Infrared multiphoton absorption and electronic polarizability

The effect of electronic polarizability on the absorption of infrared photons by diatomic molecules in an intense laser field is investigated by numerically simulating the time evolution of the system. The absorption spectrum has a frequency shift proportional to the intensity; its dependence on polarizability and anharmonicity is established. It is shown that for pulsed fields the effect of polarizability is irregularly dependent on the pulse length. Resonances in the half-frequency range are strongly enhanced by the electronic polarizability.