Journal of Physical Chemistry A, Vol.114, No.41, 10922-10928, 2010
UV Photodissociation of eta(5)-C5H5NiNO: An Excited-State Jahn-Teller Distortion Produces a Cartwheeling NO
The 225 nm photodissociation of cyclopentadienylnickel nitrosyl was studied using velocity-mapped ion imaging with 1 + 1' REMPI detection of the NO (X-2 Pi(1/2),(3/2), upsilon '' = 0) photofragment. The product recoil energy and angular distributions were measured for selected rotational states of NO. The NO product displays two speeds, a slow product peaked at the center of the ion image and a fast anisotropic product that has an inverted rotational population. In rotational states above J '' = 40.5, an even faster anisotropic NO photofragment appears, most likely because the metal-containing dissociation partner emerges in a lower electronic state, increasing the available energy. The mu-v-j vector correlations were measured and are consistent with the orientation mu vertical bar vertical bar v perpendicular to j. The observed vector correlations arise from an excited-state Jahn-Teller distortion of the parent, a distortion that bends the Ni -NO coordinate prior to dissociation.