Optical characterisation of the photolytic decomposition of ferrocene into nanoparticles

Optical emission from the photolytic dissociation of ferrocene Fe(C₅H₅)₂, often abbreviated as FeCp₂, in argon atmosphere was studied. The dissociation was performed by using an ArF excimer laser, operating at a wavelength of 193 nm. Two pressure regions were examined. At low (0.1 mbar) pressure, several emission lines of Fe could be identified, however no C, C₂, or CH emission lines/bands were found. At a higher (20 mbar) pressure of the FeCp₂/Ar gas mixture, a broadband emission identified as blackbody radiation was observed. This blackbody radiation originates from nanoparticles with a mean size of 30 nm, which consist of both metallic iron and amorphous carbon. The initial colour temperature of the particles was 2600 K.     

Confocal scanning microfluorometry of dual-labelled specimens using two excitation wavelengths and lock-in detection technique

A new technique for simultaneous recording of multiple fluorophores has been implemented in a confocal scanning laser microscope. Dual excitation wavelengths, intensity-modulated at different frequencies and two lock-in amplifiers tuned to the corresponding frequencies are used. In this way two fluorophores can be independently, albeit simultaneously, excited. This technique, Intensity-modulated Multiple-beam Scanning (IMS) microfluorometry, has the potential to virtually eliminate the cross-talk between fluorophores that often occurs when recording multiple-labelled specimens. Furthermore, it will offer simultaneous information about both the excitation and emission spectra of the fluorophores used. Also, variations in decay time over the image area can be studied independently and simultaneously for two fluorophores.     

Oriented polyolefin laminates: A refractometry and infrared study

A series of polypropylene-copolymer laminates produced by biaxial orientation in the 120–155°C range has been characterized by refractometry and infrared (IR) spectroscopy. The copolymer was a random ethylene-propylene resin and the IR techniques included tilted-film transmission as well as internal reflection, both using polarized radiation. The IR techniques yielded spectra corresponding to the machine, transverse, and through directions. Similarly, the refractometry gave refractive indices of both components of each laminate along all three axes. Results from the three techniques were compared and contrasted and the validity of the calculated internal reflectance spectra discussed. Practical methods to estimate the source and extent of errors in the latter technique from false radiation and contact problems were explored.     

The Theory of Multidimensional Persistence

Persistent homology captures the topology of a filtration—a one-parameter family of increasing spaces—in terms of a complete discrete invariant. This invariant is a multiset of intervals that denote the lifetimes of the topological entities within the filtration. In many applications of topology, we need to study a multifiltration: a family of spaces parameterized along multiple geometric dimensions. In this paper, we show that no similar complete discrete invariant exists for multidimensional persistence. Instead, we propose the rank invariant, a discrete invariant for the robust estimation of Betti numbers in a multifiltration, and prove its completeness in one dimension. The first author was partially supported by NSF under grant DMS-0354543. The second author was partially supported by DARPA under grant HR 0011-06-1-0038 and by ONR under grant N 00014-08-1-0908. Both authors were partially supported by DARPA under grant HR 0011-05-1-0007.     

Second-harmonic generation in vortex-induced waveguides

We study the second-harmonic generation and localization of light in a reconfigurable waveguide induced by an optical vortex soliton in a defocusing Kerr medium. We show that the vortex-induced waveguide greatly improves conversion efficiency from the fundamental to the second-harmonic field.     

Very high crystalline quality of thick 4H‐SiC epilayers grown from methyltrichlorosilane (MTS)

200 µm thick 4H‐SiC epilayers have been grown by chloride‐based chemical‐vapor deposition using methyltrichlorosilane (MTS) as single precursor. The very high crystalline quality of the grown epilayer is demonstrated by high resolution X‐Ray Diffraction rocking curve with a full‐width‐half‐maximum value of only 9 arcsec. The high quality of the epilayer is further shown by low temperature photoluminescence showing strong free exciton and nitrogen bound exciton lines. The very high crystalline quality achieved for the thick epilayer grown in just two hours at 1600 °C suggests that MTS is a suitable precursor molecule for SiC bulk growth. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vector solitons in (2 + 1) dimensions

We address the problem of the existence and stability of vector spatial solitons formed by two incoherently interacting optical beams in bulk Kerr and saturable media. We identify families of (2+1)-dimensional two-mode self-trapped beams, with and without a topological charge, and describe their properties analytically and numerically.     

Der Multiplikator von Thetareihen höheren Grades zu quadratischen Formen ungerader Ordnung

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