  We extend our previous shell effect observation in gold nanowires at room
temperature under ultra high vacuum to the other two noble metals: silver and
copper. Similar to gold, silver nanowires present two series of exceptionally
stable diameters related to electronic and atomic shell filling. This
observation is in concordance to what was previously found for alkali metal
nanowires. Copper however presents only electronic shell filling. Remarkably we
find that shell structure survives under ambient conditions for gold and
silver.
