Effects of the Molecular Conformational Changes of N,N-dimethylnitrosamine (CH3)2NNO (DMN) on Vector Correlations
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Photodissociation dynamics investigate the microscopic details of chemical reactions. We carried out an investigation to determine whether a predicted conformation change in the excited state of N,N-dimethylnitrosamine (DMN) will result in a propeller-like trajectory of the ejected NO product. DMN was photodissociated at 355 nm in a velocity-mapped ion imaging apparatus. Vector correlations between and among the transition dipole of the parent molecule, angular momentum of the NO fragments, and velocity of the NO fragments were measured. The correlation between the velocity v and angular momentum j in DMN is almost zero; though, the μ-v correlation is about -0.20 indicative of prompt dissociation. This is explained by the N-N bond stretching and causing a conformational change to occur where NO puckers toward the methyl groups upon excitation. The conformational change from planar to pyramidal around the C2NNO frame of the parent molecule removes a barrier to N-N scission. A low energy internal torsional mode around the N-N bond minimized the μ-j correlation. We speculate that the NO rotating out of the plane in addition the puckering leads to DMN having both propeller- and Frisbee-like motions.