Ground state-excited state transition moments: *CCLRSD

In the *CCLRSD section the input that is specific for coupled cluster response calculation of ground state-excited state electronic transition properties is read in. This section includes for example calculation of oscillator strength etc. The transition properties are implemented for the models CCS, CC2 and CCSD (singlet states only). The theoretical background for the implementation is detailed in Ref.
citeChristiansen:CCLR,Christiansen:QEL. This section *CCLRSD has to be used in connection with *CCEXCI for the calculation of excited states.

.DIPOLE

Calculate the ground state-excited state dipole (length) transition properties including the oscillator strength.

.DIPVEL

Calculate the ground state-excited state dipole-velocity transition properties including the oscillator strength in the dipole-velocity form. (The dipole length form is recommended for standard calculations).

.NO2N+1

Use an alternative, and normally less efficient, formulation for calculation the transition matrix elements (involving solution of response equations for all operators instead of solving for the so-called $M$ vectors which is the default).

.OPERAT

READ (LUCMD,'(2A8)') LABELA, LABELB
Read pairs of operator labels for which the residue of the linear response function is desired. Can be used to calculate the transition property for a given operator by specifying that operator twice. The operator can be any of the one-electron operators for which integrals are available in the **INTEGRALS input part.

.SELEXC

READ(LUCMD,*) IXSYM,IXST
Select for which excited states the calculation of transition properties are carried. The default is all states according to the *CCEXCI input section (the program takes into account symmetry). For calculating selected states only, provide a list of symmetry and state numbers (order after increasing energy in each symmetry class). This list is read until next input label is found.