Operator App

This has been called the Tamm-Dancoff approximation [104] and corresponds to singly excited Cl in the reference Hartree-Fock orbitals. Adding de-excitation operators to obtain the full operator App (ft)) one obtains the random-phase... 

The beta spin operator app corresponds to the component M = b since it removes an electron with spin projection — thereby increasing the spin projection of the system. 

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