Correlation Spectroscopy

Today, the interpretation of spectroscopic data with the aid of time -dependent autocorrelation functions (acfs) has found widespread application to molecules in solids, liquids and dense gases. In this paper the two dominant relaxation processes influencing the acfs of rotational and vibrational relaxation are reviewed. The influence of Coriolis coupling on the rotational acfs of degenerate vibrations is emphasized. Experimental acfs are discussed for the rotational relaxation of HC1 in tetrachlorides, OHand ODions in single crystals of alkalihalides, gaseous chloroform and of methanes in liquid argon as well as for intramoleculer vibrational relaxation in the metal carbonyls Cr(C0)6, Mo(CO )6 and W(CO)6.