Negative methane

Negative methane is the negative ion of methane, meaning that a neutral methane molecule captured an extra electron and became an ion with a total negative electric charge: CH−4. This kind of ion is also known as anion and are relevant in nature because negative ions have been observed to have important roles in several environments. For instance, they are confirmed in plasma, in the atmosphere of Earth and, in the ionosphere of Titan. Negative ions also hold the key for the radiocarbon dating method

Negative ions can not be described with conventional atomic theory. Quantum mechanical models, including more factors than solely Coulomb attraction, have to be considered to explain their stability. Such factors are Coulomb potential screening and electron correlation.

Relevance

Negative methane is important for fundamental science because methane was not expected to produce a stable negative state. It is also relevant because the existence of its negative ion demonstrates an extra property of this powerful greenhouse gas. It is also relevant for plasma science, specially for methane-based plasma. In addition, it may be important in some atmospheric environments, where there exists methane, like in the ionosphere of satellite Titan where negative ion species have been detected.