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81.
82.
Fluorescence resonance energy transfer (FRET) is a popular tool to study equilibrium and dynamical properties of polymers
and biopolymers in condensed phases and is now widely used in conjunction with single molecule spectroscopy. In the data analysis,
one usually employs the F?rster expression which predicts (l/R
6) distance dependence of the energy transfer rate. However, critical analysis shows that this expression can be of rather limited validity in many cases. We demonstrate this by explicitly considering a donor-acceptor system,
polyfluorene (PF6)-tetraphenylporphyrin (TPP), where the size of both donor and acceptor is comparable to the distance separating them. In
such cases, one may expect much weaker distance (as l/R
2 or even weaker) dependence. We have also considered the case of energy transfer from a dye to a nanoparticle. Here we find
l/R
4 distance dependence at large separations, completely different from F?rster. We also discuss recent application of FRET to
study polymer conformational dynamics.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
83.
84.
85.
The total energy distribution (TED) of field-emitted electrons from an adsorbate-covered metal surface is studied within the framework of the Anderson Hamiltonian, but taking overcompleteness of states into account. The correct asymptotic behavior of the adsorbate wavefunction, postulated in the previous work, is now established, and a numerical correction factor (~15) to the adsorbate induced current density is obtained. 相似文献
86.
A new expression is derived for the differential reflectance from an arbitrary metal surface, with chemisorbed impurities, using -polarized radiation. The use of the result, which depends entirely on the dielectric response tensor of the system, to study experimental Surface Reflectance data is discussed. 相似文献
87.
In this note we determine the dimensions of the binary codes spanned by the lines or by the point neighborhoods in the generalized quadrangle Sp(4, q) and its dual O(5, q), where q is odd. Several more general results are given. As a side result we find that if a square generalized quadrangle of odd order has an antiregular point, then all of its points are antiregular.On leave from the Indian Statistical Institute, Calcutta; research supported by a grant from NWO. 相似文献
88.
89.
A self-consistent mode-coupling theory is presented for the viscosity of solutions of charged rodlike polymers. The static structure factor used in the theory is obtained from polymer integral equation theory; the Debye-Huckel approximation is inadequate even at low concentrations. The theory predicts a nonmonotonic dependence of the reduced excess viscosity eta(R) on concentration from the behavior of the static structure factor in polyelectrolyte solutions. The theory predicts that the peak in eta(R) occurs at concentrations slightly lower than the overlap threshold concentration, c*. The peak height increases dramatically with increasing molecular weight and decreases with increased concentrations of added salt. The position of the peak, as a function of concentration divided by c*, is independent of salt concentration or molecular weight. The predictions can be tested experimentally. 相似文献
90.
A self-consistent microscopic theory is developed to understand the anomalously weak concentration dependence of ionic self-diffusion coefficient D(ion) in electrolyte solutions. The self-consistent equations are solved by using the mean spherical approximation expressions of the static pair correlation functions for unequal sizes. The results are in excellent agreement both with the known experimental results for many binary electrolytes and also with the new Brownian dynamics simulation results. The calculated velocity time correlation functions also show quantitative agreement with simulations. The theory also explains the reason for observing different D(ion) in recent NMR and neutron scattering experiments. 相似文献