  We investigate the coupling of a single molecule to a single spherical gold
nanoparticle acting as a nano-antenna. Using scanning probe technology, we
position the particle in front of the molecule with nanometer accuracy and
measure a strong enhancement of more than 20 times in the fluorescence
intensity simultaneous to a 20-fold shortening of the excited state lifetime.
Direct comparison with three-dimensional calculations allow us to decipher the
contributions of the excitation enhancement, spontaneous emission modification,
and quenching. Furthermore, we provide direct evidence for the role of the
particle plasmon resonance in the modification of the molecular emission.
