State-Resolved Energy Profiles of Transient Sulfur Monoxide Radical: Photofragments from Sulfur Dioxide UV Photodissociation*

The photodissociation dynamics from vibronically excited SO₂ (C state) molecules give insight into possible mechanisms of photochemically-induced sulfur isotope effects seen in the early earth rock record.  Photochemistry of SO₂ is investigated using tunable, pulsed UV light (λ=210-225 nm) and state-resolved high-resolution transient IR absorption spectroscopy.  Tunable UV light initiates dissociation and the photofragments are probed with 4.4 µm (2230-2300 cm^-1) light.  Individual Doppler-broadened ro-vibrational probe transitions and emission intensities were measured to determine UV-dependent dissociation quantum yields, nascent translational energy distributions, dissociation anisotropies, and rotational energy distributions.  Measurements near the photodissociation threshold shed light on the dynamics of predissociative states resulting from non-adiabatic coupling.  UV-wavelength-dependent studies of product energy partitioning were performed to characterize the dissociation mechanism from the electronically excited C state of SO₂.