A dynamic source effect that accelerates the expansion of laser-ablated material in the direction perpendicular to the target is demonstrated. A self-similar theory shows that the maximum expansion velocity is proportional to $\frac{c_s}{\alpha }$, where $1-\alpha$ is the slope of the velocity profile and $c_s$ is the sound speed. Numerical hydrodynamic modeling is in good agreement with the theory. A dynamic partial ionization effect is also studied. With these effects, $\alpha$ is reduced and the maximum expansion velocity is significantly increased over that found from conventional models.

• Received 22 August 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.4706