Abstract: Binding energy spectra of CF3I in the energy range 9-15 eV have been measured by a newly developed high resolution (e, 2e) spectrometer with 0.5 eV energy resolution. The two split spin-orbit components 5e3/2 and 5e1/2of the iodine lone-pair orbital have been partially resolved and their individual electron momentum distributions obtained, together with their branching ratio as a function of momentum. The experimental results clearly reveal the relativistic effects on the 5e3/2 and 5e1/2 orbital wavefunctions.