银原子团簇共振散射光谱的密度矩阵研究

Resonance Scattering Spectra for Silver Clusters by Density Matrix Procedure

关键词:  银原子团簇  非线性共振散射  密度矩阵法

Key words:  silver clusters  nonlinear resonance scattering  density matrix procedure

摘要:

以银原子团簇(主)共振散射峰作为共振散射光谱分布理论研究模型,采用密度矩阵法研究液相银原子团簇(主)共振散射峰(7.06×10¹⁴ Hz,425 nm)和1/2分频共振散射峰(1/2×7.06×10¹⁴ Hz,850 nm)的频率和强度分布。银原子团簇(r=12 nm)溶液呈黄色,在415 nm处有1个吸收峰;在470 nm处产生吸收谷,在485 nm处产生吸收峰,最大共振散射波长为425 nm(×10¹⁴ Hz)。当λ_ex=425nm时,在425nm处产生1个主共振峰,在850nm(1/2×10¹⁴ Hz)处产生1个1/2分频共振峰。对于不同浓度的银原子团簇(0~1.0×10^-5 mol/LAg),两散射峰的半峰宽度之比(△ λ)₄₂₅/(△ λ)₈₅₀=2/3,其散射光强度之比I_425/425/I_425/850≈3/1。在理想条件(真空)下,理论推导出共振散射光中心峰带与两边峰带谱线的强度比为1/3;中心峰与边峰的高度比为3:1;边峰宽与中心峰宽之比为3:2。

Abstract:

The main resonance scattering peak was used as the model for studying the distribution of resonance scattering spectra. The density matrix procedure was employed to calculate the frequency and intensity of main resonance scattering peak at 7.06×10¹⁴ Hz(425nm) and a 1/2 fraction frequency resonance scattering peak at 1/2×7.06×10¹⁴ Hz(850 nm) of silver clusters. Silver cluster solution is yellow, and produces a absorption peak at 415 nm, and a absorption valley at 470 nm and a absorption peak again at 485 nm. The wavelength of the largest resonance scattering spectra is 425 nm(×10¹⁴ Hz).When λ_ex=425 nm, there is a main resonance scattering peak at 425 nm, a 1/2 fraction frequency resonance scattering peak at 850 nm. For silver clusters of concentrations from zero to 10^-5 mol/L Ag, the ratio of half-width of peak of two scattering peaks is 2 to 3;and ratio of their intensity (I_425/425/I_425/850)≈3/1.Under ideal conditions(vacuum),it is calculated that the ratios of intensity,peak height and peak width of middle peak to side peak are 1 to 3,3 to 1 and 3 to 2, respectively.