The photodissociation of N,N-dimethylnitrosamine at 355 nm: The effect of excited-state conformational changes on product vector correlations.

In a photodissociation experiment, the dynamics associated with creating reaction products with specific energies can be understood by a study of the product vector correlations. Upon excitation to the S1 state, N,N-dimethylnitrosamine (DMN) undergoes an excited-state geometry change from planar to pyramidal around the central N. The significant geometry change affects the vector correlations in the photoproducts. Using polarized lasers for 355 nm photodissociation of DMN and for NO photoproduct excitation in a velocity-mapped ion imaging apparatus reveals new vector correlation details among the parent transition dipole (μ), photofragment velocity (v), and photofragment angular momentum (j). The dissociation of DMN displays some μ-v correlation [β0 2 (20)=-0.2], little μ-j correlation [β0 2 (02)∼0], and, surprisingly, a v-j [β0 0 (22)] correlation that depends on the NO lambda doublet probed. The results point to the importance of the initial excited-state conformational change and uncover the presence of two photolysis channels.