A Kronig-Penky model with a constant elecrric field F for a non-interacting electron is used to study the msmission properties of the Anderson transition in one-dimensional systems with disordered &function potentials. We examine the cues where the potential varies uniformly from 0 to W (barriers) or from -W to 0 (wells) for a given disorder W. We observe jumps in the transmission coefficient at the points E + Fx = n2nz (where E is the electron energy and n an integer). These jumps are related to the small oscillations observed by Soukoulis et nf in the mixed m e (potentials from -WIZ to WIZ). However. an interesting feature is found in the wells in the range between two jumps. It is observed that in the presence of a small field the states become more localized and the localization length decreases up to a minimum for a critical value F, instead of increasing. Finally, we have studied thc effect of the disorder on the Anderson transition by means of the participation nfio and the localization length.

The ablation of poly(ethylene terephthalate) (PET) by Ar-F laser radiation has been studied at different fluences for amorphous and semicrystalline samples by scanning electron microscopy (SEM) and by etch-depth measurements. The surface structure created on PET has been interpreted as resulting mainly from a difference in the etch rate—and not the ablation threshold—between amorphous and semicrystalline PET. SEM pictures clearly show the melting of the PET surface at high fluence (≥80 to 100 mJ/cm2) and not below that value. UV laser etching is proposed as a quick and easy method for observing the crystalline subsurface structure of aromatic semicrystalline polymers, as long as low fluence and a low pulse repetition rate are used.

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