Depolarized light scattering in dilute solutions of alkanes: A comparison of the bond additive and interacting atom approximations to the molecular polarizability
The molecular polarizability of a few small alkane (4--10 bond) chains has been represented by (1) an interacting atom model (IAM), wherein the atoms are treated as isotropic point polarizabilities interacting by the dipole tensor; and (2) the bond additive approximation (BAA) in which each bond is assigned an axially symmetric polarizability tensor, and the total molecular polarizability is the sum of the individual bond values. For selected values of the gauche--trans energy difference (0.3 kcal/mole), the calculated mean anisotropy per backbone atom /N increases linearly with N for the IAM and is essentially independent of N in the BAA. Orientational correlation functions have been determined for several second rank tensors characterizing the flexible chains using a modified version of Fixman's Brownian dynamics programs. The orientational correlation functions displayed an effective nonanalytic decay for short times merging into an exponential for long times. Single particle correlation times for the IAM increased more rapidly with N than did those of the BAA. Relaxation of the end-to-end vector (actually its second rank analog) was found to be the slowest process, followed by the IAM and the BAA polarizabilities, and finally the fastest was a local rotational mode.
- Research Organization:
- Department of Chemistry, Yale University, New Haven, Connecticut 06511
- OSTI ID:
- 6534943
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 74:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALKANES
LIGHT SCATTERING
DEPOLARIZATION
MOLECULES
POLARIZABILITY
SOLUTIONS
DISPERSIONS
ELECTRICAL PROPERTIES
HYDROCARBONS
MIXTURES
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SCATTERING
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory