Infrared-Microwave Double Resonance and Double Photon Transitions in FCN

Abstract

The utility of a conventional microwave spectrometer in determining the relative disposition of a CO₂ -laser line and a molecular transition and ultimately the exact frequency of an infrared transition, is demonstrated by making use of three non-linear spectroscopic effects, high frequency Stark effect, IR-MW double resonance and IR-MW double photon transitions. New situations are encountered in the production of the double photon transitions and the observation of the high frequency Stark effect. From a combination of the double photon transitions with double resonance signals produced in single d. c. Stark components it was concluded that the R (2) transition of the υ₁ band of the linear molecule FCN lies 104 ± 15 MHz lower in frequency than the R(20), 9.4 μm CO₂ -laser line i.e. R(2) transition = 1079.58711 ± 0.0005 cm^-1 .