Energy and angular distributions of excited rhodium atoms ejected from the rhodium (100) surface

Multiphoton resonance ionization spectroscopy has been used to determine the polar-angle and the kinetic-energy distribution of Rh atoms desorbed from the ion-bombarded Rh{100} surface in the fine-structure components of the a4FJ ground-state multiplet (J=9/2 and 7/2). The overall behavior is found to be very similar to that observed for higher-lying metastable levels. The energy distribution of the metastable level (4F7/2 with excitation energy of 0.2 eV) is found to be broader than the ground-state (4F9/2) distribution. The energy distribution of the excited ejected atoms is shown to depend mainly on the electron configuration of the excited state. The measured spectra have also been used to investigate the dependence of the excitation probability on the emission velocity. It is shown that the excitation probability depends strongly on this parameter, approaching an exponential dependence on the reciprocal of the normal component of velocity at higher velocities (>5×105 cm/sec).