A novel model potential for modelling the environment of atoms and molecules inside fullerenes is proposed. The model takes into consideration that the electrons of the guest atom or molecule are affected by an attractive short-range Gaussian shell to simulate the C n cage. As a test case, the present model is employed to study the electronic structure of an endohedrally confined hydrogen atom by C 36 and C 60 fullerenes. This study is performed using a new implementation of the p-version of the finite-element method by a self-consistent finite-element methodology. The results are then compared with previous ones obtained by using other short-range model potentials.

An experimental photochemistry study involving gas-and solid-phase amino acids (glycine, DL-valine, DL-proline) and nucleobases (adenine and uracil) under soft X-rays was performed.The aim was to test the molecular stabilities of essential biomolecules against ionizing photon fields inside dense molecular clouds and protostellar discs analogs. In these environments, the main energy sources are the cosmic rays and soft X-rays. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing 150-eV photons. In situ sample analysis was performed by time-of-flight mass spectrometer (TOF-MS) and Fourier transform infrared (FTIR) spectrometer, for gas-and solid-phase analysis, respectively. The half-life of solid-phase amino acids, assumed to be present at grain mantles, is at least 3 × 10 5 and 3 × 10 8 yr inside dense molecular clouds and protoplanetary discs, respectively. We estimate that for gas-phase compounds these values increase 1 order of magnitude since the dissociation cross-section of glycine is lower in gas phase than in solid phase for the same photon energy. The half-life of solid-phase nucleobases is about 2-3 orders of magnitude longer than found for amino acids. The results indicate that nucleobases are much more resistant to ionizing radiation than amino acids. We consider these implications for the survival and transfer of biomolecules in space environments.

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A computational code based on the method of continued fractions, previously developed by our group for electron–molecule scattering calculations, is extended to treat photoionization of molecules of arbitrary symmetry. This new computational code is applied to study the photoionization of the two outermost valence orbitals of ammonia in the exact static-exchange level of approximation. The method has proved to be very accurate and rapidly convergent. Our results obtained for cross sections agree well with both experimental and theoretical results available in the literature.

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