  We investigate the behaviour of single-channel theoretical models of cold and
ultracold collisions that take account of inelastic and reactive processes
using a single parameter to represent short-range loss. We present plots of the
resulting energy-dependence of elastic and inelastic or reactive cross sections
over the full parameter space of loss parameters and short-range phase shifts.
We then test the single-channel model by comparing it with the results of
coupled-channel calculations of rotationally inelastic collisions between LiH
molecules and Li atoms. We find that the range of cross sections predicted by
the single-channel model becomes increasingly accurate as the initial LiH
rotational quantum number increases, with a corresponding increase in the
number of open loss channels. The results suggest that coupled-channel
calculations at very low energy (in the s-wave regime) could in some cases be
used to estimate a loss parameter and then to predict the range of possible
loss rates at higher energy, without the need for explicit coupled-channel
calculations for higher partial waves.
