An Optogalvanic Flux Sensor for Trace Gases*

We demonstrate the applicability of a new kind of gas sensor based on Rydberg excitations. From a gas mixture the molecule in question is excited to a Rydberg state. By succeeding collisions with all other gas components this molecule becomes ionized and the emerging electron can 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 a detection limit of 100\,ppb to a background of N$_2$. We employ our gas sensing scheme to the detection of nitric oxide at thermal temperatures and atmospheric pressure [3]. We show first results of cw spectroscopy of the A$\,{}^2\Sigma^+\leftarrow\,$X$\,{}^2\Pi_{1/2}$ transition in nitric oxide. [1] D. Barredo, et al., \textit{Phys. Rev. Lett.} \textbf{110}, 123002 (2013) [2] J. Schmidt, et al., SPIE \textbf{10674} (2018) [3] J. Schmidt, et al., \textit{Appl. Phys. Lett.} \textbf{113}, 011113 (2018)