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11.
M. Keil T. Kolling K. Bergmann W. Meyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):55-64
The process of dissociative attachment (DA) of low-energy electrons ) to vibrationally excited sodium dimer molecules is studied with high electron energy resolution () in a supersonic molecular beam. A novel photoelectron source, based on two-step photoionization of the sodium atoms in the
beam, may deliver a current of up to 1 nA and has been used with a current of typically 0.2 nA in this experiment. The energy
dependence of the rate of sodium anion formation is determined by ion detection based on a time-of-flight analysis. The molecules
are selectively excited to levels using the technique of coherent population transfer by delayed pulses (STIRAP). The comparison of the experimental data with
recent resonance model calculations based on improved potential curves reveals generally good agreement for levels v
”>12. For some distinct differences between theoretical and experimental results persist.
Received: 21 November 1998 / Received in final form: 7 April 1999 相似文献
12.
During the last 50 years extensive experimental investigation has been carried out on the chemical effects of ultrasound, but limited work has been reported on modeling. This paper presents a new model in which a numerical calculation of the three-dimensional linear sound pressure field distribution in a commonly used sonoreactor containing three transducers is carried out. In this model the inhomogeneous three-dimensional time-dependent wave equation was solved using the finite difference approach. The modeled results are then compared with the experimentally measured values, and the agreement, in general, is found to be good. Further, our modeling studies have an advantage, since they clearly describe the continuous sound pressure field structure, unlike previously reported results in which some information is missing due to limited intermittent measured points. 相似文献
13.
Analytical and Bioanalytical Chemistry - Durch Benutzung eines pH-Wertes von 2,5 und Anwendung verschiedener Maskierungsmittel kann die extraktive spektralphotometrische Bestimmung von Ga mit... 相似文献
14.
15.
The fluorescence mode confocal laser scanning microscopy (CLSM) is introduced as an alternative method to investigate the
bulk structure of poly(vinyl alcohol) (PVA) hydrogel. Investigations of the bulk structure of hydrogel samples, prepared by
freezing and controlled thawing of aqueous PVA solutions followed by fluorochrome conjugation, were possible in the native
state because with this technique water does not need to be removed prior to examination. This is of advantage to other methods,
such as scanning electron microscopy, requiring dehydration by critical-point drying or freeze-etching, because both may result
in a significant alteration of the gel structure. CLSM images of the hydrogel bulk structure were taken at several successive
intervals from the surface into the hydrogel (up to 60 μm) without freeze-fracturing or cutting the sample. Detailed morphological
characterization is achievable by superimposing series of images taken at successive intervals and by magnifying special regions
of interest. Images of hydrogel bulk structures revealed a continuous, three-dimensional network that originates from phase-separation
(spinodal decomposition) during the freezing period. The pore or mesh size in the cryogel increased, from about 2–7 μm, with
decreasing PVA concentration. The surface layer was only a few microns thick, and the bulk structure underneath showed neither
porosity gradients nor structural orientations.
Received: 29 April 2000/Accepted: 18 August 2000 相似文献
16.
Keil R Perez-Leija A Dreisow F Heinrich M Moya-Cessa H Nolte S Christodoulides DN Szameit A 《Physical review letters》2011,107(10):103601
Coherent states and their generalizations, displaced Fock states, are of fundamental importance to quantum optics. Here we present a direct observation of a classical analogue for the emergence of these states from the eigenstates of the harmonic oscillator. To this end, the light propagation in a Glauber-Fock waveguide lattice serves as equivalent for the displacement of Fock states in phase space. Theoretical calculations and analogue classical experiments show that the square-root distribution of the coupling parameter in such lattices supports a new family of intriguing quantum correlations not encountered in uniform arrays. Because of the broken shift invariance of the lattice, these correlations strongly depend on the transverse position. Consequently, quantum random walks with this extra degree of freedom may be realized in Glauber-Fock lattices. 相似文献
17.
We show that the geometrically induced potential existing in undulated slab waveguides dramatically affects the properties of solitons. In particular, whereas solitons residing in the potential maxima do not feature power thresholds and are stable, their counterparts residing in the potential minima are unstable and may exhibit a power threshold for their existence. Additionally, the geometric potential is shown to support stable multipole solitons that cannot be supported by straight waveguides. Finally, the geometric potential results in the appearance of the effective barriers that prevent transverse soliton motion. 相似文献
18.
Miller SA Hiatt LA Keil RG Wright DW Cliffel DE 《Analytical and bioanalytical chemistry》2011,399(3):1021-1029
Immunoassays are important tools for the rapid detection and identification of pathogens, both clinically and in the research
laboratory. An immunoassay with the potential for the detection of influenza was developed and tested using hemagglutinin
(HA), a commonly studied glycoprotein found on the surface of influenza virions. Gold nanoparticles were synthesized, which
present multiple peptide epitopes, including the HA epitope, in order to increase the gravimetric response achieved with the
use of a QCM immunosensor for influenza. Specifically, epitopes associated with HA and FLAG peptides were affixed to gold
nanoparticles by a six-mer PEG spacer between the epitope and the terminal cysteine. The PEG spacer was shown to enhance the
probability for interaction with antibodies by increasing the distance the epitope extends from the gold surface. These nanoparticles
were characterized using thermogravimetric analysis, transmission electron microscopy, matrix-assisted laser desorption/ionization-time
of flight, and 1H nuclear magnetic resonance analysis. Anti-FLAG and anti-HA antibodies were adhered to the surface of a QCM, and the response
of each antibody upon exposure to HA, FLAG, and dual functionalized nanoparticles was compared with binding of Au–tiopronin
nanoparticles and H5 HA proteins from influenza virus (H5N1). Results demonstrate that the immunoassay was capable of differentiating
between nanoparticles presenting orthogonal epitopes in real-time with minimal nonspecific binding. The detection of H5 HA
protein demonstrates the logical extension of using these nanoparticle mimics as a safe positive control in the detection
of influenza, making this a vital step in improving influenza detection methodology. 相似文献
19.
Short-pulse optical sources have allowed the study of ultrafast electrical phenomena in the circuits and devices which will become future electronic systems. In this paper techniques for the generation, propagation and detection of electrical signals in the femtosecond regime are presented. 相似文献
20.
Theoretical rate constants have been calculated for O(3P) with five saturated hydrocarbons, CH4, C2H6, C3H8, iso-C4H10, and neo-C5H12. The method of choice is bond energy–bond order (BEBO) with activated complex theory (ACT). Because the BEBO method is empirical, O(3P) + CH4 is evaluated first, and the theoretical results are compared to more rigorous calculations and to the empirical transition state method. Comparisons are also made between predictions and experimental results. All of these comparisons show that the BEBO-ACT method gives results which are consistent with experiment and other theory. Because the method is successful, the other four cases are then considered. Ambiguity arises for the higher hydrocarbons from the problem of internal rotations in the activated complexes, and three cases are evaluated. Best agreement with experiment is obtained if the primary rotor(s) in the complexes are considered to be free. Predictions of rate constants are made from 500 to 2500 K. Throughout the discussion issues of theory which are common to any ACT calculation from any method of potential energy evaluation (LEP, LEPS, or ab initio quantum mechanics) are featured. 相似文献