Near-field time-of-flight spectroscopy of sodium atoms desorbing from surface-bound clusters.

Delayed photodesorption of Na atoms from large, surface-bound Na clusters is investigated with a novel technique that includes pulsed plasmon excitation and continuous Doppler-free two-photon evanescent wave detection of desorbing atoms. The spatial confinement of the laser beams within the evanescent wave, the Doppler-free nature of the detection mode, and an accurate evaluation of the kinetic energy of the desorbing atoms in terms of a multiphonon time-of-flight distribution allows temporal information on the decay mechanisms within the cluster to be obtained.