Packing and Symmetry of Ultrathin Films

Films can be divided into three classes—isonopic, uniaxial, and biaxial—depending on the form of their permittivity tensor s (1.1.2°). For isotropic films, the three principal values of the permittivity tensor are equal, i = 62 = s-, and there is no preferred orientation within the film. The permittivity tensor of a uniaxial film has two different principal values, one that describes the propagation of radiation in the film plane and another that is perpendicular to the film plane, so that = Sy s. For a biaxial film all of the principal values of the permittivity tensor are different, so that Ex By For crystalline films with triclinic 

1458vw Scissor of CH2 group next to a gauche bond 

Source Reprinted, by permission, from S. J. Lee and K. Kim, Vibrational Spectrosc. 18, 187 (1998), p. 192, Table 2. Copyright 1998 Elsevier Science B.V. 

1 To characterize arrangement of the adsorbate head groups on the substrate surface the lUPAC nomenclature for two dimensional Bravais cells is used [A. M. Bradshaw and N. V. Richardson, Pure Appl. Chem. 68, 457 (1996)]. 

The TDM of the higher frequency component (1472-1473 cm ) of the 5scisCH2 mode of hydrocarbon chains packed in the orthorhombic subcell is directed along the a-axis of the subcell, while the lower frequency component 

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