15min:

M. C. MCCARTHY AND P. THADDEUS, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; LEVENT SARI AND HENRY F. SCHAEFER III, Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2525; ZHENHONG YU, Department of Chemistry, Harvard University, Cambridge, MA 02138.

The rotational spectrum of a novel monobridged isomer of Si₂H₄, denoted here as H₂SiHSiH, has been detected by means of Fourier transform microwave spectroscopy in a supersonic molecular beam through the discharge products of silane. On the basis of high-level coupled cluster theory, this isomer is calculated to lie only 7~kcal/mol above disilene (H₂SiSiH₂), the most stable isomeric arrangement of Si₂H₄, and to be fairly polar, with a calculated dipole moment of µ=1.14~D. The rotational spectrum of H₂SiHSiH exhibits closely-spaced line doubling, characteristic of a molecule undergoing high-frequency inversion motion; at the CCSD(T) level of theory the barrier height to inversion is calculated to be 10-11~kcal/mol. Because of its favorable energetics and high polarity with respect to either disilene or silylsilylene, monobridged Si₂H₄ is a good candidate for radioastronomical detection in sources such as IRC+10216 where other large silicon-bearing molecules have already been discovered.