Ground state-excited state three-photon transition moments: *CCTM

This section describes the calculation of third-order transition moments and strengths. Three photon transition strengths are defined as

$$S^{of}_{ABC,DEF}(\omega_1,\omega_2) = \frac{1}{2} \{ M^{AB... ...}(-\omega_1,-\omega_2) M^{ABC}_{fo}(\omega_1,\omega_2)]^\ast\}$$

where $M^{ABC}_{of}(\omega_1,\omega_2)$ and $M^{ABC}_{fo}(\omega_1,\omega_2)$ are the left and right three photon transition moments, respectively. The methodology is implemented for the CC models CCS, CC2 and CCSD.

.DIPOLE

Calculate the three-photon moments and strengths for all possible combinations of Cartesian components of the electric dipole moment operator (729 combinations).

.OPERAT

READ (LUCMD,'(6A)') LABELA, LABELB, LABELC, LABELD, LABELE, LABELF
DO WHILE (LABELA(1:1).NE.'.' .AND. LABELA(1:1).NE.'*')
READ (LUCMD,'(6A)') LABELA, LABELB, LABELC, LABELD, LABELE, LABELF
ENDDO
Select the sextuples of operator labels for which to calculate the three-photon transition moments. Operator sextuples which do not correspond to symmetry-allowed combinations will be ignored during the calculation.

.PRINT

READ (LUCMD,*) IPRTM
Read print level. Default is 0.

.SELSTA

READ (LUCMD,'(A70)') LABHELP
DO WHILE (LABHELP(1:1).NE.'.' .AND. LABHELP(1:1).NE.'*')
READ (LUCMD,*) IXSYM, IXST, FREQB, FREQC
END DO
Select one or more excited states $f$ (among those specified in *CCEXCI), and the laser frequencies. The symmetry (IXSYM) and state number (IXST) within that symmetry are then given, one pair (IXSYM,IXST) per line. FREQB and FREQC specify the laser frequencies $\omega_1$ and $\omega_2$ (in atomic units).

Default is all states specified in *CCEXCI, and for each state both laser frequencies equal to one third of the excitation energy.

.THIRDF

Set the frequency arguments for the three-photon transition moments equal to one third of the excitation energy of the (chosen) final state $f$. Default, if FREQB,FREQC are not specified in .SELSTA.