Wave function phase-isolated, time-dependent

A different analysis applies to the LR approach (in either Tamm-Dancoff, Random Phase Approximation, or Time-dependent DFT version) where the excitation energies are directly determined as singularities of the frequency-dependent linear response functions of the solvated molecule in the ground state, and thus avoiding explicit calculation of the excited state wave function. In this case, the iterative scheme of the SS approaches is no longer necessary, and the whole spectrum of excitation energies can be obtained in a single run as for isolated systems. 

It is a real quantity, which follows from the fact that the time-dependent Schrodinger equation conserves the norm of the wave function. The phase-isolated wave... 

Let us consider the time-dependent wave function (t) > expressed in the phase isolated form... 

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