Negative Ion Formation in N-Nonanols

Negative ion fragments from alcohols have been observed for both high energy (70 eV) and low energy (2 -20 eV) impact electrons. In the lower energy range, several resonant dissociative attachment (DA) processes have been observed. 2-propanoland five isomers of n-nonanol were examined using a modified Bendix Model 14 Time-of-Flight mass spectrometer. Modifications included changes to the electron multiplier voltages, a digital data acquistion system capable of monitoring single mass peaks, and circuits to allow repeated mass and energy scans. In 2-propanol, resonance maxima are found at 6.6, 9.5, and 11.3 eV for O('-) and at 8.6 eV for OH('-). It is shown that the 6.6 eV resonance is due to background oxygen and may be used as an energy scale calibrant. In nonanol, fragments at m/e = 1, 16, 17, and 141 were found to have resonant DA processes in all five isomers. The resonance maxima do not change with OH position. DA processes observed at m/e = 57, 71, 85, and 99 are found to correlate with OH position and may be used to identify the particular isomer under study. These resonances all occur at approximately 8.0 eV and are interpreted as having a common excited precursor state which decays through open channels determined by the OH position. For 70 eV, the mass spectra show isomeric differences in the peaks in the range m/e = 49 - 137 amu.