We have studied the photodissociation dynamics of expansion-cooled BrO radical both above (278281.5nm) and below (355nm) the AΠ322 state threshold using velocity map ion imaging. A recently developed late-mixing flash pyrolytic reactor source was utilized to generate an intense BrO radical molecular beam. The relative electronic product branching ratios at 355nm and from 278to281.5nm were determined. We have investigated the excited state dynamics based on both the product branching and the photofragment angular distributions. We find that above the O(D21) threshold the contribution of the direct excitation to states other than the AΠ322 state and the role of curve crossing is considerably larger in BrO compared to that observed for ClO, in agreement with recent theoretical studies. The measurement of low velocity photofragments resulting from photodissociation just above the O(D21) threshold provides an accurate and direct determination of the AΠ322 state dissociation threshold of 35418±35cm1, leading to a ground state bond energy of D00(BrO)=55.9±0.1kcalmol.

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