The first experimental observations to our knowledge of sub-Doppler linewidths in a cell made using tunable far-infrared radiation are reported. A double-resonance scheme has been used, combining CO2-laser infrared radiation with tunable far-infrared radiation to observe a sub-Doppler line shape in an excited vibrational state of CH3OH.
Sub-Doppler tunable far-infrared spectroscopy / M. Inguscio;L. R. Zink;K. M. Evenson;D. A. Jennings. - In: OPTICS LETTERS. - ISSN 0146-9592. - STAMPA. - 12:(1987), pp. 867-869. [10.1364/OL.12.000867]