  Scintillation and ionisation yields for nuclear recoils in liquid xenon above
10 keVnr (nuclear recoil energy) are deduced from data acquired using broadband
Am-Be neutron sources. The nuclear recoil data from several exposures to two
sources were compared to detailed simulations. Energy-dependent scintillation
and ionisation yields giving acceptable fits to the data were derived.
Efficiency and resolution effects are treated using a light collection Monte
Carlo, measured photomultiplier response profiles and hardware trigger studies.
A gradual fall in scintillation yield below ~40 keVnr is found, together with a
rising ionisation yield; both are in good agreement with the latest independent
measurements. The analysis method is applied to both the most recent ZEPLIN-III
data, acquired with a significantly upgraded detector and a
precision-calibrated Am-Be source, as well as to the earlier data from the
first run in 2008. A new method for deriving the recoil scintillation yield,
which includes sub-threshold S1 events, is also presented which confirms the
main analysis.
