Observation of rotationally mediated focused inelastic resonances in D2 scattering from Cu„001..

Rotationally mediated focused inelastic resonances ~RMFIR’s! in the angular distributions of D2 scattered from Cu~001! are observed. The FIR effect involves a phonon-assisted focusing of an incident beam of arbitrary energy and direction into a final channel of one single well-defined energy and direction. Surprisingly for an incident energy Ei527 meV the RMFIR conditions for the scattered beam coincide with the kinematic conditions required for a further elastic selective adsorption mechanism called the rotationally mediated critical kinematic ~RMCK! effect. By taking advantage of the RMFIR and elastic RMCK effects, three effective bound states of energy en ,J5221.5 meV, 212.4 meV, and 210.3 meV are determined. They are attributed to the lowest bound states e05228.9 meV and e15219.8 meV combined with the rotational excitation energy for J51 to be B rotJ(J11)57.41 meV, respectively, and e35210.3 meV combined with the rotational ground state (J50). While the e1 and e3 states appear as maxima in the angular distribution at RMFIR conditions, the e0 yields a striking minimum which represents the first evidence of what we call an anti-FIR feature. Theoretical arguments to explain the different FIR signatures observed are provided. A fit of a phenomenological interaction potential to the experimental bound-state values yields a value for the well depth D532.5 meV which is somewhat deeper than that found previously. @S0163-1829~97!00839-4#