ABSTRACT
In which c is the velocity of light (3 x 1010 em s-1), and v is the wavenumber (frequency) at which the molecule has to vibrate. For two molecules of two different masses, one can write vJ!v2 = (J.12/J.1 1) 112 , considering k is the same in both cases. If the OH group is treated as a simple diatomic harmonic oscillator, thus for OH and OD (D =deuterium) we have (f.loo/J.loH)1=(16j9x17j16)!= (17 /9)112 = 1.37, which means that the ratio between OH and OD frequencies is 1.37. Subjecting silica to 0 20 and recording the infrared spectrum revealed the shift of the originally present band at 3750 cm-1 (attributed to freely vibrating surface OH group) to appear at 2750 cm-1. The ratio 3750/2750 = 1.36 agrees well with the calculated one. This observation has led to the conclusion that the isotopic band shift is due to exchange of the proton of the OH group with D of 0 20, and for this to occur the OH group has to be located on the surface as the nature of the exchange does not permit OH groups not on the surface to come into play. The use of infrared spectroscopy in combination with adsorption of different species was the subject of a very large body of research devoted either to characterizing the surface of different silicas, or to studying the activity of the functional groups differently distributed on the surface of silica. Computer-interfaced equipment made the technique invaluable in these respects. The work undertaken by Prof. Morrow and Prof. Davydov highlights this area.
