ROTATIONAL ALIGNMENT OF D-2 DESORBING FROM PD(100)

The rotational alignment of D-2 molecules desorbing from a Pd(100) single crystal surface is measured by laser-induced fluorescence via the B-1 Sigma(u)(+)<--X(1) Sigma(g)(+) Lyman bands around lambda = 106 nm and 110 nm. Different rotational states in the vibrational ground state upsilon '' = 0 are probed. For low rotational states, J '' = 2, an isotropic distribution of the J vector is found. For higher rotational states J '' greater than or equal to 3 a preference of the desorbing molecules for helicoptering over cartwheeling motion is observed, in agreement with recent theoretical predictions.