RESUMO
We present an experimental and theoretical investigation of the photon interaction with formic acid in the vacuum-ultraviolet energy range. The absolute absorption cross sections and ionization efficiencies were measured in the 11.2-21.4 and 13.5-21.4 eV ranges, respectively, using a double-ion chamber technique. Photoionization and neutral-decay cross sections were derived from these results. From the present ionization cross sections and previously reported ionic dissociative branching ratios, the partial cross sections for dissociating processes were obtained. Theoretically, the photoionization cross sections and the asymmetry parameters of the photoelectron angular distributions for ionization out of the six outermost valence orbitals (10a', 2aâ³, 9a', 1aâ³, 8a', and 7a') were obtained in the energy range from near-threshold to 35 eV. For that, the Padé approximant technique along with the single-center partial-wave expansion method was applied to solve the Lippmann-Schwinger equation in the static-exchange-polarization level of approximation. This is the first theoretical investigation concerning the determination of the asymmetry parameters and photoionization cross sections of formic acid in the vacuum-ultraviolet energy range. Comparison is made between our results and the previous ones.
RESUMO
In this work, we present a theoretical study on elastic electron collisions from three isoelectronic free radicals (CNN, NCN, and CCO) in the low incident energy range. More specifically, calculated differential, integral, and momentum transfer cross sections are reported in the 1-30 eV energy range. Calculations are performed in the static-exchange and static-exchange-polarization levels. The iterative Schwinger variational method is used to solve the scattering equations. Our study reveals that the calculated cross sections for the three targets are significantly different at incident energies below 10 eV. Above that energy, a remarkable similarity among the calculated results is seen.