HIGH-RESOLUTION ROTATIONAL SPECTROSCOPY OF CH3I USING A NOVEL DOPPLER-FREE TECHNIQUE

A new experimental approach to double resonance spectroscopy is discus sed in detail. The method uses collinear propagation of radiation of t wo frequencies to achieve velocity selection; it does not rely on nonl inear effects and it has a great sensitivity. Some examples of its app lication to the infrared-microwave region are described. By using a CO 2 laser and a mm-wave klystron we measured the frequency of rotational and vibrational transitions of CH3I with sub-Doppler resolution. We a lso obtained the first measurement of the electric dipole moment in th e v(6) = 1 excited vibrational state acid result is mu(6) = 1.6295(6) D. (C) 1996 Academic Press, Inc.