Results 1 - 10 of 1917
Results 1 - 10 of 1917. Search took: 0.026 seconds
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[en] We derive a general expression of the circular dichroism spectra of anisotropically distributed chiral molecules in the polarizability framework by introducing a tensorial rotational strength. Example calculation is carried out on an acridine-substituted Troeger base. It is shown that the circular dichroism is very sensitive to the direction propagation of the light beam
[en] Circular dichroism (CD) of chiral metamaterials is of significant interest for bio-sensing and molecular chemistry applications. In this study, using the gammadion shape as an example, the CD effect of gammadion-shaped chiral metamaterials is investigated. We view the gammadion as four Γ-shaped structures. The CD effect of the gammadion is induced by the conductive and magneto-inductive coupling between the weak and strong magnetic fields of the Γ-shaped structures. A large CD effect can be achieved because the magnetic fields excited by the conductive and magneto-inductive coupling show the same and opposing directions for right- and left-handed circular-polarized waves, respectively. This allows analysis of the origin of plasmonic modes in the CD spectrum. We can change the CD effect by changing the conductive and magneto-inductive coupling of the magnetic fields. The CD properties can be tuned by changing either the number of Γ-shaped structures or the layer spacing. These results may guide the design of chiral metamaterials at terahertz frequencies for achieving large CD effects. Furthermore, this approach can be applied to other complex planar structures to gain further insight on the origin of CD modes. (paper)
[en] Highlights: • First report of chlorofullerenes’ magnetic circular dichroism spectra. • Advanced time-dependent density functional theory computations are used and analyzed as a basis for spectral interpretation. • The spectra are specific for each studied molecule and thus useful in material studies of fullerene derivatives. Magnetic circular dichroism (MCD) spectra of C60Cl6, C70Cl10 and C60Cl24 were measured and interpreted using a sum-over-state (SOS) protocol exploiting time dependent density functional theory (TDDFT). Unlike for plain absorption, the MCD spectra exhibited easily recognizable features specific for each chlorinated molecule and appear as a useful tool for chlorofullerene identification. MCD spectrum of C60Cl24 was below 400 nm partially obscured due to scattering and low solubility. In all cases a finer vibrational structure of the electronic bands was observed at longer wavelengths. The TDDFT simulations provided a reasonable basis for interpretation of the most prominent spectral features.
[en] The electronic as well as magnetic properties of GaxFe1-x films were studied by soft x-ray measurements. Using x-ray magnetic circular dichroism the Fe majority-spin band was found to be completely filled for x ∼ 0.3. With further enhanced Ga content, the Fe moment as well as the angular dependence of the x-ray magnetic linear dichroism decrease strongly, which we attribute to the formation of D03 precipitates. Moreover, the magnetocrystalline anisotropy drops significantly.
[en] An application of a digital storage oscilloscope for nanosecond time-resolved spectroscopic measurements is demonstrated in the range from the single-photon region to the multi-photon region. In comparison to the time-correlated single photon counting (TCSPC) method, the measurement setup can be greatly simplified by averaging the signals measured by the oscilloscope. Moreover, the multi-photon events of the fluorescence emissions can be tracked by this simple setup although there still exist some disadvantages in the dynamic range of the signal due to radio frequency noise, and the temporal response of the photo-multiplier tube. This method can simplify time-resolved optical measurements in the nanosecond range, such as fluorescence decay and time-of-flight measurements of diffusing light. Thus, this simple method will be applicable in many clinical and industrial uses. (note)