Quantum yields for product formation in the 120-133 nm photodissociation of O₂

The photodissociation of O₂ in the region from 120-133 nm has been investigated using product imaging. The spectrum in this region is dominated by transitions from the ground state to the first three vibrational levels of the E³∑_u^- state. The O( ¹D) + O(³P) channel is the only product channel observed by product imaging for dissociation at either 124.4 nm or 120.4 nm. The O( ¹D₂) product is aligned in the molecular frame in such a way that its J vector is perpendicular to the relative velocity vector between the O(¹D) and the O(³P). The variation in the anisotropy of dissociation is approximately predicted by considering transitions on individual lines and then taking into account the coherent excitation of overlapping resonances. At 132.7 nm, both the O(¹D) + O( ³P) and the O(³P) + O(³P) channels are observed with branching ratios of 0.40±0.08 and 0.60±0.09, respectively. At 130.2 nm, the quantum yield for production of O(¹D) is 0.76±0.28.