Knowledge Bank

It will be shown that the radiation power change and radiation field change associated with a gas-phase microwave spectroscopic transition differ. (1) The power change approaches a constant as power saturation increase while the field change approaches zero. (2) The power change is proportional to the rate of approach to equilibrium of the saturated system while the field change is proportional to the ratio of the rate of approach to equilibrium to the rate at which the line is broadened. Utilizing the above information, comments on the sensitivity of a conventional stark-modulated, microwave spectrometer will also be included. It will be shown that the intensity coefficient is not a good measure of sensitivity as the same intensity coefficient for different molecules can produce greatly different signals even if the power in the absorption cell is kept constant.