Analysis of a case of field-induced unit transmissivity in resonant tunneling

We consider two barriers enclosing a well that possesses a bound state. In the presence of an oscillating field, this bound state is transformed into a resonance with a width reflecting the escape process by absorption of quanta from the field. We show that a particle incident on this device with an energy just one quantum above the bound-state energy has a transmissivity approaching unity as the amplitude of the field is reduced. The conditions for efficient transmission at this energy are examined.