No abstract

No abstract

No abstract

We have developed a simple model to estimate the cumulative absorption coefficient of an ultraviolet laser pulse impinging on a pure metal, including the effects of surface roughness whose scale is much larger than the laser wavelength. The multiple reflections from the rough surface may increase the absorption coefficient over a pristine, flat surface by an order of magnitude. Thus, as much as 16% ͑at room temperature͒ of the power of a 248 nm KrF excimer laser pulse may be absorbed by an aluminum target. A comparison with experimental data is given.

O. IntroductionThis paper originated from two quite different generalizations of mathematical instanton bundles on P3(C) and their geometry. Since F2, + 1(C) can be considered as a twister space over the quaternionic manifold IP,(~I), a paper of Salamon, I-S], motivated the construction of holomorphic rank-2n bundles on P2,+1(~) by Okonek and the first author in [OS]. These bundles carry an additional holomorphic symplectic form and are generalizations of the special instanton bundles over P3(~), which are also called special 't Hooft bundles in [HN-J. On the other hand B6hmer and the second author, [BT], found that the latter can be interpreted geometrically by certain Poncel6t curves of higher degree related to certain conics. Such Poncel6t curves had been considered by Darboux in IDa] and I-Ba]. the description of the Poncel6t curves led in IT] to a generalization of Darboux's Poncel6t theorem to the case of hypersurfaces, which are Poncel& related to rational normal curves. In this paper the two kinds of objects are linked together by showing that the special instanton bundles of I'OS] are characterized by Poncel6t hypersurfaees, which are related to linear systems on rational normal curves in a Grassmannian.The first part of this paper on the geometry of special instanton bundles is based on the preprint [ST] and gives a systematic account of these bundles. The second part deals with moduli of special instanton bundles.The main result of the first part is Theorem 5.6. The divisor of jumping lines and the bundle itself are determined by a hypersufface Y, contained in a characteristic 2n-dimensional linear subspace of FA ar 3Gr2C2,+2, and Poncel6t related to the rational normal curve C, which is cut' out of the Grassmannian by the 2n-plane and which describes the set of unstable hyperplanes of the bundle.This result not only generalizes the by now classical description of M(0, 2) by Hartshorne, [H1], in all of its aspects. In the course of proving, all special properties of the special instanton bundles have found their natural interpretation in a geometry, which is closely related to linear systems on rational normal curves and a series of operators between SL(2)-representations related to them.