RAMAN-STUDY OF VIBRATIONAL DEPHASING IN HYDROGEN-BONDED BINARY AND TERNARY COMPLEXES OF C6H5CL AND METHANOL

The shifts and linewidth changes of three vibrational modes of C6H5Cl were studied in hydrogen-bonded binary mixtures C6H5Cl+ CH3OH at vario us mole fractions of C6H5Cl, C = 0.05, 0.1, 0.2, 0.3, 0.5, 0.7 and 0.9 . The study reveals that the phenomena of motional narrowing and diffu sion play simultaneous roles in the dephasing of the ring breathing an d trigonal bending modes at similar to 1000 and similar to 1024 cm(-1) , respectively. Minima at C=0.7 and 0.2 in the Gamma(L) versus C plot are explained by the formation of hydrogen-bonded dimer, C6H5Cl ... HO CH3, and trimer, C6H5Cl ...(HOCH3)(2), complexes. The dephasing of a t hird mode at similar to 700 cm(-1) is explained using the indirect dep hasing model of Fischer-Laubereau. (C) 1998 Elsevier Science B.V. All rights reserved.