Coupling of Pulsed 0.35 Micrometer Laser Radiation to Titanium Alloys

An experimental and theoretical study has been performed on the response of a Ti alloy (Ti--6Al--4V) surface in vacuum to a XeF laser pulse ( lambda = 0.35 mu m, pulse time = 1 mu s). Thermal coupling measurements indicate an optical absorptance of 0.4-0.5. The onset of a measurable impulse is shown to result from bulk target vaporization for fluences = > 5 J/cm exp 2 . The plasma formation threshold is obtained both theoretically and from experimental data and good agreement is found. The theoretical model includes laser absorption in the target vapor through inverse bremsstrahlung and photoionization absorption and collisional energy transfer between free electrons and bound electronic states of Ti. 18 ref.--AA