Atomic Polar Tensors — Examples of Application

In this section we will present examples of how atomic polar tensors are derived from experimental infrared intensity data for three molecules — the non-polar molecule of ethane and for CH3CI and H2O, two molecules that possess a permanent dipole moment. Data for die last two molecules were also used to illustrate the valence-tqitical scheme. 

Definitions of internal coordinates, bond directions, Cartesian reference system and numbering of atoms for ethane. 

Expeiimental data, definitions of coordinates, molecular geomehy data, and L and P3 matrices for med l chloride are given in section 3.3. The calculated atomic polar tensor matrix is given below (in units of D A ) [124]. 

Px is a sum of two terms — vibrational polar tensor (PgBg) and rotational polar tensor (PpP). The rotational polar tensor is evaluated using an equilibrium dipole moment value of -1.87 D [34]. The PsBs and PpP matrices are given below. 

Coordinate definitions, Lg and P matrices for H2O used in evaluating the atomic polar tensor elements are as given in section 3.3. With the aid of relation (4.14) die Pg matrix is transformed into vibrational polar tensor, while the rotational polar tensor is calculated using a permanent dipole moment value of-1.85 D [34]. The two submatrices obtained are as follows (in units of D A l)  

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