  Angular scattering in charge exchange and elastic collisions between
interstellar ions and neutral (ISN) atoms has been assumed to be negligible in
previous studies. Here, we investigated the momentum transfer associated with
the angular scattering of H atoms using Monte Carlo calculations to simulate
their transport through the outer heliosheath. We considered two cases where
charge exchange and elastic collisions between ISN H atoms and protons occur
with and without momentum transfer in the outer heliosheath. We then simulated
the transport of ISN H atoms inside the heliosphere to simulate count rates
observed in the lowest energy bin of IBEX-Lo. We studied the effect of
radiation pressure on the ISN H measurements for the cases with and without
momentum transfer and compared them with our previous findings. We found an
effective radiation parameter ($\mu_{\scriptsize\textrm{eff}}$, which
represents for force associated with radiation pressure relative to gravity)
for the years 2009-2018 based on the longitudinal shift of the ISN H signal.
The two cases with and without momentum transfer reproduce the longitudinal
shift in accordance with variations in solar activity, in agreement with our
previous results, and they result in similar values for the
$\mu_{\scriptsize\textrm{eff}}$, which is $\sim21-22 \%$ larger than the value
found based on Ly$\alpha$ observations.
