Experimental and theoretical study of the valence electronic structure of propane by electron momentum spectroscopy

Binding energy spectra and electron momentum profiles for the valence orbitals of propane have been measured at electron impact energy of 1.2 keV plus binding energy. The experimental electron momentum profiles (XMPs) are compared with the theoretical ones calculated for the relevant molecular orbitals using density functional theory. The calculation taking molecular vibration into account can well explain high intensity of the XMPs at low momentum region for 1a(2) and 3b(2) outer valence orbitals, showing a noticeable influence of the vibrational effect on orbital electron momentum profiles. For the inner valence orbitals, an attempt to reveal the interference effect or bond oscillation has been presented through the ratios of electron momentum profiles for the bonding and anti-bonding molecular orbitals. The observation of oscillation structures indicates the presence of interference effects.