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Ultralong-range Cs2 Rydberg-ground molecules(nD5/2 + 6S1/2F)(33 ≤ n ≤ 39,F = 3 or 4)are investigated by a two-photon photo-association spectroscopy of an ultracold Cs gas.Two vibrational ground molecular spectra of triplet 3∑ and hyperfine mixed singlet-triplet 1,3∑ molecular states and their corresponding binding energies are attained.The experimental observations are simulated by an effective Hamiltonian including low energy electron scattering pseudopotentials,the spin-orbit interaction of the Rydberg atom,and the hyperfine interaction of the ground-state atom.The zero-energy singlet and triplet s-wave scattering lengths are extracted by comparing the experimental observations and calculations.Dependences of the measured binding energies on the effective principal quantum number,neff = n-δD(δD is the quantum defect of Rydberg D state),yield the scaling of n-5.60±0.16eff(3∑,F=3),n-5.62±0.16eff(3∑,F=4)for deep triplet potential and ne-5.65±0.38eff(1,3∑,F = 3),n-6.19±0.14eff(1,3∑,F=4)for shallow mixed singlet-triplet potential well.The simulations of low-energy Rydberg electron scattering show agreement well with the experimental measurements.