Photodissociation of N2O:  J -dependent anisotropy revealed in N2 photofragment images

Photofragment imaging is used to measure the state-specific angular distributions of N2 produced in the ultraviolet photodissociation of N2O. 2+1 REMPI (resonance enhanced multiphoton ionization) through the a″(1Σg+) state is used to ionize individual rotational states of N2(ν=0) between J=40 and J=90 produced when N2O is dissociated by light of approximately 203 nm. The anisotropy parameter, β, used to characterize the angular distributions of the N2 ion images, is greater than one for the lower rotational levels probed, and decreases to approximately zero for the highest rotational levels of N2. The positive beta parameter indicates that the products arise primarily from a parallel transition to the 2 1A′(1Δ) state in the parent molecule, and the decrease in β with increasing J of N2 is due to increased bending in the parent N2O during dissociation. The ion images also allow us to assign transitions in a spectroscopically perturbed region of the N2 photofragment REMPI spectrum and to reveal the production of N2 products in the first vibrationally excited state.