Photodissociation of carbonic dibromide at 267 nm: Observation of three-body dissociation and molecular elimination of Br[sub 2]

Xu, Dadong; Huang, Jianhua; Francisco, Joseph S.; Hansen, Jaron C.; Jackson, William M.
October 2002
Journal of Chemical Physics;10/22/2002, Vol. 117 Issue 16, p7483
Academic Journal
The photodissociation of Br[sub 2]CO around 267 nm has been studied by time-of-flight mass spectroscopy and ion velocity imaging. The atomic (Br and Br[sup *]) and molecular products (Br[sub 2] and BrCO) are detected via multiphoton ionization with the same laser. The results show that the molecule dissociates into (1) Br(fast)+Br(slow)+CO via an asynchronously concerted three-body decay process for both ground and spin-orbit excited bromine atoms, (2) BrCO(A)+Br, and (3) Br[sub 2] + CO, the molecular elimination channel. The translational energy distributions of bromine atoms from reaction (1) are bimodal. For both spin-orbit states the anisotropy parameters differ clearly for slow and fast bromine atoms, where the β values for slow bromine atoms decrease relative to those for fast atoms. The β values for the Br[sub 2] elimination channel almost reach the low limit of -1. Taking into account the translational energy and angular distributions of these reactions, an asynchronously concerted decay mechanism could be proposed for the three-body dissociation. It is concluded that the transition dipole moment is in the direction perpendicular to the C=O bond in the initial excitation, which is also consistent with all the observations for reactions (2) and (3).


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