Comments on the JWKB Approximation

The JWKB approximation involved in standard Fowler-Nordheim theory approximates a "quasi-classical potential energy" describing a tunneling probability for an electron approaching a tunneling barrier. Some comments regarding the adequacy of this approximation method are made and the principle of restoring a "pre-factor" into the tunneling probability approximation is argued. JWKB approximation is shown to be applicable in normal circumstances of cold field electron emission