Sub-doppler study of the v(3)=2 state of SF6 by infrared-infrared double resonance with a sideband spectrometer

The v(3)=2 state of SF6 has been investigated using two independently tunable sidebands of a CO2 laser. An electro-optic modulator, based an microstrip concept, is excited by a wave in the range of 0-4 GHz to create a sideband resonant with the cold band transition used as pumping radiation. A second electro-optic modulator working in the 8-18 GHz range is used to monitor the disturbance in the 2v(3)-v(3) band, About 250 lines of both the cold band v(3) and the hot band 2v(3)-v(3) have been assigned on the basis of a calculated spectrum. Their frequencies have been determined with an accuracy better than 50 kHz. The spectrum is analyzed and the lines are fitted using an effective Hamiltonian developed through the sixth order for the ground state, the seventh order for the v(3) = 1 state and the sixth order for the v(3) = 2 state. The standard deviation is a few tens of kHz for v(3) lines and a few hundreds of kHz for 2v(3)-v(3) lines. (C) 1997 American Institute of Physics.