  We study the pairing of fermions in a one-dimensional lattice of tunable
double-well potentials using radio-frequency spectroscopy. The spectra reveal
the coexistence of two types of atom pairs with different symmetries. Our
measurements are in excellent quantitative agreement with a theoretical model,
obtained by extending the Green's function method of Orso et al., [Phys. Rev.
Lett. 95, 060402 (2005)], to a bichromatic 1D lattice with finite harmonic
radial confinement. The predicted spectra comprise hundreds of discrete
transitions, with symmetry-dependent initial state populations and transition
strengths. Our work provides an understanding of the elementary pairing states
in a superlattice, paving the way for new studies of strongly interacting
many-body systems.
