Some Devices for the Stark Modulation Millimeter-Wave Spectrograph

Abstract

High sensitivity and wide‐band frequency characteristic for a microwave spectrograph are required for the detection of weak absorption lines and for researches on the hyperfine structures of the spectral lines of free molecules in the millimeter wave range. In order to improve the important components of spectrograph, the author has designed a low‐loss K‐band Stark cell, a frequency multiplier of wide‐band frequency character, a Wheatstone bridge‐type triode lock‐in detector and a compact square wave generator. The overall sensitivity of the spectrograph using these elements was about 5×10⁻⁸ cm⁻¹ in the 6 mm wave range. Thus, the author has succeeded in detecting new spectral lines [J. Phys. Soc. Japan 9, 135 (1954)] of CH₂O and in observing their new magnetic hyperfine structures (to be published).