Resonant $dd\mu$ Formation in Condensed Deuterium

The rate of $dd\mu$ muonic molecule resonant formation in $d\mu$ atom collision with a condensed deuterium target is expressed in terms of a single-particle response function. In particular, $dd\mu$ formation in solid deuterium at low pressures is considered. Numerical calculations of the rate in the case of fcc polycrystalline deuterium at 3 K have been performed using the isotropic Debye model of solid. It is shown that the energy-dependent $dd\mu$ formation rates in the solid differ strongly from those obtained for D$_2$ gaseous targets, even at high $d\mu$ kinetic energies. Monte Carlo neutron spectra from $dd$ fusion in $dd\mu$ molecules have been obtained for solid targets with different concentrations of ortho-D$_2$ and para-D$_2$. The neutron time spectra calculated for pure ortho-D$_2$ and para-D$_2$ targets are very similar.