  Notwithstanding the discreteness of metallic constrictions, it is shown that
the finite elasticity of stable, single-atom gold constrictions allows for a
continuous and reversible change in conductance, thereby enabling observation
of channel saturation and conductance quantization. The observed channel
saturation and signature for conductance quantization is achieved by
superposition of atomic/subatomic-scale oscillations on a
retracting/approaching gold tip against a gold substrate of a scanning probe.
Results also show that conductance histograms are neither suitable for
evaluating the stability of atomic configurations through peak positions or
peak height nor appropriate for assessing conductance quantization. A large
number of atomic configurations with similar conductance values give rise to
peaks in the conductance histogram. The positions of the peaks and counts at
each peak can be varied by changing the conditions under which the histograms
are made. Histogram counts below 1Go cannot necessarily be assumed to arise
from single-atom constrictions.
