We have measured the survival probability of H2 in a single rovibrational state (v = 1, 1 = 1) scattering from a Cu(110) surface at 78 meV translational energy, using molecular beam and laser state preparation techniques.The integrated survival probability is found to be only 0.74~0.13, compared with 1.00 for the (v = O, J = 1) state. Possible loss channels for the vibrationally excited H2, including dissociation and inelastic scattering, are discussed. PACS numbers: 82.65.Pa, 34.50.Lf, 34.50.Pi, 68.35.Ja The hydrogen/copper system has become a prototype for studying activated dissociative adsorption for both experiment and theory [1,2]. On the experimental side, molecular beam studies of adsorption [3 -6] and laserbased studies of desorption [7,8] have gone a long way towards characterizing general trends in the translational, rotational, and vibrational state dependence of adsorption and desorption. On the theoretical side, advances have been equally impressive, with multidimensional first-principles potential energy surfaces being published [9 -12] and dynamical calculations on these surfaces verifying qualitatively the experimental trends. The dissociative adsorption of H2 on copper is thought to be dominated by vibrationally excited molecules at low ((0.4 eV) incident translational energy [1,2,4]. To explore this possibility, scattering experiments in which the translational and vibrational degrees of freedom of the molecule are controlled independently are needed. These results provide an important test of models for activated sticking and mode-specific surface dynamics.Several groups have used seeded molecular beams generated with heated nozzles to gain partially independent control over the translational and internal (rovibrational) excitation of the incident molecules [4,6]. Their studies demonstrated that internal excitation can be effective in overcoming the barrier to dissociative adsorption. In these studies, however, the incident molecules have thermal distributions of rovibrational states; this complicates interpretation of the results for individual states. Hodgson, Moryl, and Zhao [5] performed a heated nozzle experiment using laser-ionization detection to measure the survival probability of a selected rovibrational state.Again, however, a thermal distribution is present in their incident beam. In addition, they scale their measured reAectivity to the scattered ground state intensity to avoid integrating over the scattering angle.Here we present the first results of our scattering experiment using both laser state preparation and detection to gain true quantum state specificity. We report a measurement of the survival probability of H2 (v = 1, 1 = 1) scattered from Cu (110) at low incident translational energy (78 meV). Our measurement is absolute in that we have integrated the incident and scattered signal over 16 cm Cho Pulsed Nozzle Skl pie Probe Laser Beam mp Laser am ector Assembly FIG. 1. Schematic diagram of the experiment. A pulsed supersonic beam of Hq is incident normally on a Cu(11...