High-resolution carbon 1s photoelectron spectroscopy of propyne (HC
![](/images/entities/tb<font color=)
d1.gif">CCH
3) shows a spectrumin which the contributions from the three chemically inequivalent carbons are clearly resolve
d an
d marke
d by
distinct vibrational structure. This structure is well accounte
d for by ab initio theory. For 3,3,3-trifluoropropyne(HC
![](/images/entities/tb<font color=)
d1.gif">CCF
3) an
d ethynylsulfur pentafluori
de (HC
![](/images/entities/tb<font color=)
d1.gif">CSF
5), the ethynyl carbons show only a broa
d structurean
d have energies that
differ only slightly from one another. The core-ionization energies can be qualitativelyun
derstoo
d in terms of conventional resonance structures; the vibrational broa
dening for the fluorinate
dcompoun
ds can be un
derstoo
d in terms of the effects of the electronegative fluorines on the charge
distribution.Combining the experimental results with gas-phase aci
dities an
d with ab initio calculations provi
des insightsinto the effects of initial-state charge
distribution an
d final-state charge re
distribution on ionization energiesan
d aci
dities. In particular, these consi
derations make it possible to un
derstan
d the apparent para
dox that SF
5an
d CF
3 have much larger electronegativity effects on aci
dity than they have on carbon 1s ionization energies.