INFRARED-SPECTROSCOPY WITH A DOUBLE MODULATION SIDE-BAND TECHNIQUE

We have applied both microwave and radio frequency modulation to CO2 laser lines using only one CdTe modulator. As a result, a grid of closely spaced (DELTA-nu almost-equal-to 1 MHz) and tunable infrared frequencies is generated. This technique was used to perform infrared-infrared double resonance experiments on the molecules 28SiH4 and 28SiF4, and to observe the Stark splitting due to extremely small dipole moments. As a preliminary result, we obtained values for several dipole moment parameters which agree with measurements performed with other techniques.