title: Vibronic effects on the low-lying electronic excitations in CO2 induced by electron impact.
abstract: We report an angle-resolved electron energy loss spectroscopy (EELS) study on the valence-shell electronic excitations of CO2. Experimentally, momentum-transfer-dependent generalized oscillator strengths (GOSs) or GOS profiles for low-lying electronic excitations have been derived from EELS spectra measured at incident electron energy of 3 keV. Theoretically, we have calculated GOS profiles using wave functions at the equation-of-motion coupled-cluster singles and doubles level. In the calculation, vibronic effects are taken into account by evaluating the electronic transition amplitudes along the individual normal coordinates. The calculation satisfactorily reproduces the experiment for the (1)Πg and (1)Δu transitions and reveals prominent roles of strong coupling between the associated mixed-Rydberg-valence and valence excited states through the bending vibration of CO2. Vibronic effects on GOS profiles have also been examined for the (1)Σu (+), (1)Πu, and 2(1)Πg transitions.
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan. noboru@tagen.tohoku.ac.jp
authors.forename: Noboru
authors.initials: N
authors.lastname: Watanabe
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Hirayama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Suzuki
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takahashi
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D004583:Electrons; D046590:Spectroscopy, Electron Energy-Loss
chemical_list: D002245:Carbon Dioxide