  We present preliminary results on the calculation of synthetic spectra
obtained with the stellar model atmospheres developed by Cardona, Crivellari,
and Simonneau. These new models have been used as input within the SYNTHE
series of codes developed by Kurucz. As a first step we have tested if SYNTHE
is able to handle these models which go down to log tau(Ross)= -13. We have
successfully calculated a synthetic solar spectrum in the wavelength region
2000--4500 A at high resolution (R=522,000). Within this initial test we have
found that layers at optical depths with log tau(Ross) < -7 significantly
affect the mid-UV properties of a synthetic spectrum computed from a solar
model. We anticipate that these new extended models will be a valuable tool for
the analysis of UV stellar light arising from the outermost layers of the
atmospheres.
