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Updated: May 3, 2026

Molecular Beam Mass Spectrometry With Tunable Vacuum Ultraviolet VUV Synchrotron Radiation
Published on: October 30, 2012
Shape resonance spectra of uracil, 5-fluorouracil, and 5-chlorouracil
F Kossoski1, M H F Bettega2, M T do N Varella1
1Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, São Paulo, Brazil.
Abstract:
We report on the shape resonance spectra of uracil, 5-fluorouracil, and 5-chlorouracil, as obtained from fixed-nuclei elastic scattering calculations performed with the Schwinger multichannel method with pseudopotentials. Our results are in good agreement with the available electron transmission spectroscopy data, and support the existence of three π∗ resonances in uracil and 5-fluorouracil. As expected, the anion states are more stable in the substituted molecules than in uracil. Since the stabilization is stronger in 5-chlorouracil, the lowest π∗ resonance in this system becomes a bound anion state. The present results also support the existence of a low-lying σCCl (*) shape resonance in 5-chlorouracil. Exploratory calculations performed at selected C-Cl bond lengths suggest that the σCCl (*) resonance could couple to the two lowest π∗ states, giving rise to a very rich dissociation dynamics. These facts would be compatible with the complex branching of the dissociative electron attachment cross sections, even though we cannot discuss any details of the vibration dynamics based only on the present fixed-nuclei results.
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