Poster, Highlighted on, Wednesday, September 3, 2003, 3:00-5:30pm, Sierra Ballroom I-II

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*S.T. Gibson, S.J. Cavanagh, B.R. Lewis (Australian Nat'l U.), G. Stark (Wellesely College), P.L. Smith (Harvard-Smithsonian CfA)*

Diatomic sulfur (S_{2}) has been observed in absorption, via
the strong ultraviolet B ^{3}\Sigma_{u}^{-} - X ^{3}\Sigma_{g}^{-}
system, in the atmospheres of Jupiter and Io. The
determinations of S_{2} abundances and temperatures from its
ultraviolet absorption signature are hindered by the very
large uncertainties associated with the fundamental
spectroscopic parameters of the molecule. Oscillator
strengths, line widths and line shapes are, to date, poorly
determined. As part of a combined program of calculations
and laboratory measurements, we present preliminary model
calculations of the S_{2} B - X absorption spectrum. From
limited spectroscopic information, it is known that the B
^{3}\Sigma_{u}^{-} state is heavily perturbed by
B^{\prime\prime} ^{3}\Pi_{u}, ^{1}\Pi_{u} and
^{5}\Sigma_{u}^{-}(^{5}\Pi_{u}) predissociating states (Wheeler et
al. 1998) which yield an apparently complex spectrum. In
contrast, the analogous B - X transition in molecular
oxygen (O_{2}), responsible for the Schumann-Runge bands,
has been studied extensively in the laboratory. The apparent
complexities of this spectrum are readily understood, in
terms of a coupled-channel Schrödinger equation (CSE)
model (Lewis et al. 2001). We apply a CSE model developed
for the B ^{3}\Sigma_{u}^{-} - X ^{3}\Sigma_{g}^{-} transition of
O_{2} to the analogous S_{2} spectrum, employing the
potential energy curves and coupling scheme of Wheeler et
al., as a starting point.The CSE calculations provide
valuable insight into the photodissociation spectrum,
demonstrating complex interference effects that are more
pronounced than for O_{2} and hence of significance to
planetary photochemical models. These calculations will
guide planned measurements of the strengths and lineshapes
of the B-X system. References: M. D. Wheeler, S. M.
Newman, and A. J. Orr-Ewing, J. Chem. Phys. 108, 6594-6605
(1998); B. R. Lewis, S. T. Gibson, F. T. Hawes, and L. W.
Torop, Phys. Chem. Earth (C) 26, 519-526 (2001).

The author(s) of this abstract have provided an email address for comments about the abstract: Stephen.Gibson@anu.edu.au

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Bulletin of the American Astronomical Society, **35** #4

© 2003. The American Astronomical Soceity.