Characteristic energy losses by slow electron impact on thin-film alkanes at 77 °K

Characteristic energy losses by slow electron impact have been measured on thin films of several alkanes at 77 °K. The cross section for the lowest loss at [inverted lazy s] 0.6 eV increases tenfold in the series n -pentane to n -nonane with increasing carbon number. For a given carbon number it decreases markedly with branching. Losses at [inverted lazy s] 3, [inverted lazy s] 6, [inverted lazy s] 9, and [inverted lazy s] 22 eV are common to all alkanes with no strong dependence on molecular size or configuration. The lowest losses may be due to temporary negative ion states or to pre-existing trapping potentials. Losses at [inverted lazy s] 3 eV may be due to the highest temporary negative ions or to triplets. If the former is correct, then [inverted lazy s] 6 eV losses can be attributed to triplets. The [inverted lazy s] 9 eV losses are due to upper singlet states, and the [inverted lazy s] 22 eV losses may be due to collective excitations.