PURE ROTATIONAL SPECTRUM OF CN+

Abstract

The pure rotational spectrum of the elusive CN$^+$ cation has been observed for the first time using the cryogenic ion trap apparatus Coltrap by applying an action spectroscopy scheme. For the $^{12}$C$^{14}$N$^+$ species, the three lowest rotational transitions have been observed each of which exhibits hyperfine structure from the presence of the $^{14}$N nucleus. The rare $^{12}$C$^{15}$N$^+$ isotopolog has been studied up to the $J=4-3$ transition. The observations conclusively confirm CN$^+$ to occupy a $^1\Sigma^+$ electronic ground state. Given the ubiquity of the CN radical in space, CN$^+$ is an appealing candidate for future radio astronomical searches.