Generation of (M-H)− ions by dissociative electron attachment to simple organic acids M

Low energy (∼0-3.5 eV) dissociative electron attachment to the simplest organic acids (formic, acetic and propanoic) is studied at high electron energy resolution (60 meV) by means of mass spectrometric detection of the product anions. For all (M-H)− negative fragment ions produced, vibrational structure in the attachment spectra is observed. The energy gaps between the vibrational levels in HCOO−, CH3COO− and CH3CH2COO− are derived (ranging from 250±60 meV up to 350±60 meV).