Measurements of Cl-atom photofragment angular momentum distributions in the photodissociation of Cl2 and ICl

We have studied the complete Cl-atom molecular-frame photofragment angular momentum distributions from the photodissociation of Cl2 and ICl in the 320–560 nm region using time-of-flight mass spectroscopy with laser detection. The experimental signals were analyzed using the polarization-parameter formalism described in the preceding paper. These experiments study three distinct cases. The first case is the 470 nm dissociation of Cl2 through the B 3Π0+u state accessed via a parallel transition, yielding Cl-atom photofragments with polarizations described by the single parameter a0(2)(∥)=−0.7±0.2. The second case is the 320 nm dissociation of Cl2 through the C 1Π1u state accessed via a perpendicular transition, yielding Cl-atom photofragments with polarizations described by the two parameters a0(2)(⊥)=−0.50±0.10 and a2(2)(⊥)=−0.32±0.06. The third case is the dissociation of ICl in the 490–560 nm region in which dissociative states of both parallel and perpendicular character are accessed. In this wavelength region, the polarizations of the resulting Cl-atom photofragments are completely described by the approximately constant incoherent parameters, a0(2)(∥)≈+0.4, a0(2)(⊥)≈−0.2, and a2(2)(⊥)≈−0.2, whereas the interference contributions to the polarization, the Im[a1(1)(∥,⊥)] and Re[a1(2)(∥,⊥)], oscillate sinusoidally with excitation wavelength in a fashion that is sensitive to the shapes of the dissociative surfaces.