Search results for " Optics"
showing 10 items of 5880 documents
Crystallization of chiral molecular compounds: what can be learned from the Cambridge Structural Database?
2020
A detailed study on chiral compound structures found in the Cambridge Structural Database (CSD) is presented. Solvates, salts and co-crystals have intentionally been excluded, in order to focus on the most basic structures of single enantiomers, scalemates and racemates. Similarity between the latter and structures of achiral monomolecular compounds has been established and utilized to arrive at important conclusions about crystallization of chiral compounds. For example, the fundamental phenomenon of conglomerate formation and, in particular, their frequency of occurrence is addressed. In addition, rarely occurring kryptoracemates and scalemic compounds (anomalous racemates) are discussed.…
Optical calibration of a multispectral imaging system based on interference filters
2005
We present a new approach to optically calibrate a multispectral imaging system based on interference filters. Such a system typically suffers from some blurring of its channel images. Because the effectiveness of spectrum reconstruction depends heavily on the quality of the acquired channel images, and because this blurring negatively affects them, a method for deblurring and denoising them is required. The blur is modeled as a uniform intensity distribution within a circular disk. It allows us to characterize, quantitatively, the degradation for each channel image. In terms of global reduction of the blur, it consists of the choice of the best channel for the focus adjustment according to…
Dipolar coupling of nanoparticle-molecule assemblies: An efficient approach for studying strong coupling
2021
Strong light-matter interactions facilitate not only emerging applications in quantum and non-linear optics but also modifications of materials properties. In particular the latter possibility has spurred the development of advanced theoretical techniques that can accurately capture both quantum optical and quantum chemical degrees of freedom. These methods are, however, computationally very demanding, which limits their application range. Here, we demonstrate that the optical spectra of nanoparticle-molecule assemblies, including strong coupling effects, can be predicted with good accuracy using a subsystem approach, in which the response functions of the different units are coupled only a…
Size-Dependent Structural Evolution and Chemical Reactivity of Gold Clusters
2006
Ground-state structures and other experimentally relevant isomers of Au(15) (-) to Au(24) (-) clusters are determined through joint first-principles density functional theory and photoelectron spectroscopy measurements. Subsequent calculations of molecular O(2) adsorption to the optimal cluster structures reveal a size-dependent reactivity pattern that agrees well with earlier experiments. A detailed analysis of the underlying electronic structure shows that the chemical reactivity of the gold cluster anions can be elucidated in terms of a partial-jellium picture, where delocalized electrons occupying electronic shells move over the ionic skeleton, whose geometric structure is strongly infl…
B-parameters for ΔS=2 supersymmetric operators
1998
We present a calculation of the matrix elements of the most general set of DeltaS=2 dimension-six four-fermion operators. The values of the matrix elements are given in terms of the corresponding B-parameters. Our results can be used in many phenomenological applications, since the operators considered here give important contributions to K^0--K^0bar mixing in several extensions of the Standard Model (supersymmetry, left-right symmetric models, multi-Higgs models etc.). The determination of the matrix elements improves the accuracy of the phenomenological analyses intended to put bounds on basic parameters of the different models, as for example the pattern of the sfermion mass matrices. Th…
Dissipation of vibronic energy in a dimer
1992
Abstract The density matrix theory is used for the study of the dissipative quantum dynamics of electron transfer in a dimer. The vibrational modes of the dimer are divided into a single interaction coordinate coupling to the transfered electron and the remaining modes which form a dissipative environment. To correlate the dissipative dynamics with the exact eigenlevels computed for the model system without dissipative environment we analyse the time dependence of the expectation value of the number of vibrational quanta. We analyse the renormalisation of the eigenvalues due to the damping and the relaxation of an excitation into these states.
Integral-geometrical consideration of density matrices
1995
The ensemble N-representability problem for the k-th order reduced density matrix (k-RDM) as well as the problem of reconstruction of the N-particle system density matrices (N-DM) from a given k-RDM are studied. The spatial parts of the k-RDM expansion in terms of spin tensorial operators {Theta}{sub {lambda}} are represented using particular values (at specially chosen {Xi} = {Xi}{sub o}) of the Radon transform D{sub N{lambda}} D{sub N{lambda}}({Xi}) of the N-DM spatial parts (or their sums) D{sub N{lambda}}({chi}{prime}{vert_bar}{chi}{double_prime}) (here, {Xi} is a d-plane in the n-space {Re}{double_prime} of {chi} = ({chi}{prime}, {chi}{double_prime}), with n = 6N, d = 3(N - k), {chi}{p…
Anomalous d-like surface resonances on Mo(110) analyzed by time-of-flight momentum microscopy.
2015
The electronic surface states on Mo(110) have been investigated using time-of-flight momentum microscopy with synchrotron radiation (hν=35 eV). This novel angle-resolved photoemission approach yields a simultaneous acquisition of the E-vs-k spectral function in the full surface Brillouin zone and several eV energy interval. (kx,ky,EB)-maps with 3.4 A(-1) diameter reveal a rich structure of d-like surface resonances in the spin-orbit induced partial band gap. Calculations using the one-step model in its density matrix formulation predict an anomalous state with Dirac-like signature and Rashba spin texture crossing the bandgap at Γ¯ and EB=1.2 eV. The experiment shows that the linear dispersi…
Remote Modification of Bidentate Phosphane Ligands Controlling the Photonic Properties in Their Complexes: Enhanced Performance of [Cu(RN‐xantphos)(N…
2020
A series of copper(I) complexes of the type [Cu(HN-xantphos)(N^N)][PF6] and [Cu(BnN-xantphos)(N^N)][PF6], in which N^N = bpy, Mebpy and Me2bpy, HN-xantphos = 4,6-bis(diphenylphosphanyl)-10H-phenoxazine and BnN-xantphos = 10-benzyl-4,6-bis(diphenylphosphanyl)-10H-phenoxazine is described. The single crystal structures of [Cu(HN-xantphos)(Mebpy)][PF6] and [Cu(BnN-xantphos)(Me2bpy)][PF6] confirm the presence of N^N and P^P chelating ligands with the copper(I) atoms in distorted coordination environments. Solution electrochemical and photophysical properties of the BnN-xantphos-containing compounds (for which the highest-occupied molecular orbital is located on the phenoxazine moiety) are repor…
Entanglement dynamics of two independent cavity-embedded quantum dots
2010
We investigate the dynamical behavior of entanglement in a system made by two solid-state emitters, as two quantum dots, embedded in two separated micro-cavities. In these solid-state systems, in addition to the coupling with the cavity mode, the emitter is coupled to a continuum of leaky modes providing additional losses and it is also subject to a phonon-induced pure dephasing mechanism. We model this physical configuration as a multipartite system composed by two independent parts each containing a qubit embedded in a single-mode cavity, exposed to cavity losses, spontaneous emission and pure dephasing. We study the time evolution of entanglement of this multipartite open system finally …