Poster II, Thursday, November 11, 2004, 4:15-7:00pm, Exhibition Hall 1A

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*J. J. Hillman (University of Maryland), W. E. Blass (University of Tennessee), D. Reuter, D. E. Jennings (NASA/GSFC)*

By combining our experimental data with the data of others,
these spectra of hydrogen and its isotopic variants will be
analyzed simultaneously to obtain a measure of the breakdown
of the Born-Oppenheimer approximation. We will employ a
variant of the Bunker-Watson extension, which accounts for
this breakdown through the nuclear mass dependence of the
Dunham coefficients. The first step in this process is to
assemble and confirm accuracy of the data set and to assign
appropriate statistical weights. Along these lines we have
combined our data with the data of others on D_{2} and
H_{2}. A total of 31 D_{2} lines and 54 H_{2} were fit to a
Dunham expansion. These data were analyzed using a modified
version of the iterative bi-weighting, stepwise regression
system. Termination of the bi-weighting iterations was
controlled by an expected-variance-driven Komolgrov-Smirnov
(K-S) test. When a maximum probability that the residuals of
the non-zero weighted observations are drawn from a normal
distribution is achieved in the bi-weighting iterations, the
process is terminated. The maximum probability is often
above 90% and the variance of the hypothetical parent
distribution is generally quite close to the expected value
for the experimental data. The D_{2} data set was fit to a
standard deviation of 0.00163 cm^{-1}, an improvement over
current literature fits. The H_{2} data were fit to a
standard deviation of 0.00458 cm^{-1}.

The ultimate goal of this research effort is to obtain a
single parameter set which can be used to calculate
vibrational-rotational energy levels for H_{2} and its
isotopic variants D_{2}, T_{2}, HD, HT and DT in the ^{1}
\Sigma ground electronic state. This analysis will
culminate in the first determination of isotopically
invariant vibration-rotation constants for the hydrogen
molecule. Such a parameter set does not presently exist to
our knowledge. Molecular hydrogen isotopes are of
fundamental importance in the molecular sciences, especially
molecular astrophysics including stellar, planetary and
galactic studies.

This effort has been partially funded by the NASA Planetary Atmospheres Program.

The author(s) of this abstract have provided an email address for comments about the abstract: jhillman@astro.umd.edu

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Bulletin of the American Astronomical Society, **36** #4

© 2004. The American Astronomical Soceity.