Infrared (ir) radio-frequency (rf) double-resonance spectroscopy was carried out on the vibrational-overtone band of methyl iodide molecules (CH<sub>3</sub>I). An optical Fabry-Perot cavity was employed as an absorption cell to record saturated ir spectral lines even by a small-power extended-cavity diode laser with a high sensitivity and a wide tunability in the presence of a rf field. These features allowed investigation of molecules strongly coupled with monochromatic and bichromatic rf fields, or dressed molecules, at various rf power levels and detuning frequencies for a variety of ir and rf transitions. At appropriate energy-level schemes, quantum-interference effects were observed. All resultant spectra showed good agreement with dressed-state theoretical calculations, indicating that the present spectrometer is valid for precise investigation of dressed molecules.
© 2001 Optical Society of America
(020.1670) Atomic and molecular physics : Coherent optical effects
(020.3690) Atomic and molecular physics : Line shapes and shifts
(300.6320) Spectroscopy : Spectroscopy, high-resolution
(300.6410) Spectroscopy : Spectroscopy, multiphoton
(300.6460) Spectroscopy : Spectroscopy, saturation
Chikako Ishibashi, Ryuji Saneto, and Hiroyuki Sasada, "Infrared radio-frequency double-resonance spectroscopy of molecular vibrational-overtone bands using a Fabry–Perot cavity-absorption cell," J. Opt. Soc. Am. B 18, 1019-1030 (2001)