good quantum number so that states with different total spins but with the same total angular momentum, such as $^3P_1 -^1P_1$ and $^3D_2 -^1D_2$ pairs, can mix via the spin orbit interaction or some other mechanism such as mixing via coupled channels. Consequently, the physical $J=2$ $D$-wave states are linear combinations of $^3D_2$ and $^1D_2$ which we describe by: $$\begin{aligned}
\label{eqn:mixing}
D_{2}  & = {^1D_2} \cos\theta_{nD} + {^3D_2} \sin\theta_{nD} \nonumber \\   
D_{2}^{\prime} & =-{^1D_2} \sin\theta_{nD} + {^3D_2} \cos \theta_{nD} \end{aligned}$$ where $D\equiv L=2$ designates the relative angular momentum of the $q\bar{q}$ pair and the subscript $J=2$ is the total angular momentum of the $q\bar{q}$ pair which is equal to $L$ with analogous expressions for other values of $L$. We obtain $\theta_{1D}=-38.5^\circ$ (for $c\bar{s}$). This notation implicitly implies $L-S$ coupling between the quark spins and the relative orbital angular momentum. In the heavy quark limit (HQL) in which the heavy quark mass $m_Q\to \infty$, the states can be described by the total angular momentum of the light quark, $j_q$, which couples to the spin of the heavy quark and corresponds to $j-j$ coupling. In this limit the state that is mainly spin singlet has $j_q=l+{1\over 2}$ while the state that is 