15min:

C. A. GOTTLIEB, M. C. MCCARTHY, S. THORWIRTH AND P. THADDEUS, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A. and Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, U.S.A..

Following the initial detection of the pure sulfur clusters S₃ and S₄ at centimeter wavelengths by Fourier transform microwave spectroscopy, S₃ has subsequently been observed at millimeter wavelengths. Thirteen spectroscopic constants reproduce over 60 transitions of S₃ between 9 and 460~GHz (with J \le 87 and K_a \le 7) to within the measurement uncertainties. From these the frequencies of the astrophysically relevant lines of S₃ can be calculated to about 1~part in 10⁷ up to 500~GHz, allowing deep searches in the atmosphere of Io, dense molecular cores, and circumstellar shells of late-type stars with existing millimeter- and submillimeter-wave telescopes.