Signs of structural changes in molecules in IR spectra with pulsed heating

We have shown that in slow thermal reactions of complex molecules, effects of nonradiative transitions due to quantum beats between resonant states of the combining molecular structures can be observed in conventional (without high time resolution) IR absorption spectra, as oscillations in the intensities of individual lines. We suggest a method to ensure the required level of coherence for the oscillations in an ensemble of molecules, based on application of pulsed heating to the molecular system. Detection of the qualitatively new effects by traditional IR spectroscopy methods, including their quantitative characteristics, considerably increases the information content of the spectral data obtained and makes it possible to use such highly developed experimental methods to study chemical reactions, including the reaction dynamics. The range of these reactions is quite broad, encompassing both “laboratory” and “natural” (geochemistry, ecology, etc.) processes with characteristic times on the order of minutes or more. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 738–743, November–December, 2007.