Author/Authors :
Linnartz، نويسنده , , H. and Motylewski، نويسنده , , T. and Maiwald، نويسنده , , F. and Roth، نويسنده , , D.A. and Lewen، نويسنده , , F. and Pak، نويسنده , , I. and Winnewisser، نويسنده , , G.، نويسنده ,
Abstract :
A Doppler-free technique for direct absorption spectroscopy of rotationally cold molecular ions in the millimeter wave range is presented. The method uses a double modulation technique, based on a simultaneous modulation of a frequency doubled microwave sweeper and a pulsed slit nozzle, incorporating a discharge in a high-pressure supersonic expansion. The performance is demonstrated with the observation of the hyperfine structure of the J=2←1 pure rotational transition of N2H+. Further perspectives of the method are discussed.
