Impulse loading of targets by subnanosecond laser pulses

Measurements of the impulse received by graphite and aluminum targets exposed to a 250-psec laser pulse are reported. Experiments were conducted in air and vacuum at incident energies between 0 and 20 J. In both environments, there is a definite energy threshold, which is lower in air than in vacuum, below which no momentum is transferred. For a given energy above threshold, the impulse generated in air is greater than in vacuum.