The relationship between the inner-shell electron energy-loss spectra and the 29Si NMR spectra of the chlorosilanes, SiHxCl4−x. An interpretation of the trend in NMR shieldings

1994 ◽  
Vol 219 (1-2) ◽  
pp. 65-74 ◽  
Author(s):  
J.A. Tossell
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Nmr Spectra ◽  
29Si Nmr ◽  
Shell Electron ◽  
29Si Nmr Spectra ◽  
Electron Energy Loss ◽  
The Relationship ◽  
Electron Energy Loss Spectra

scholarly journals The σ* molecular orbitals of perfluoroalkanes as studied by inner-shell electron energy loss and electron transmission spectroscopies

1988 ◽  
Vol 66 (8) ◽  
pp. 2104-2121 ◽  
Author(s):  
I. Ishii ◽  
R. McLaren ◽  
A. P. Hitchcock ◽  
K. D. Jordan ◽  
Y. Choi ◽  
...  
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Inductive Effect ◽  
Oscillator Strengths ◽  
Negative Ion ◽  
Electron Transmission ◽  
Ultraviolet Excitation ◽  
Shell Electron ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Absolute oscillator strength spectra in the C 1s (280–340 eV) and F 1s (680–740 eV) regions of the perfluoro-n-alkanes from C2 to C6 and perfluorocycloalkanes from C3 to C6 have been determined from inner-shell electron energy loss spectra recorded under electric-dipole scattering conditions. The spectral features are interpreted in terms of spatially localized transitions terminating at orbitals of predominantly σ*(C—F) and σ*(C—C) character. When compared to the spectra of the perfluoro-n-alkanes, both the C 1s and F 1s spectra of the perfluorocycloalkanes exhibit additional low-lying bands which are assigned to transitions terminating at σ*(C—C) orbitals which are shifted to low energy by the combination of the strain of cyclization and the inductive effect of the fluorination. The electron transmission spectra of selected perfluorocycloalkanes (which provide information on their anion states) show as well that the electron affinities of the cyclic systems are substantially lower than those of the corresponding perfluoro-n-alkanes, again as a result of a low-lying σ* orbital in the cyclic species. Quantum chemical calculations of the alkane and perfluoroalkane ground-state orbital structures support the experimental results. The localized character of the inner-shell excitations, indicated by the constancy of both term values and oscillator strengths with increasing chain length, contrasts with the more delocalized character of the states accessed in ultraviolet excitation or negative ion formation.

Sign in / Sign up

Export Citation Format

Share Document