Microwave spectrum of the FCO radical in the (2)A ' electronic ground state

The 1(01)-0(00), 2(02)-1(01), and 3(03)-2(02) rotational transitions of the FCO radical are observed at 22.3, 44.5,and 66.8 GHz, respectively, using a Fourier transform millimeter-wave spectrometer with a pulsed discharge noz zle. The FCO radical is produced by discharging F2CO diluted in the Ar buff er gas. Twelve fine and hyperfine components for the three transitions are observed, and the effective rotational constant, the centrifugal distortion constant, the spin-rotation constant with its centrifugal correction term, and three hyperfine constants are determined. Furthermore, the vibrational satellites for the nu (1) = 1, nu (2) = 1, v(3) = 1, and nu (3) = 2 states are also observed in the 22.3 GHz region. From the dipolar interaction con stants, the principal axis of the dipolar interaction tenser is estimated a nd is discussed in relation to the distribution of the unpaired electron. ( C) 2001 Academic Press.