화학공학소재연구정보센터
Journal of Physical Chemistry, Vol.99, No.37, 13652-13658, 1995
Vector Correlations in the 193 nm Photodissociation of the No Dimer
We have studied photodissociation at 193 nm of the NO dimer, which has cis planar geometry. The photofragment NO(A(2) Sigma(+)) was detected by laser-induced fluorescence using the E(2) Sigma(+)-A(2) Sigma(+) transition around 600 nm. The recoil anisotropy beta and the v-J correlation have been determined at several rotational levels N by analyzing Doppler profiles of the rotational line measured at six different geometries of linearly polarized photolysis and probe lasers. The values of beta and the v-J correlation indicate that the relations of three vectors (mu(abs), v, and N) reach the Limiting case of mu(abs)parallel to v and v perpendicular to N as N increases. Taking account of the result of the rotational alignment A(0)((2)) measured previously, we conclude that this dissociation proceeds mostly within the parent molecular plane. In the photodissociation of van der Waals molecules, the presence of low-frequency van der Waals vibrations accelerates the available energy dissipation from the N-N bond, where most of the energy is located after photoexcitation, to other vibrational modes. Since this energy randomization transfers a fraction of energy into the torsional motion, angular momentum not perpendicular to the original molecular plane is produced. As a result, the rotational alignment A(0)((2)) and the v-J correlation deviate from their limiting values, particularly at lower N.