High-resolution and high-precision measurements of total cross section for electron scattering from CO _2

olute grand total cross section for electron scattering from CO _2 is obtained in the energy range from 20 eV down to 9 meV with a very narrow electron energy width of 11 meV using the threshold-photoelectron source employing synchrotron radiation. Although the obtained grand total cross section shows the general features of the cross-section behavior known for the low-energy electron scattering from CO _2 , namely the marked rise below 2 eV and the resonance enhancement at about 4 eV, several new features were revealed, especially at the ^2Π _u resonance. The energy position for the maxima of the grand total cross section at the ^2Π _u resonance appeared to be lower than that has been known. Also found are clear oscillatory structures resolved on the broad enhancement of the grand total cross section at around the ^2Π _u resonance. The present measurement also revealed a threshold feature due to the vibrational excitation of asymmetric stretch mode in the grand total cross section. The vibrational excitation cross section for asymmetric stretch mode at the threshold is estimated from the feature.