Langmuir-Blodgett (LB) films of arachidic acid have been used as spacer layers to control the separation distance between evaporated In and Ag metal island films and LB monolayers of a lightly substituted phthalocyanine. From relative intensity measurements, the distance dependence of the surface-enhanced Raman scattering (SERS) enhancement factor for the phthalocyanine was determined and found to be long range. In addition the magnitude of the enhancement was determined by measurement of the normal Raman intensity of phthalocyanine monolayers deposited directly onto unmetalized substrates. The results are compared with calculations of the enhancement factor based on an electromagnetic field enhancement mechanism. Good quantitative agreement is found between calculation and experiment for both the distance dependence and magnitude of the enhancement. We conclude that our SERS from island films is due to the electromagnetic mechanism and rule out short-range chemical mechanisms.

No abstract

guishing high and low Si/Al ratio zeolites and may be important in studies of zeolites that are chemically or physically altered.Acknowledgment. The support of the National Sci-ence Foundation under Grant CHE 8204417 is gratefully acknowledged. We thank Professor T.

No abstract

No abstract