Buried Metal Layer Substrates BML-IRRAS

Although IRRAS is a well-established method for studying monolayers on transparent substrates, its sensitivity is almost an order of magnitude lower than on metals. At the same time, transparent IRRAS offers an important advantage that p- and j-polarized spectra of the film can be measured, which is extremely valuable for orientational studies (Section 3.11.5). One can combine the advantages of metalhc and transparent IRRAS by using a complex-substrate transparent layer on a metal (Fig. 2.16), rather than a single-substance substrate. The upper transparent layer, which imitates the surface chemistry of a bulk transparent substrate, is dubbed a buffer or interference layer. The technique that involves such a buffer layer-metal substrate is known as buried metal layer (BML)-IRRAS or interference underlayer IRRAS. 

The radiation reflected from a two-layer system can be represented as a superposition of the components h, I2, , In, which arise at the interface of each different layer (Fig. 2.16). These components are functions of the optical constants and thicknesses of the upper and lower layers ( 2, fe, 2 and 3, k, d ), the optical constants of the metal ( 4, 4), and the angle of incidence of the light, P. These functions can be calculated with the Fresnel formulas as described in Section 1.7. In the computations [62], values of the optical constants of the upper 

OPTIMUM CONDITIONS FOR RECORDING INFRARED SPECTRA OF ULTRATHIN FILMS 

It is also of interest to study the effect of the absorption coefficient 3 of the buffer layer on AR/R. For this, calculations of R and AR/R were performed for the VasCH2 band of a monolayer 2.5 nm thick of a long-chain surfactant described by vq = 2920 cm oo = 2.22, S = 0.004, and y = 10 cm . The absorption index kj, of the buffer layer 750 nm thick with 3 = 1.4 was varied 

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