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31.
D. Steinmetz E. Neu J. Meijer W. Bolse C. Becher 《Applied physics. B, Lasers and optics》2011,102(3):451-458
We present investigations on single Ni/Si related color centers produced via ion implantation into single crystalline type IIa CVD diamond. By testing different ion dose combinations we show that there is an upper limit for both the Ni and the Si dose (1012 cm?2 and 1010 cm?2 resp.) due to the creation of excess fluorescent background. We demonstrate creation of Ni/Si related centers showing emission in the spectral range between 767?nm and 775?nm and narrow line-widths of ??2?nm FWHM at room temperature. Measurements of the intensity autocorrelation functions prove single-photon emission. The investigated color centers can be coarsely divided into two groups: Drawing from photon statistics and the degree of polarization in excitation and emission, we find that some color centers behave as two-level, single-dipole systems whereas other centers exhibit three levels and contributions from two orthogonal dipoles. In addition, some color centers feature stable and bright emission with saturation count rates up to 78?kcounts/s whereas others show fluctuating count rates and three-level blinking. 相似文献
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A mode-coupling theory (MCT) is presented for the spin-boson model with a spectral density which accounts for a heat bath made up of lattice vibrations of a dielectric solid (superohmic dissipation). A usual decoupling approximation provides a set of non-linear integral equations which are solved both numerically by iteration on a computer and analytically by means of a frequency dependent ansatz for the memory functions. There is a transition to incoherent motion at a temperatureT
* where the bare two-level energy is equal to the damping rate, in contradiction to results obtained previously from a path integral formulation. The discrepancy arises since in the MCT the relevant self-energy function does not exhibit a 1/z-pole atz=0. For tunnelling systems in dielectrics this yields a new relaxation mechanism due to incoherent tunnelling: the present results might require to modify some of the basic assumptions of the standard tunnelling model for dielectric glasses. 相似文献
34.
A classic problem, the design of the tallest column, is solved again using a different method. By the use of a similarity solution the equations are transformed and the difficult singularity at the endpoint is peeled away. The resulting autonomous system has a critical point and the solution must be on its stable manifold. The solution is found by starting near the critical point in the direction of the stable manifold, and solving backward numerically. This removes the need for an iterative integration method that was previously used. The method is shown to work for clamped or hinged boundary condition and can also be used for other problems involving singularities at the endpoints. 相似文献
35.
E. Arnold J. Bonn W. Neu R. Neugart E. W. Orten The Isolde Collaboration 《Zeitschrift für Physik A Hadrons and Nuclei》1988,331(3):295-298
The quadrupole interaction of nuclear spin polarized8Li (I=2) and9Li (I=3/2) in LiNbO3 has been studied at room temperature. The polarization was achieved by optical pumping of a fast atomic beam with circularly polarized laser light. The atoms were implanted into a hexagonal LiNbO3 single crystal and the quadrupole splitting ofβ-NMR spectra was measured. A ratio of ¦Q(9Li)/Q(8Li)¦=0.88(4) for the nuclear quadrupole moments was deduced, yielding a new value of ¦Q(9Li)¦=25.3 (9) mb for the quadrupole moment of9Li. 相似文献
36.
Analytical and Bioanalytical Chemistry - Besides 83 structurally defined trichloro- to octachloro-biphenyls (PCB), the following chlorinated pesticides have been identified in fish liver oil (DAB... 相似文献
37.
H. Hulpke W. Merz H. -J. Neu R. Wilmes 《Fresenius' Journal of Analytical Chemistry》1981,309(1):20-24
Summary The photomineralization test developed by Korte and coworkers has been proposed as a screening test for the evaluation of the photodegradation of chemicals in the OECD Guidelines. On the basis of an automated version using the twin-chamber reactor the test was applied to six different compounds in order to check its interlaboratory reproducibility.Presented at the International Workshop on Test Methods and Assessment Procedures for the Determination of the Photo-chemical Degradation Behaviour of Chemical Substances December 2–4, 1980, Berlin 相似文献
38.
In solving a nonlinear equation by the use of a continuation method one of the crucial problems is the choice of the step sizes. We present a model for the total computational cost of a standard numerical continuation process and solve the problem of optimal step size control for this model. Using the theoretical results as a basis, we develop an adaptive step size algorithm for Newton's method. This procedure is computationally inexpensive and it gives quite satisfactory results compared to some other numerical experiments found in the literature. 相似文献
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D. Richter D.G. Lancaster R.F. Curl W. Neu F.K. Tittel 《Applied physics. B, Lasers and optics》1998,67(3):347-350
3 (PPLN) crystal pumped by two single-frequency diode lasers. A maximum DFG power of 1.6 μW at 3.6 μm was generated with a pump
power of 61.4 mW at 832 nm and a signal power of 41.5 mW at 1083 nm incident on a 19-mm-long PPLN crystal, which corresponds
to a conversion efficiency of 335 μW W-2 cm-1.
Received: 16 June 1998 相似文献