Investigation into the surface relief grating mechanism via XPS in new azobenzene based optical material

Research into azobenzene and its compounds focuses on the molecules ability to cis‐trans isomerize, this photoisomerization enables surface relief gratings (SRGs) to be formed on the azobenzene functionalized polymer films. SRG allows information to be written and then erased, an essential requirement of most modern electrical products. The interest into SRG photofabrication is thus rapidly increasing and is emerging at the forefront of photonic and nanotechnology research. The surface relief grating mechanism, however, is not fully understood, a photoplasticization process is postulated, which is thought to occur via the azo‐chromophores photoisomerization, so encouraging polymer chain migration to the surface. In comparison, suggestions have shown the SRG process does not involve a change in the film surface profile but in the local refractive index. Currently, no research has yet established the surface relief grating mechanism, this paper sets out to determine the mechanism and investigate those theories already postulated by observing the thin film surfaces prior to and after SRG using X‐ray photoelectron spectroscopy (XPS). By identifying the surface components, greater insight and understanding of the SRG mechanism can be achieved. In this paper, poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)₉₀‐co‐(methylmethacrylate)₁₀ 50 : 50 PMMA blend was exposed to SRGs. Using XPS the surface composition was determined prior to and after SRG. Following SRG, the spectra for O 1s, N 1s and C 1s using XPS expressed a change in the components at the surface. This is most evident in the N 1s spectra, with PMMA not containing nitrogen, the N 1s becomes the determining factor. The nitrogen absence combined with a significant increase in the carbon and oxygen peak intensity concludes the azobenzene lies not on the surface but, in fact, within the bulk after SRG. The initial light irradiation process must be a consideration. However, on X‐ray analysis the sample showed the same spectra as the one prior to SRG. Copyright © 2002 John Wiley & Sons, Ltd.     

Weighted inequalities for iterated maximal functions in Orlicz spaces

Let M be the classical Hardy‐Littlewood maximal operator. The object of our investigation in this paper is the iterated maximal function M^kf(x) = M(M^k?1f) (x) (k ≥ 2). Let Φ be a φ‐function which is not necessarily convex and Ψ be a Young function. Suppose that w is an A′_∞ weight and that k is a positive integer. If there exist positive constants C₁ and C₂ such that ((I)) then there exist positive constants C₃ and C₄ such that ((II)) where the functions a(t) and b(t) are the right derivatives of Φ(t) and Ψ(t), respectively. Conversely, if w is an A₁ weight, then (II) implies (I). Another necessary and sufficient condition will be given. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Surface-enhanced Raman scattering as a probe for exotic electronic excitations induced by localized surface plasmons

Exotic electronic excitations beyond normal selection rules would open novel possibilities for photoenergy conversion. The large intensity gradient of electromagnetic fields resulting from the confinement of localized surface plasmons at the molecular scale could exceed the limit of light–matter interactions via modification of electronic excitation selection rules. We discuss the possible application of surface-enhanced Raman scattering as a probe for exotic electronic excitations by reviewing studies on small numbers of molecules at the surface of plasmonic metal nanostructures. Future innovative photo-functionalization is also discussed by considering the excited states produced by the exotic electronic excitations.     

Two‐dimensional correlation gel permeation chromatography study of aggregate–aggregate interactions during acid‐catalyzed polymerization of triethoxysilyl‐terminated polystyrene

The three‐step polymerization of a well‐defined polymeric silane coupling agent, triethoxysilyl‐terminated polystyrene, catalyzed by acid (H₃PO₄), was traced as a function of the reaction time with gel permeation chromatography (GPC). Time‐resolved GPC traces collected during the polymerization process were then used to construct two‐dimensional (2D) correlation maps via generalized 2D correlation analysis. The results demonstrated that the synchronous and asynchronous 2D correlation GPC spectra directly reflected the dynamic variation of aggregate–aggregate interactions during each step of the polymerization. In particular, it was found that the formation of aggregates among the cyclic trimers (or tetramers) and monomers was critical for the preferential production of pentamers in the reaction system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3447–3460, 2004     

Picosecond time-resolved luminescence of hydrogenated amorphous silicon-carbon

Photoluminescence decay curves and time-resolved luminescence spectra of amorphous Si_0.15C_0.85 : H films are measure. The decay curves are nearly exponential with a time-constant of about 200 psec at room temperature. The peak of the emission spectrum is shifted from 440 nm immediately after the excitation to 490 nm at 400 psec after the excitation.     

A Square‐Planar Complex of Platinum(0)

The Pt⁰ complex [Pt(PPh₃)(Eind₂‐BPEP)] with a pyridine‐based PNP‐pincer‐type phosphaalkene ligand (Eind₂‐BPEP) has a highly planar geometry around Pt with ∑(Pt)=358.6°. This coordination geometry is very uncommon for formal d¹⁰ complexes, and the Pd and Ni homologues with the same ligands adopt distorted tetrahedral geometries. DFT calculations reveal that both the Pt and Pd complexes are M⁰ species with nearly ten valence electrons on the metals whereas their atomic orbital occupancies are evidently different from one another. The Pt complex has a higher occupancy of the atomic 6s orbital because of strong s–d hybridization due to relativistic effects, thereby adopting a highly planar geometry reflecting the shape and orientation of the partially unoccupied orbital.     

Evidence for in-medium modification of the phi meson at normal nuclear density

Invariant mass spectra of e(+) e(-) pairs have been measured in 12 GeV p + A reactions to detect possible in-medium modification of vector mesons. Copper and carbon targets are used to study the nuclear-size dependence of e(+) e(-) invariant mass distributions. A significant excess on the low-mass side of the phi meson peak is observed in the low betagamma(= beta/square root(1-beta(2))) region of phi mesons (betagamma < 1.25) with copper targets. However, in the high betagamma region (betagamma > 1.25), spectral shapes of phi mesons are well described by the Breit-Wigner shape when experimental effects are considered. Thus, in addition to our earlier publications on rho/omega modification, this study has experimentally verified vector meson mass modification at normal nuclear density.     

Numerical experiments of the planar equal-mass three-body problem: the effects of rotation

The planar three-body problem with angular momentum is numerically and systematically studied as a generalization of the free-fall problem (i.e., the three-body problem with zero initial velocities). The initial conditions in the configuration space exhaust all possible forms of a triangle, whereas the initial conditions in the momentum space are chosen so that position vectors and momentum vectors are orthogonal. Numerical results are organized according to the value of virial ratio k defined as the ratio of the total kinetic energy to the total potential energy. Final motions are mapped in the initial value space. Several interesting features are found. Among others, binary collision curves seem to spiral into the Lagrange point, and for large k, binary collision curves connect the Lagrange point and the Euler point. The existence of a lunar periodic orbit and a periodic orbit of petal-type is suggested. The number of escape orbits as a function of the escape time is analyzed for different k. The behavior of this number for different time and k shows most remarkably the effects of rotation of triple systems. The number of escape orbits increases exponentially for k相似文献   

Arrangements of n Points whose Incident-Line-Numbers are at most n/2

We consider a set X of n noncollinear points in the Euclidean plane, and the set of lines spanned by X, where n is an integer with n ≥ 3. Let t(X) be the maximum number of lines incident with a point of X. We consider the problem of finding a set X of n noncollinear points in the Euclidean plane with t(X) ￡ ?n/2 ?{t(X) \le \lfloor n/2 \rfloor}, for every integer n ≥ 8. In this paper, we settle the problem for every integer n except n = 12k + 11 (k ≥ 4). The latter case remains open.