where are the matrix elements of the perturbing operator. A similar expression is obtained for the ``left'' transition moments. The ``left'' and ``right'' transition moments are then combined to yield the transition strength

As for the ground state transitions, only the transition strengths

The single-substitution parts of the transition Lagrangian
multipliers
are saved in files named
`CCNE0-`

*s*`--`

*m*`-`

*xxx*.

To obtain the transition strengths for excitations between excited states the keyword
`tmexc`

must be added to the data group `$excitations`. Additionally, the initial and final states must be given in the same line; else the input is same as for the
calculation of excitation energies and first-order properties:

$ricc2 cc2 $excitations irrep=a1 nexc=2 irrep=a2 nexc=2 tmexc istates=(a1 1) fstates=all operators=diplen