  We present the results of experimental and theoretical study of the
scattering of low energy p$\mu$ atoms in solid hydrogen cooled to 3 K. The
resulting emission of low energy p$\mu$ atoms from the hydrogen layer into the
adjacent vacuum was much higher than that predicted by calculations which
ignored the solid nature of the hydrogen. New differential scattering cross
sections have been calculated for the collisions of p$\mu$ atoms on solid
hydrogen to acount for its quantum crystalline nature. Analysis of the
experimental data performed using such cross sections shows the important role
of the coherent scattering in p$\mu$ atom diffusion. For p$\mu$ energies lower
than the Bragg cutoff limit (2 meV) the elastic Bragg scattering vanishes which
makes the total scattering cross section fall by several orders of magnitude,
and thus the hydrogen target becomes transparent allowing the emission of cold
p$\mu$ atoms to occur.
