We investigate the bound states of the Yukawa potential V(r)=−λexp(−αr)/r, using different algorithms: solving the Schr\"odinger
equation numerically and our Monte Carlo Hamiltonian approach. There is a
critical α=αC, above which no bound state exists. We study the
relation between αC and λ for various angular momentum quantum
number l, and find in atomic units, αC(l)=λ[A1exp(−l/B1)+A2exp(−l/B2)], with A1=1.020(18), B1=0.443(14),
A2=0.170(17), and B2=2.490(180).Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in
China