Rotational effects on vibrational excitation of H-2 on Cu(100)

Previous experiments have shown that vibrational excitation of H-2 on Cu(11 1) is accompanied by rotational cooling but were unable to resolve the unde rlying mechanism. Six-dimensional quantum dynamical calculations on scatter ing of (v = 0,j) H-2 from Cu(100) strongly suggest that the observed coolin g is due to rotational deexcitation occurring simultaneously with vibration al excitation. An alternative mechanism, in which vibrational excitation de creases with increasing initial angular momentum j but j itself is conserve d, is ruled out with certainty. [S0031-9007(99)08471-9].