  Photoexcitation rates for creation of ultralong-range Rydberg molecules
(ULRM) with 31$\lesssim n \lesssim41$ in both ground and excited vibrational
levels in cold ($T\sim900$~nK) gases of polarized and unpolarized $^{87}$Sr are
presented. The measured production rates of the $\nu=0, 1$ and 2 vibrational
levels reveal rather different $n$ dependences which are analyzed by evaluating
the Franck-Condon factors associated with excitation of the different
vibrational levels and molecular rotational states. In particular, for gases of
spin-polarized fermions, only Rydberg dimers with odd rotational quantum
numbers are excited due to the requirement that their wavefunctions be
anti-symmetric with respect to exchange. The data also demonstrate that
measurements of the formation of vibrationally-excited $\nu=1$ molecules can
furnish a probe of pair correlations over intermediate length scales extending
from $\sim20$~nm to greater than 250~nm.
