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 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 \textbf{[1,2]} and demonstrate a detection limit of 100 ppb to a background of N$_{\mathrm{2}}$. For a real life application, we employ our gas sensing scheme to the detection of nitric oxide at thermal temperatures and atmospheric pressure \textbf{[3].} We are planning to reduce the detection limit to 1 ppb using state of the art cw lasers for the Rydberg excitation of NO. This is a competitive value for applications in breath analysis and environmental sensing. [1] D. Barredo, et al., \textit{Phys. Rev. Lett.} \textbf{110}, 123002 (2013) [2] J. Schmidt, et al., \textit{SPIE} \textbf{10674} (2018) [3] J. Schmidt, et al., \textit{Appl. Phys. Lett.} \textbf{113}, 011113 (2018)