1995 Volume 58 Issue 2 Pages 109-121
We have introduced a tractable formula for the enhancement efficiency of the local electric field, QNF on the basis of Mie theory. For the Ag sphere immersed in the polymer matrix, calculations have been made of QNF as a function of incident wavelength (λ=300-700nm) and sphere diameter (2a=10-400nm). When the incident wavelength is in resonance with surface plasmon mode of the small Ag sphere, QNF has the distinct maximum value. As a typical example of surface-enhanced electromagnetic processes, surface-enhanced Raman scattering (SERS) of silver salt films of high molecular weight carboxylic acids, carboxymethylcellulose (CMCAg+) and alginic acid (ALAg+), photolyzed with UV light has been examined. The Raman intensity of the symmetric COO- stretching vibration of CMCAg+ and ALAg+ has increased with UV irradiation, attained the maximum, and then decreased after prolonged irradiation. A close connection between the Raman intensity and the aggregation state of photolytic silver has been noticed. QNF evaluated for the incident wavelength λ=510nm has been compared with many features of SERS of the CMCAg+ and ALAg+ films. It is suggested that QNF is useful as a practical index for the ability of small metal particles to promote surface-enhanced electromagnetic processes.
