Tunnel splittings for one-dimensional potential wells revisited

The Wentzel-Kramers-Brillouin and instanton answers for the tunnel splittin g of the ground state in a symmetric double-well potential are both reduced to an expression involving only functionals of the potential, without the need for solving any auxilliary problems. This formula is applied to simple model problems. The prefactor for the splitting in the textbook by Landau and Lifshitz is amended so as to apply to the ground and low lying excited states. (C) 2000 American Association of Physics Teachers.