Mean excitation energies for stopping power of atoms and molecules evaluated from oscillator-strength spectra.
The mean excitation energy for the stopping power of matter, usually expressed by symbol I, is the only nontrivial material property in Bethe's [Ann. Phys. 5, 325 (1930)] asymptotic stopping-power formula. It is therefore a crucial input for the evaluation of stopping power for swift charged particles. To calculate the I value of a material from its definition, it is necessary to know the oscillator-strength spectrum of the material in question over the entire range of the excitation energy. We evaluate the mean excitation energies of 32 atoms and molecules from the oscillator-strength spectra that were published by Berkowitz in 2002 [Atomic and Molecular Photoabsorption: Absolute Total Cross Sections (Academic, San Diego, 2002)]. We find that most of the present I values are consistent with those given in the literature. The I values of NO{sub 2}, O{sub 3}, and C{sub 60} in particular are evaluated in the present work. For buckminsterfullerene C{sub 60}, an estimation of the I value is made also using the local-plasma approximation, in an attempt at understanding differences in the I values of carbon in a free atom, a C{sub 60} molecule, and graphite. Systematic trends of I values obtained in the present calculation are discussed, in the context of the Thomas-Fermi model.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 927989
- Report Number(s):
- ANL/PHY/JA-55817
- Journal Information:
- J. Appl. Phys., Journal Name: J. Appl. Phys. Journal Issue: 6 ; Sep. 15, 2006 Vol. 100; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- ENGLISH
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