DETERMINATION OF ABSOLUTE PRODUCT BRANCHING RATIOS IN MASS-SPECTROMETRIC EXPERIMENTS - DETECTING ACETYL RADICALS AT CH2CO+

The paper describes a general method for determining absolute branchin g ratios in mass spectrometric experiments. The method overcomes the c hronic obstacle that the daughter ion fragmentation pattern of radical products is usually unknown. We report the absolute product branching ratio for competing primary C-Cl and C-C bond fission in chloroaceton e after excitation on the (1)n pi absorption band. To determine this branching ratio, acetyl chloride is used to calibrate the relative det ection efficiency of acetyl radicals at the CH2CO+ daughter ion relati ve to Cl atoms at Cl-35(+). We also calculate the daughter ion product ion probability for CH2CO+ formed from internally excited CH3CO radica ls.