Abstract

Using sub-100 fs laser pulses it is possible to excite and probe nuclear motions in liquids on a time scale that is short compared to the mean collision time. Optical Kerr effect [1] and transient grating scattering [2] experiments have shown that molecules are inertial. Due to their finite moment of inertia they cannot follow the ultrashort laser pulse and hence the response possesses a finite rise time of typically ±100 fs. The coherently excited librations dephase rapidly within the next 1 to 2 ps. On a longer time scale the material response is completely determined by rotational diffusion showing up as an exponential decay.

© 1996 IEEE