  We study the charmonium ($c\bar{c}$) and bottomonium ($b\bar{b}$) spectra,
using Cornell potential with additional constant potential term in a
non-relativistic framework, with spin-dependent corrections corresponding to
the spin-spin, spin-orbit, and tensor interactions added perturbatively. We
predict the masses of low-lying and excited states of charmonium and
bottomonium up to $n=6$ and $L=2$. We analyze the radial and orbital Regge
trajectories of both the systems and investigate their departure from
linearity. Further, we estimate the wave function at the origin and,
consequently, predict the decay widths of charmonium and bottomonium states
annihilating to leptons and photons. Also, we investigate the effect of scale
dependence of the wave function at the origin and the strong coupling constant
on the predictions of annihilation decay widths. We compare our predictions of
heavy quarkonium spectra and decay widths with experimental results and other
theoretical models.
