15min:

EUNSOOK KIM, HIDETA HABARA AND SATOSHI YAMAMOTO, Department of Physics and Research Center for the Early Universe, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.

The 1₀₁-0₀₀ rotational transition of the ethyl radical has been detected for the first time with the Fourier transform millimeter-wave (FTMW) spectrometer. The ethyl radical is produced by discharging the C₂H₅I gas diluted in Ar. We have observed 28 paramagnetic lines in the frequency region from 43680 MHz to 43780 MHz. These lines were observed by using C₂H₅Br, CH₃CH₂COCH₂CH₃, and C₂H₆ instead of C₂H₅I, although the line intensities were weaker than the C₂H₅I case. From this evidence, we concluded that the spectral lines observed are those of C₂H₅. The lines show a very complicated pattern of the fine and hyperfine structures of the doublet radical with the nuclear spins of five protons. Therefore measurements of the Zeeman effect were useful to assign the fine and hyperfine components. As a result, the most lines were ascribed to the transitions in the A^''₂ level. The rotational constant, the spin-rotation constant, and hyperfine constants are determined by the least-squares fit.