  We have mechanically fabricated a Pd nanowire in solution under
electrochemical potential control. A clear feature appeared in the conductance
histogram when the electrochemical potential of the Pd wire was kept at the
hydrogen evolution potential. Conductance traces showed the Pd wire was
stretched 0.4 nm in length just before breaking, suggesting that at least two
Pd atoms might contribute to the formation of the Pd wire. The results indicate
that a certain atomic configuration of the Pd nanowire is stabilized by
hydrogen. We discuss the stabilization mechanism due to changes in bond
strengths caused by hydrogen adsorption or incorporation.
