Vielma Jason, Leung P T
Department of Physics, Portland State University, P.O. Box 751, Portland, Oregon 97207-0751, USA.
J Chem Phys. 2007 May 21;126(19):194704. doi: 10.1063/1.2734549.
A phenomenological model is implemented to study the decay rates of fluorescing molecules in the vicinity of a metallic nanoparticle, wherein the nonlocal optical response of the particle is accounted for via the hydrodynamic model for the description of the free electrons in the metal. These nonlocal effects are examined for each of the radiative rate and the nonradiative rate of the admolecule, respectively. In addition, the overall fluorescence rate which includes the enhancement ratio for the driving field intensity is also studied. It is found that for particles of very small sizes (<10 nm), the nonlocal effects, in general, lead to significantly greater fluorescence rates and smaller nonradiative decay rates for the admolecules, with the effects on radiative rates depending crucially on the orientation of the molecules. Furthermore, the effects are mostly noticeable for molecules close to the metal particle and in processes where higher multipolar interactions are significant such as those in nonradiative decay processes. Above all, these nonlocal effects can still be observable in the presence of large surface damping imposed on the metallic electrons due to the ultrasmall sizes of these nanoparticles. The relevance of these effects to some of the latest experiments is discussed.
采用一种现象学模型来研究金属纳米颗粒附近荧光分子的衰减率，其中通过描述金属中自由电子的流体动力学模型来考虑颗粒的非局部光学响应。分别针对吸附分子的辐射率和非辐射率研究了这些非局部效应。此外，还研究了包括驱动场强度增强比在内的整体荧光率。研究发现，对于非常小尺寸（<10 nm）的颗粒，一般来说，非局部效应会导致吸附分子的荧光率显著更高，非辐射衰减率更小，对辐射率的影响关键取决于分子的取向。此外，对于靠近金属颗粒的分子以及在更高多极相互作用显著的过程（如非辐射衰减过程）中，这些效应最为明显。最重要的是，由于这些纳米颗粒尺寸超小，在金属电子存在大表面阻尼的情况下，这些非局部效应仍然可以观察到。讨论了这些效应与一些最新实验的相关性。
