An optogalvanic flux sensor for trace gases

We demonstrate the applicability of a new kind of gas sensor based on Rydberg excitations. From an arbitrary probe gas the molecule in question is excited to a Rydberg state, by succeeding collisions with all other gas components this molecule gets ionized and the emerging electron and ion can then be measured as a current, which is the clear signature of the presence of this particular molecule. As a first test we excite Alkali Rydberg atoms in an electrically contacted vapor cell [1,2] and demonstrate sensitivities down to 100 ppb on a background of $N_2$. We investigate different amplification circuits, ranging from solid state devices on the cell to thin film technology based transimpedance amplifiers inside the cell [3]. For a real life application, we employ our gas sensing scheme to the detection of nitric oxide in a background gas at thermal temperatures and atmospheric pressure.\\ $[1]$ D. Barredo, et al., \textit{Phys. Rev. Lett.} \textbf{110}, 123002 (2013)\\ $[2]$ R. Daschner, et al., \textit{Opt. Lett.} \textbf{37}, 2271 (2012)\\ $[3]$ J. Schmidt, et al., \textit{AMFPD} \textbf{24}, 296-298 (2017)