Wu Yanpeng, Nordlander Peter
Department of Physics and Astronomy, Rice University, MS 61, Houston, TX 77251-1892, USA.
J Chem Phys. 2006 Sep 28;125(12):124708. doi: 10.1063/1.2352750.
We apply the plasmon hybridization method to a nanoshell with a nonconcentric (offset) core and investigate how the energy and excitation cross section of the plasmon modes depend on the offset distance D of the inner core from the nanoshell center. A two-center spherical coordinate system is used for mathematical convenience. It is shown that the presence of an offset core shifts the plasmon energies and makes higher multipolar nanoshell plasmons dipole active and visible in the optical spectrum. The dependence of the plasmon shifts on D is weak for small offsets but strong for large offsets. The polarization dependence of the optical absorption spectra is found to be relatively weak. The electromagnetic field enhancements are shown to be much larger than on a concentric nanoshell. The results agree very well with results from finite difference time domain simulations.
我们将等离激元杂交方法应用于具有非同心（偏心）内核的纳米壳，并研究等离激元模式的能量和激发截面如何依赖于内核对纳米壳中心的偏移距离D。为了数学上的便利，使用了双中心球坐标系。结果表明，偏心内核的存在会使等离激元能量发生偏移，并使更高阶多极纳米壳等离激元具有偶极活性，且在光谱中可见。对于小偏移量，等离激元偏移对D的依赖性较弱，但对于大偏移量则较强。发现光吸收光谱的偏振依赖性相对较弱。结果表明，电磁场增强比同心纳米壳上的增强要大得多。这些结果与有限差分时域模拟的结果非常吻合。
