We call this ISP analysis. To carry out these two analyses, we employ Thiel's benchmark set and systematically investigate a large number of singlet and triplet vertical excitation energies in 28 small organic compounds. The geometries are taken from the original work and correspond to MP2 optimized structures, in combination with the 6-31G* 62,63 basis set. The selection of active spaces and the number of states included in the SA-CASSCF optimization follows closely that of the original reference. The starting point for both analyses is the calculation of 311 singlet and triplet excitation energies using the MS-CASPT2 method (and its diagonal counterpart, MS-CASPT2D), in association with the TZVP basis set and the atomic compact Cholesky decomposition of the two-electron integrals (using the default threshold value of 10 -4 E h ). Here, the IPEA shift 41 was set to zero and the unmodified generalized Fock operator was used (i.e. no g 1 zeroth-order Hamiltonian 59 ).