Knowledge Bank

{Ab initio} calculation predict that protonated methane, $CH5+$, has three low energy structures that are practically equal in energy and that barriers separating their 120 equivalent minima are $lowm$. Thus $CH5+$ provides a new prototype of spectroscopic specimen in which the five equivalent protons are attached to the central carbon $atomn$. We have observed, using our difference frequency spectrometer and the velocity modulation technique, a weak but rich spectrum of a carbocation containing one carbon. We believe they are transitions of $CH5+$ due to the formally forbidden CH stretch band based on their plasma chemical behavior and agreement with the conclusion of predissociation spectroscopy of $CH7+o$. A preliminary observational result will be reported.