The dominant contributions of the inner valence electrons to the positron annihilation process in methanol

The positron-electron annihilation gamma-ray spectra of methanol have been studied in the present work. The contributions of the bound electrons to the Doppler-shift of gamma-ray spectra have been analysed as well. These bound electrons are divided into three groups: core, inner valence and outer valence rather than the conventional two groups: core and valence in the positron annihilation process in the present work. The results obtained show a dominance of the inner valence electrons of methanol rather than the electrons occupied in the highest occupied molecular orbital (HOMO) in the positron-electron annihilation process. These inner valence electrons occupied in 3a′ and 4a′ orbitals consist of over 80% outermost atomic 2s electrons in oxygen and carbon atoms. That the positron prefers to annihilate with these outermost s electrons in atoms is suggested.