly bimodal distributions are observed that suggest simultaneous formation of the linear-N 3 (X ˜2Π) isomer as well as an energetic form of N 3 , consistent with recent theoretical predictions of a cyclic isomer, resembling an isosceles triangle. Angular distributions of the photofragments indicate that 2 1 A′ r 1 1 A′ excitation is the most important pathway to photoproducts. Branching ratio measurements between the dominant spin-orbit excited-state Cl* ( 2 P 1/2 ) and the spin-orbit ground-state Cl ( 2 P 3/2 ) showed Cl*/Cl ≈ 0.8/0.2. The branching ratio between linear-N 3 and cyclic-N 3 formation was determined to be ≈ 0.8/0.2.

Spectroscopy of free radicals and radical containing entrance-channel complexes in superfluid helium nanodroplets

“…The N 3 and N 4 molecules have been predicted [214][215][216] and observed experimentally [217,218]. The cluster formation mechanism in helium droplets described above should allow one to produce a wide variety of such metastable N n systems from nitrogen atoms, where n could be much larger than 3 and is solely determined by the N-atom density in the pick-up region.…”

Theoretical Design of Green Energetic Materials: Predicting Stability, Detection, Synthesis and Performance

“…However, despite extensive theoretical and experimental efforts, N 2 remains the only form of nitrogen that has been isolated at room temperature. Linear and cyclic N 3 , as well as an open-chain form of N 4 , have been detected experimentally, but they are too unstable to be of any direct interest for applications [70][71][72]. The synthesis of N 5 + and the subsequent detection of N 5 − [55][56][57], spawned interest in N 8 and N 10 in the form of molecular salts.…”

“…The first experimental evidence of the N 3 (C 2v ) came in 2003 from Hansen and Wodtke [71]. They studied the photodissociation of chlorine azide (ClN 3 ) near 235 nm under collision-free conditions, and were able to demonstrate the formation of two isomers of N 3 , that is linear and cyclic N 3 .…”

Searching for ways to create energetic materials based on polynitrogen compounds (review)

“…The bond length between the neighboring nitrogen atoms in the N 3 radical, which was measured in [50] to be equal to 1.1815Å, was calculated theoretically [15] only 40 years later, in 2005. At approximately the same time, an analysis [51,52] of experimental data on the photolysis of ClN 3 exposed to ultraviolet radiation (λ = 235 nm) led to the hypothesis about the existence of a cyclic isomer of N 3 . The energy spectrum of the decomposition products of ClN 3 contained a contribution from slow N 3 , called HEF-N 3 (a high-energy form of N 3 ).…”