Magnetic Susceptibility of Sr$\text{}_{2}$CuO$\text{}_{3}$ and SrCu$\text{}_{2}$O$\text{}_{3}$

The observed magnetic susceptibility χ$\text{}^{obs}$(T) data of Ami et al. for the linear-chain cuprate Sr$\text{}_{2}$CuO$\text{}_{3}$ are re-analyzed in terms of recent theory of Eggert et al. for the spin susceptibility χ(T) of the spin S=1/2 linear-chain Heisenberg antiferromagnet, which yielded the Cu-Cu exchange constant J/k$\text{}_{B}$=2150 K. Values for J', the exchange constant in the rungs, and J, that in the legs, were estimated for the S=1/2 two-leg ladder compound SrCu$\text{}_{2}$O$\text{}_{3}$, using the χ(T) data of Azuma et al. The analyses suggest that J'/J ≈ 0.5, contrary to the expectation that J'/J ≈ 1, and that J/k$\text{}_{B}$ is very large ( ≈ 2000 K), similar to that in Sr$\text{}_{2}$CuO$\text{}_{3}$.