  We investigate the bound states of the Yukawa potential $V(r)=-\lambda
\exp(-\alpha r)/ r$, using different algorithms: solving the Schr\"odinger
equation numerically and our Monte Carlo Hamiltonian approach. There is a
critical $\alpha=\alpha_C$, above which no bound state exists. We study the
relation between $\alpha_C$ and $\lambda$ for various angular momentum quantum
number $l$, and find in atomic units, $\alpha_{C}(l)= \lambda [A_{1} \exp(-l/
B_{1})+ A_{2} \exp(-l/ B_{2})]$, with $A_1=1.020(18)$, $B_1=0.443(14)$,
$A_2=0.170(17)$, and $B_2=2.490(180)$.
