Broadband and low insertion loss Stark cell for microwave spectroscopy

A groove guide cell for Stark modulation spectroscopy has been constructed and tested. This structure with quasi‐unique mode propagation between two isolated plates is well adaped to application of a modulation voltage. The insertion losses are low (0.6 dB for a 3‐m‐long cell, and R band) and the cell is free of internal reflection. A metallic casing inclosing the plates acts as a shield against electrical interference, prevents low‐voltage breakdown, and reduces wall adsorption of the gas. The performance of the cell is not affected by temperature variation (−80 ° to 25 °C). A high sensitivity has been obtained by converting the cell into a 3‐m‐long, high‐Q cavity. This type of cell appears to particularly recommend itself for use in intensity measurements, broadband spectroscopy, analytical studies, and high frequency range work.