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The amount of heat deposited on an aluminum target after irradiation in air by a KrF laser at 249 nm has been measured to be ∼40% of the incident pulse energy for long pulses (0.5 μsec), moderate flux levels (106–108 W/cm2), and spot diameter ⩾0.5 cm. The impulse generated by the laser has also been measured. Significant impulse levels were observed at low incident fluence levels.

A simplified parametric model of the flowfield produced by impingement of a high-energy laser pulse onto a nonablative surface in a static environment is described. An attempt has been made to account for the twodimensional effects arising out of the rarefaction structure within the laser-heated gases. An optimization model is developed to indicate the laser spot size, pulse width, and intensity dependencies of the efficiency of delivery of both impulse and mechanical energy to the target surface.velocity u(x) = axial velocity v = velocity behind shock in LSC model V w = LSC wave speed W = nondimensional particle velocity x = axial coordinate a =(Kt) y = ratio of specific heats in plasma 70 = ratio of specific heats in air p = density o = target material density Tf) = pulse length T Z = axial relaxation time T 2D = radial relaxation time T = normalized pulse time (= r p /r 2D ) T O = pressure relaxation time $0 = incident laser flux intensity, W/cm 2 Subscripts LSC = laser supported combustion condition LSD = laser supported detonation condition 0 = ambient r = condition behind rarefaction s = surface, spot

The interaction of XeF laser radiation at 353 nm with an aluminum target in air at reduced (0.1 Torr) and ambient pressures has been studied. The thermal coupling at moderate fluxes (106–108 W/cm2) and long pulse length at 0.1 Torr was found to be ∼20%. Impulse coupling was also determined.