Abstract: The valence electron structure of cyclopentane was measured by using high resolution(ΔE=1.16 eV,ΔP=0.1 au) (e,2e) spectrometer.The impact energy was 1200 eV plus binding energy (i.e.1206 to 1224 eV) and a symmetric non-coplannar kinematics was employed.The measured binding energies agree with the data obtained by photoelectron spectra (PES).The experimental momentum profiles have been compared with those calculated using the Hartree-Fock method and the density function theory(DFT) method.The measured momentum distributions are consistent with the theoretical calculations.

Key words: Cyclopentane, Ionization energy, Electron momentum profiles