TITLE

Absolute transition probability measurement of valence-shell electronic structure of CF4 and CCl4: Bethe surfaces, and dipole-dominated preionization-edge valence and Rydberg states

AUTHOR(S)
Ying, J. F.; Leung, K. T.
PUB. DATE
May 1994
SOURCE
Journal of Chemical Physics;5/15/1994, Vol. 100 Issue 10, p7120
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Absolute generalized transition probabilities or generalized oscillator strengths (GOSs) of valence-shell electronic transitions of CF4 and CCl4 have been determined as functions of energy loss and momentum transfer (i.e., the Bethe surfaces) using angle-resolved electron energy loss spectroscopy (EELS) at an impact energy of 2.5 keV. A low-lying feature at 7.2 eV was observed for CCl4 and was attributed predominantly to electronic transitions from the Cl 3p nonbonding orbitals (2t1, 7t2, and 2e) to a C–Cl σ* antibonding orbital (7a1), based on the result of a single-excitation configuration interaction excited-state calculation. The experimental GOS profile of this low-lying feature was found to have a shape characteristic of a mixture of dipole-allowed and nondipole transitions with relative maxima at momentum transfers of 0 and ∼0.9 a.u., respectively. GOS profiles of other low-lying discrete transitions below the first ionization edge at 12.6 and 13.7 eV in CF4 and at 8.7 and 9.7 eV in CCl4 were also determined and found to have secondary minima and maxima, in addition to the strong maximum at zero momentum transfer. These excitation features were assigned mainly to Rydberg transitions originated from the nonbonding highest occupied molecular orbitals (HOMOs) with t1 symmetry and the second HOMOs with t2 symmetry. The extrema in the GOS profiles have been discussed by considering the spatial overlap of the initial-state and final-state orbital wave functions. Tentative assignments for the rest of the valence-shell energy-loss features of CF4 (5–200 eV) and CCl4 (5–150 eV) were also inferred from the term values reported previously.
ACCESSION #
7643899

 

Related Articles

Share

Read the Article

Courtesy of VIRGINIA BEACH PUBLIC LIBRARY AND SYSTEM

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics