  A liquid argon time projection chamber, constructed for the Argon Response to
Ionization and Scintillation (ARIS) experiment, has been exposed to the highly
collimated and quasi-monoenergetic LICORNE neutron beam at the Institute de
Physique Nuclaire Orsay in order to study the scintillation response to nuclear
and electronic recoils. An array of liquid scintillator detectors, arranged
around the apparatus, tag scattered neutrons and select nuclear recoil energies
in the [7, 120] keV energy range. The relative scintillation efficiency of
nuclear recoils was measured to high precision at null field, and the
ion-electron recombination probability was extracted for a range of applied
electric fields. Single Compton scattered electrons, produced by gammas emitted
from the de-excitation of $^7$Li* in coincidence with the beam pulse, along
with calibration gamma sources, are used to extract the recombination
probability as a function of energy and electron drift field. The ARIS results
have been compared with three recombination probability parameterizations
(Thomas-Imel, Doke-Birks, and PARIS), allowing for the definition of a fully
comprehensive model of the liquid argon response to nuclear and electronic
recoils down to a few keV range. The constraints provided by ARIS to the liquid
argon response at low energy allow the reduction of systematics affecting the
sensitivity of dark matter search experiments based on liquid argon
