Photodissociation Dynamics Of H/DN₃ And C₅H₅N And Reaction Dynamics Of D+H₂

Photodissociation dynamics of H/DN₃ in the 188nm-266nm were investigated using H atom Rydberg tagging time-of-flight (HRTOF) method. From the results we found that:1) In the 266nm to 225nm region, clear vibration structures can be assigned to symmetric stretching mode (V₁,0,0) and combined with one and two quanta of bending motion [(V₁,l,0) and (V₁,2,0)]. The dissociation energy of H/DN₃ are 30910cm^-1 and 31620cm^-1, respectively. The anisotropy parameters of product here (all near -0.7) indicate a perpendicular electronic transition and a rapid dissociation.2) In the 220nm to 196nm region, a second H-atom producing channel grows whose translational energy release is consistent with cyclic-N3 formation. High level ab initio quantum chemical calculations reveal a transition state to cyclization of the N3 moiety in H(D)N₃ on the S₁ surface that is close in energy to the experimentally observed threshold energy. A conical intersection between the S₂- and the Si-state quite close to this transition state. Passing over this transition state leads to an electronically excited, non-planar, cyclic HN3 intermediate which theory shows can dissociate to cyclic-N3. This work provides the clearest presently available insights into how ring closure can occur in azide photochemistry.3) When the dissociation energy becomes higher, the second H-atom producing channel becomes small and disappears in the end. The anisotropy parameter is energy-dependent and decreased with the dissociation wavelength. These dynamic informations suggest that photodissociation proceeds via multiple dissociation pathways on different excited electronic states of H/DN3.The Dynamics of the D+H₂→HD +H Reaction was studied with collision energy E_c=0.315, 0.484, 0.783, 0.973eV by HRTOF method. The effect of reagent rotation on the D+ #2 reaction was found unexpectedly in our result, and the effection becomes more pronounced at higher Eq. A theoretical simulation is carried out using a fully converged coupled channel scattering calculation that employed the highly accurate BKMP2-PES. With a state-to-state-to-state (SSS) model, we reveal that the reagent. rotation effect on the dynamics was traced to the selection of the quantum bottleneck states through reagent orientation, thus suggesting a novel strategy to control the transition state pathways in direct chemical reactions.Using a femtosecond two-color pump-probe time-of-flight mass spectrometer, the decay dynamics of excited pyridine (C5H5N) is investigated in real time by (1+2') multiphoton ionization detection. The lifetime constant of the Si state at pump wavelength 265nm is determined to be 3.3 ± O.lps.