LASER-ABLATION OF POLYSULFONE FILMS - A LASER IONIZATION TOF MASS-SPECTROMETRIC STUDY

We have applied laser ionization time-of-flight (TOF) mass spectrometr y to ablation of polysulfone (PS) with 266 nm laser light at fluences of 20-60 mJ/cm(2). Major peaks were assigned to direct fragments and r ecombination products ejected from the PS surface. The arrival profile s of these ablation products varied from product to product and were f itted by using a shifted Maxwell-Boltzmann distribution with a center- of-mass flight velocity [(1.4 - 5.6) x 10(5) cm/s] and a Knudsen layer temperature (350-3810 K). Two types of ablation products, whose veloc ities and temperatures showed different dependences on laser fluence, were found to exist. Dynamical aspects in the decomposition of the pol ymer chain, the ejection of various fragments, and their expansion are discussed on the basis of a photothermal ablation model, where a heat ed surface layer with a temperature gradient along its depth plays an important role.