  Liquid argon is an excellent medium for detecting particles, given its yields
and transport properties of light and charge. The technology of liquid argon
time projection chambers has reached its full maturity after four decades of
continuous developments and is, or will be, used in world class experiments for
neutrino and dark matter searches. The collection of ionization charge in these
detectors allows to perform a complete tridimensional reconstruction of the
tracks of charged particles, calorimetric measurements, particle
identification. This work proposes a novel approach to the problem of charge
recombination in liquid argon which moves from a microscopic model and is
applied to the cases of low energy electrons, alpha particles and nuclear
recoils. The model is able to describe precisely several sets of experimental
data available in the literature, over wide ranges of electric field strengths
and kinetic energies and can be easily extended to other particles.
