ABSTRACT
Laser systems delivering superintense ultrashort pulses are available in numerous laboratories. A simple classical estimate reveals that under the action of the strong laser field the first bound electrons are removed in a fraction of an oscillation. The most important consequence of the one-dimensional model is probably the insight that the contribution to ionisation from tunneling is weak in fast rising laser pulses and, hence, classical models should yield satisfactory results. Field ionisation by superintense laser pulses was proposed as a method to generate cold plasmas of overthermal degree of ionisation to create inversion in the UV or soft X-ray regime. When a free electron initially at rest is exposed to a laser pulse it starts oscillating and is shifted by the ponderomotive force. When the pulse is over, the electron is again at rest at a different position. An electron bound in the atom undergoes very weak oscillations in the laser field.
