Rydberg state photochemistry of 1,4-diazabicyclo[2.2.2]octane excited by 193- and 248-nm lasers

Article abstract of DOI:10.1021/j100295a020

Linear and nonlinear photochemistries of 1,4-diazabicyclo[2.2.2]octane (DABCO) are investigated at room temperature by using ArF (193 nm) and KrF (248 nm) lasers. With an unfocused beam geometry, DABCO vapor displays a strong fluorescence when excited at 248 nm, but it shows no detectable emission with 193-nm excitation. The linear photochemistry quantum yield for DABCO is determined as φ_P(248 nm) ? 0.1 and φ_P(193 nm) ? 0.3. The main stable photochemical products are analyzed as C₂H₄ and C₂H₂ for 248- and 193-nm excitation, respectively. When focused beam excitation is used, both ArF and KrF lasers dissociate DABCO molecules and give three strong radical emissions of CN*(B²Σ⁺→X ²Σ⁺), CH*(A²Δ→X²Π), and C₂*(d³Π_g→a ³Π_u). The time behavior, the laser power dependence, and the sample pressure dependence of these emissive radicals are examined. The possible mechanisms for the Rydberg state photochemistry of DABCO are discussed.