Coupling tetratomic molecules

Summary of interbond couplings in linear tetratomic molecules... 

The types of couplings needed to describe accurately vibrational spectra of linear tetratomic molecules are summarized in Table 5.4. In most molecules, only the C, M, and C operators are needed. The S and Cf, operators are necessary only in some exceptional cases. 

With the local basis, we are ready to construct a triatomic-like Hamiltonian operator where most of the physically relevant interactions should be either diagonal or in the nondiagonal form of the Majorana operator. This is a direct consequence of our choice for the coupling scheme (1 -I- 2) -f- 3, which is, in fact, done to favor interactions of the type (H-2). So for a linear tetratomic molecule we write the following Hamiltonian operator ... 

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