  We report the first measurement of the odd-isotope fractions for barium,
\fodd\, in two extremely metal-poor stars: a CEMP-r/s star \he\
(\feh\,$=-2.42\pm0.11$) and an r-II star \cs\ (\feh\,$=-2.90\pm0.13$). The
measured \fodd\ values are $0.23\pm0.12$ corresponding to $34.3\pm34.3$\% of
the r-process contributions for \he\ and $0.43\pm0.09$ corresponding to
$91.4\pm25.7$\% of the r-process contribution to Ba production for \cs. The
high r-process signature of barium in \cs\ ($91.4\pm25.7\%$) suggests that the
majority of the heavy elements in this star were synthesised via an r-process
path, while the lower r-process value ($34.3\pm34.3\%$) found in \he\ indicates
that the heavy elements in this star formed through a mix of s-process and
r-process synthesis. These conclusions are consistent with studies based on AGB
model calculations to fit their abundance distributions.

Solar and Stellar Astrophysics