First laboratory detection of vibration-rotation transitions of CH${}^{+}$ and ${}^{13}$CH${}^{+}$ and improved measurement of their rotational transition frequencies

The long-searched C-H stretches of the fundamental ions CH${}^{+}$ and ${}^{13}$CH${}^{+}$ have been observed for the first time in the laboratory. For this, the state-dependent attachment of He atoms to these ions at cryogenic temperatures has been exploited to obtain high-resolution rovibrational data. In addition, the lowest rotational transitions of CH${}^{+}$, ${}^{13}$CH${}^{+}$ and CD${}^{+}$ have been revisited and their rest frequency values improved substantially.