The infrared multiphoton excitation and photochemistry of DN₃

Multiphoton excitation and dissociation of DN₃ by short CO ₂ laser pulses is shown to be a collisionless process. The characteristic features of this multiphoton process are systematically studied. The average number of photons absorbed per DN₃ molecule and the absolute dissociation yield show a strong dependence on the peak laser intensity. Resonantly enhanced coherent multiphoton excitation, rather than stepwise incoherent excitation, is suggested. The primary dissociation products of DN₃ are ND[¹Δ] and N₂. Formation of vibrationally excited ND[¹Δ] intermediates is suggested. The reactions of ND[¹Δ] with DN₃ lead to chemiluminescent signals originating from the formation of electronically excited ND₂[²A₁] and ND[³Π]. Formation of the ND[³Π] intermediate is attributed to a reaction of ND[¹Δ] and vibrationally excited DN*₃ molecules: ND[¹Δ]+DN*₃→ND[ ³Π]+ND[³Σ^-]+N₂.