Beam Maser Spectroscopy of Rotational Transitions below One Megahertz

Abstract

Low frequency rotational transitions of formaldehyde molecule, 3₃₀→3₃₁, 7₄₃→7₄₄ and 10₄₆→10₄₇, were observed by a beam type maser spectrometer. The observed freqencies are 656.2±0.5 kHz, 819.5±0.5 kHz, and 14846±1 kHz, respectively. Except the frequency of the J=3, K₋₁=3 line, they nearly agree with the values calculated from molecular constants which have been obtained from microwave spectroscopy. A possible mechanisms for the frequency difference between the observed and calculated values is discussed.
Stark effect of the J=3, K₋₁=3, line was studied. The saturation in emission line with an increase of the focuser voltage was remarkable in the J=3, K₋₁=3 line. The saturation effect of this line is compared with those of the J=4, K₋₁=3 and the J=5, K₋₁=3 lines. They are consistent with each other.