  Scanning tunneling microscopy with a CO-functionalized tip is combined with
simulations to explore the impact of the CO tilt angle on topographies of a
single Cu atom and CO molecule adsorbed on Cu(111). Images of the Cu atom
acquired with varying tip tilt angles and sample voltages are reproduced by the
calculations. The agreement between measured and simulated data allows to
unveil the tip-orbital composition of the tunneling current, which highlights
the role of the different $p$-orbitals of the CO-tip. Topographies of adsorbed
CO and their dependence on voltage and probe-surface distance are captured for
the nontilted junction geometry and in the limit of weak molecular
interactions.
