Interference Effects on ($e$, $2e$) Electron Momentum Profiles of ${\mathrm{CF}}_4$

Interference effects on electron momentum profiles have been studied using binary ($e$, $2e$) spectroscopy for the three outermost molecular orbitals of ${\mathrm{CF}}_4$, which are composed of the F $2p$ nonbonding atomic orbitals. An analysis of the measured spherically averaged electron momentum densities has clearly shown the presence of oscillatory structures having direct information about the internuclear distance between the F atoms. Furthermore, it is demonstrated that the phase of the oscillatory structures depends upon the orientation in space of the constituent atomic orbitals.

Figure 1

Binding energy spectra of ${\mathrm{CF}}_4$ measured at an azimuthal angle difference $\Delta \varphi =0.5°$ and at $E_0=$ (a) 2.0 and (b) 1.6 keV. Vertical bars indicate the ionization energies of the outer valence orbitals. The broken curves represent the Gaussian deconvolution functions of the data and the solid curve their sum.

Figure 2

(a) Comparison of experimental and theoretical momentum profiles for the sum of contributions from the three outermost molecular orbitals of ${\mathrm{CF}}_4$ measured at $E_0=2.0\mathrm{keV}$. (b) Experimental bond oscillation for the three outermost molecular orbitals. The chain and solid lines represent results of a least-squares fit to the experiment and the associated DFT calculation, respectively.

Figure 3

Comparison of experimental and DFT bond oscillations for the (a) $1t_1$, (b) $4t_2$, and (c) $1e$ molecular orbitals of ${\mathrm{CF}}_4$ measured at $E_0=1.6\mathrm{keV}$. The inserted figures are the corresponding theoretical electron density distributions in $r$ space.