  We employ a viable $f(R)$ gravity model capable of giving an inflationary
phase in order to study the subsequent reheating phase due to particle creation
at the expense of energy in the scalaron field. Since quantum mechanics is
expected to play a dominant role in particle creation, we formulate a plausible
scenario of reheating obeying Heisenberg's uncertainty principle that imposes
constraints on the particles created in the configuration space. We show that,
so long as the energy available in the scalaron field is sufficient to populate
the entire configuration space, the energy density of the particles grows,
attaining a maximum value giving an efficient reheating. Beyond this maximum,
the available energy becomes insufficient to populate the entire configuration
space leading to a declining energy density.
  We further find that there is a negligible growth of energy density in the
inflationary phase that lasts for $\sim 10^7 \, t_{\rm P}$, although particles
are constantly created in this phase. The subsequent reheating phase spans for
$\sim10^{11} \, t_{\rm P}$ and it begins with a well-defined preheating stage
lasting for $\sim 10^{5} \, t_{\rm P}$, making a cross-over to a thermilization
regime. The temperature at the beginning of the thermilization is found to be
$T_{\rm th}\sim 10^{12}$ GeV, whereas the reheating temperature is estimated as
$T_{r}\sim10^{13}$ GeV. Importantly, these estimates follow from a single
parameter, the scalaron mass, $M\sim10^{-5} \, M_{\rm P}$.
