  The local interaction of charges and light in organic solids is the basis of
distinct and fundamental effects. We here observe, at the single molecule
scale, how a focused laser beam can locally shift by hundreds-time their
natural linewidth and in a persistent way the transition frequency of organic
chromophores, cooled at liquid helium temperatures in different host matrices.
Supported by quantum chemistry calculations, the results are interpreted as
effects of a photo-ionization cascade, leading to a stable electric field,
which Stark-shifts the molecular electronic levels. The experimental method is
then applied to a common challenge in quantum photonics, i.e. the independent
tuning and synchronization of close-by quantum emitters, which is desirable for
multi-photon experiments. Five molecules that are spatially separated by about
50 microns and originally 20 GHz apart are brought into resonance within twice
their linewidth. Combining this ability with an emission linewidth that is only
limited by the spontaneous decay, the system enables fabrication-free,
independent tuning of multiple molecules integrated on the same photonic chip.
