Threshold energies for production of CH 2( 3B 1) and CH 2( 1A 1) from ketene photolysis. The CH 2( 3B 1) ↔ CH 2( 1A 1) energy splitting

Abstract

By measuring the relative CO quantum yields from ketene photolysis as a function of photolysis wavelength we have determined the threshold energy at 25° for CH 2CO( 1A 1) → CH 2( 3B 1) + CO( 1Σ +) to be 75.7 ± 1.0 kcal/mole. This corresponds to a value of 90.7 ± 1.0 kcal/mole for Δ H f298 0[CH 2( 3B 1)]. By measuring the relative ratio of CH 2( 1A 1)/CH 2( 3B 1) from ketene photolysis as a function of photolysis wavelength we have determined the threshold energy at 25°C for CH 2CO( 1A 1) → CH 2( 1A 1) + CO( 1Σ +) to be 84.0 ± 0.6 kcal/mole. This corresponds to a value of 99.0 ± 0.6 kcal/mole for Δ H f298 0[CH 2( 1A 1)]. Thus a value for the CH 2( 3B 1) ↔ CH 2( 1A 1) energy splitting of 8.3 ± 1 kcal/mole is determined, which agrees with three other recent independent experimental estimates and the most recent quantum theoretical calculations.