Chemistry, Gas Lasers And The Co2

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Both physicists and chemists have investigated the CO2 anion extensively over the past few decades because of its importance in atmospheric chemistry, gas lasers, and a multitude of different industrial applications. It has been observed in a variety of experimental processes such as electron collisions and high-energy applications. As is well-known, electrons cannot permanently attach to the CO2 molecule; as such, all CO¬2 anion states are inherently metastable and have finite lifetimes. Despite the many studies, both experimental and theoretical, there are still a number of unanswered questions, especially concerning the relationship between short-lived and long-lived temporary anion states. Direct electron attachment to the CO2 molecule produces only short-lived anion states with lifetimes in the femtosecond range. These short- lived species consist most importantly of the low lying anionic states 2Πu and 2Σg+ 1–6. They are the main contributor to the electron scattering from neutral CO2. The 2Σg+ virtual state is responsible for the zero-energy peak in scattering experiments with energies for electron scattering below 1eV, while the 2Πu resonance state can be attributed to the observed peak in scattering cross sections at about 3.8eV. Long-lived CO2 anion states on the other hand, have been observed with lifetimes in the microsecond, even millisecond range7,8. They can be produced in processes such as double electron attachment to CO2+ ions9,10, sputtering techniques11,
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