The extremely small probability of tunneling through an almost classical potential barrier may become not small under the action of the specially adapted nonstationary signal which selects the certain particle energy [Formula Presented] For particle energies close to this value, the tunneling rate is not small during a finite interval of time and has a very sharp peak at the energy [Formula Presented] After entering inside the barrier, the particle emits electromagnetic quanta and exits the barrier with a lower energy. The signal amplitude can be much less compared to the field of the static barrier. This phenomenon can be called the Euclidean resonance since the under-barrier motion occurs in imaginary time. The resonance may stimulate chemical and biochemical reactions in a selective way by adapting the signal to a certain particular chemical bond. The resonance may be used in search of the soft-α-particle decay for which a conventional observation is impossible due to an extremely small decay rate. 5555 2002 The American Physical Society.
