THE NEW-WAVE IN SHOCK-WAVES

Laser-driven shock waves (0-5 GPa) can be generated at high repetition rates (100/s) using a moderate-energy tabletop picosecond laser syste m and a multilayered microfabricated shock target array. High spatial resolution is needed to obtain high temporal resolution of the effects of a steeply rising shock front on molecular materials. The needed sp atial resolution is obtained using a sandwich arrangement with a thin layer of sample material termed an ''optical nanogauge''. Experiments with an anthracene nanogauge show that ultrafast vibrational spectrosc opy can be used to determine the shock temperature, pressure, velocity , and shock front rise time. Shock pulses can be generated with rise t imes <25 ps, which generate irreversible shock compression, and with r ise times of a few hundred picoseconds, which generate reversible comp ression. These pulses, which have a duration of a few nanoseconds, are termed ''nanoshock'' pulses. Nanoshock pulses produce large-amplitude mechanical perturbations and can initiate and turn off thermochemical reactions, produce highly excited vibrational populations, and heat a nd cool condensed matter systems at tremendous rates. These applicatio ns are illustrated briefly in nanoshock experiments on an energetic ma terial and a heme protein. Using high repetition rate nanoshocks to st udy large-amplitude molecular dynamics in molecular materials importan t in chemistry and biology is the new wave in shock waves.