Adsorption studies of CO 2 on Cu(110) at low temperatures (45 K -120 K) have shown no detectable CO or adsorbed oxygen species using high-resolution energy electron loss spectroscopy (HREELS) and AES, indicating that CO 2 does not undergo chemisorption on low-index plane surfaces of copper. Based on temperature programmed desorption measurements after the exposure of a clean Cu(110) surface to CO 2 (leaked into the UHV chamber, 300 K, dose = 4 Langmuir(L)), Fu and Samorjai reported that no dissociation could be observed. However, under similar conditions, they also reported that CO 2 readily dissociates on stepped Cu(311) and Cu(332) surfaces, forming CO and adsorbed oxygen at a dose of 4L and surface temperature of 150 K. These observations are consistent with the fact that the dissociation of CO 2 on low-index planes of copper surfaces has a much higher activation barrier when compared to stepped surfaces. Molecular beam surface scattering experiments are well-suited to study such high-barrier dissociation processes. Here the incidence energy of the molecular beam can be precisely controlled and the S 0 along with its incidence energy dependence can be studied to understand the characteristics of the reaction pathway. Interestingly, Funk and co-workers using molecular beam methods have reported no evidence of dissociation of CO 2 on Cu(110) within their detection limit (S 0 = 0.03) even with high incidence translation energies (E i ) ranging up to 1.3 eV. This is indeed surprising as the experimentally estimated dissociation barrier was much lower at 0.64 eV. Our previous work using molecular beam-surface scattering resolves this apparent inconsistency revealing that the S 0 ranges from 3.9 × 10 -4 to 1.8 × 10 -2 within the E i range of 0.64 eV to 1.59 eV. We also found that the S 0 at E i = 1.59 eV, nearly the limit of what can be obtained using a room temperature nozzle, showed a strongly increasing trend with E i , suggesting that it is still far from reaching its maximum value. Assuming a 1-dimensional (1D) potential energy surface (PES) and based on extrapolating the observed trend in the E i dependence of S 0 , the activation barrier was estimated to be of the order of 2 eV. Interestingly, recent theoretical work on the same system, based on dynamical calculations on a high-dimensional PES, suggests that CO 2 dissociation on Cu(110) occurs via a much more complex pathway (compared to a simple 1D picture) involving multiple barriers and in an indirect manner. The activation barrier was estimated to be of the order of 0.6 eV, consistent with several previous studies, but is in contrast to the conclusions from our recent molecular beam-based studies. Low values of the S 0 , even at E i much larger than the estimated barrier height, were attributed to the fact that the reaction pathway is highly constrained, leading to only a small fraction of the incident molecules to dissociate.