We have used high resolution transmission electron microscopy to determine the structure of gold nanowires generated by mechanical stretching. Just before rupture, the contacts adopt only three possible atomic configurations, whose occurrence probabilities and quantized conductance were subsequently estimated. These predictions have shown a remarkable agreement with conductance measurements from a break junction operating in ultrahigh vacuum, corroborating the derived correlation between nanowire atomic structure and conductance behavior.

We present a joint theoretical and experimental investigation of the absorption spectra of silver clusters Ag n ͑4 Յ n Յ 22͒. The experimental spectra of clusters isolated in an Ar matrix are compared with the calculated ones in the framework of the time-dependent density functional theory. The analysis of the molecular transitions indicates that the s-electrons are responsible for the optical response of small clusters ͑n Յ 8͒ while the d-electrons play a crucial role in the optical excitations for larger n values.

We present an in situ and time resolved high-resolution transmission electron microscopy study of the atomistic process during the last elongation stages of gold nanojunctions. In particular, we concentrate on suspended chains of atoms, which have shown to be remarkably stable, although they present rather long bonds ͑3.0-3.6 Å͒. One-atom-thick junctions are robust, but their attachment points move rather easily on the metal surface, allowing the accommodation of apex movements or rotations.