Explanations for the observed increase in fast electron penetration in laser shock compressed materials

We analyze recent experimental results on the increase of fast electron pen etration in shock compressed plastic [Phys. Rev. Lett. 81, 1003 (1998)]. It is explained by a combination of stopping power and electric field effects , which appear to be important even at laser intensities as low as 10(16) W cm(-2). An important conclusion is that fast electron induced heating must be taken into account, changing the properties of the material in which th e fast electrons propagate. In insulators this leads to a rapid insulator t o conductor phase transition.