Abstract

It is widely accepted now that the harmonics generated by an atomic electron that escapes by tunneling and then recombines back to the core form a plateau extending up to I_p + 3.2U_p, where I_p is the ionisation potential and U is the mean kinetic energy of a free electron n the laser field. In the present communication we want to show that this cutoff law may extend up to I_p + 8U_p in the case where ionisation and recombination occur at different places. In particular we consider a molecule stretched well beyond the equilibrium distance, showing that it yields harmonic peaks of much higher orders than those produced by an isolated atom or the same molecule with the cores located close to their equilibrium distance.

© 1996 Optical Society of America