On the Stability of the Neutral Meson

' 'N the accompanying letter by Germer and Haworth, ~ evidence is presented to show that a positive ion in a high field (~107 volts/cm) must be able to eject several electrons from a metal. On the other hand, present theories of ejection by positive ions in low fields require that the ion be neutralized as the first step in the ejection process and, hence, that an ion be unable to eject more than one electron. ' If the hypothesis of Germer and Haworth is correct, the mechanism must be qualitatively different at high fields. A positive ion near the surface of a metal creates a deep well in the potential energy function of an electron, and, if the ion is close to the metal, an electron can readily tunnel from the metal to the ion. At low fields, the electron has no place else to go and either remains on the ion, thus neutralizing it, or returns to the metal. At high fields the picture is different. One readily sees that the potential energy surface of the electron has a "pass" lying on the opposite side of the ion from the metal. If the field is suKciently high, the energy at the pass is lower than the Fermi level in the metal. An electron coming from near the Fermi level can then escape to infinity. Thus an electron has become free by tunneling through the barrier between the metal and the ion, which is easier than tunneling through the barrier which exists when the field alone is present. To get some idea of the emission caused by such a process, we have made some calculations based on a onedimensional metal. The electrons inside the metal were assumed to occupy the energy levels of an electron in a box, with the highese energy 4.2 volts below vacuum. Letting r be the distance from the metal surface, we took the potential due to the metal to be: