  We report on the state-selective detection of near-dissociation ultracold KRb
molecules in the ground $X^1\Sigma^+$ state and the metastable $a^3\Sigma^+$
state. The molecules are produced by photoassociation of ultracold atoms
followed by radiative decay into high vibrational levels of the $X$ and $a$
states. Detection utilizes resonance-enhanced one-color two-photon ionization,
followed by time-of-flight mass spectroscopy. Scanning the detection laser
frequency over the range 582-625 nm, we observe transitions from the
$v''$=86-92 levels of the $X$ state, which are bound by up to 30 cm$^{-1}$, and
the $v''$=17-23 levels of the $a$ state, which are also bound by up to 30
cm$^{-1}$. The measured vibrational spacings are in excellent agreement with
those previously measured and those calculated from the relevant potential
curves. Relative vibrational populations are also consistent with Franck-Condon
factors for decay from the photoassociated levels.
