Abstract

The desorption of organic molecules from condensed van der Waals films with IR photons^1-3 and the ablation of organic material from the Chemical network of organic polymers wlth UV photons⁴ have found much interest recently. There is, however, a controversial discussion concerning the mechanism of the laser-induced processes in each case. For desorption of molecules by resonant excitation of internal vibratlonal modes with an IR laser, quantum desorption as well as photothermal desorption has been considered. For ablation of organic material with UV lasers, photochemical as well as photothermal or combined mechanisms is discussed. It is shown that despite the different photon energies (IR and UV) and the different binding energies (van der Waals and Chemical bond), the main features of these different experiments can be understood in terms of a photothermal mechanism governing the processes which follow specific laser excitation and a possible primary photodissociation in the case of UV radiation. This unified treatment includes the wavelength dependence of the desorption yield and the translational temperatura for IR desorption, the threshold behavior observed in both systems, and the velocity and fluence dependence of the ablated material as well as the angle dependence in the case of UV ablation.

© 1986 Optical Society of America