\newcommand{\Pop}{6-31+G(d)} \newcommand{\AVDZ}{aug-cc-pVDZ} \newcommand{\AVTZ}{aug-cc-pVTZ} \newcommand{\DAVTZ}{d-aug-cc-pVTZ} \newcommand{\AVQZ}{aug-cc-pVQZ} \newcommand{\DAVQZ}{d-aug-cc-pVQZ} \newcommand{\TAVQZ}{t-aug-cc-pVQZ} \newcommand{\AVFZ}{aug-cc-pV5Z} \newcommand{\DAVFZ}{d-aug-cc-pV5Z} \newcommand{\ra}{\rightarrow} \newcommand{\pis}{\pi^\star} \newcommand{\si}{\sigma} \newcommand{\sis}{\sigma^\star} \newcommand{\nO}{n_\text{O}} \newcommand{\nN}{n_\text{N}} \newcommand{\piCC}{\pi_{\ce{CC}}} \newcommand{\pisCC}{\pi_{\ce{CC}}^\star} \newcommand{\piCO}{\pi_{\ce{CO}}} \newcommand{\pisCO}{\pi_{\ce{CO}}^\star} \newcommand{\siCC}{\si_{\ce{CC}}} \newcommand{\sisCC}{\si_{\ce{CC}}^\star} \newcommand{\siCO}{\si_{\ce{CO}}} \newcommand{\sisCO}{\si_{\ce{CO}}^\star} \begin{dfbOptions} \format{DoubleColumn} \suffix{double} \end{dfbOptions} \begin{tabular} Molecule & Transition & Method & \multicolumn{4}{c}{Basis set} & \multicolumn{1}{c}{Lit.} \\ & & &\multicolumn{1}{c}{6-31+G(d)}& \multicolumn{1}{c}{\AVDZ}& \multicolumn{1}{c}{\AVTZ}& \multicolumn{1}{c}{\AVQZ} &\\ Acrolein & $1\,^1A^\prime \ra 3\,^1A^\prime$ & FCI & 8.00(3) & & & & 8.16$^a$ \\ & $\pi,\pi \ra \pis,\pis$ & CC3($\%T_1$)& 8.21(73\%) & 8.11(75\%) & 8.08(75\%) & & \\ & & CASPT2 & 7.93 & 7.93 & 7.85 & 7.84 & \\ & & MS-CASPT2 & 8.36 & 8.30 & 8.28 & 8.30 & \\ & & XMS-CASPT2 & 8.18 & 8.12 & 8.07 & 8.07 & \\ & & PC-NEVPT2 & 7.91 & 7.93 & 7.85 & 7.84 & \\ & & SC-NEVPT2 & 8.08 & 8.09 & 8.01 & 8.00 & \\ \\ Benzene & $1\,^1A_{1g} \ra 1\,^1E_{2g}$ & FCI & 8.40(3) & & & & 8.41$^b$ \\ & $\pi,\pi \ra \pis,\pis$ & CCSDT & 8.42 & 8.38 & & & \\ & & CC3($\%T_1$)& 8.50(72\%) & 8.44(72\%) & 8.38(73\%) & & \\ & & CASPT2 & 8.43 & 8.40 & 8.34 & 8.34 & \\ & & PC-NEVPT2 & 8.58 & 8.56 & 8.51 & 8.52 & \\ & & SC-NEVPT2 & 8.62 & 8.61 & 8.56 & 8.56 & \\ \\ & $1\,^1A_{1g} \ra 2\,^1A_{1g}$ & CASPT2 & 10.54 & 10.38 & 10.28 & 10.27 & 10.20$^c$ \\ & $\pi,\pi \ra \pis,\pis$ & MS-CASPT2 & 11.08 & 11.00 & 10.96 & 10.97 & \\ & & XMS-CASPT2 & 10.77 & 10.64 & 10.55 & 10.54 & \\ & & PC-NEVPT2 & 10.35 & 10.18 & 10.00 & & \\ & & SC-NEVPT2 & 10.63 & 10.48 & 10.38 & 10.36 & \\ \\ Beryllium & $1\,^1S \ra 1\,^1D$ & FCI & 8.04(0) & 7.22(0) & 7.15(0) & 7.11(0) & 7.06$^d$ \\ & $2s,2s \ra 2p,2p$ & CCSDTQ & 8.04 & 7.23 & 7.15 & 7.11 & \\ & & CCSDT & 8.04 & 7.22 & 7.15 & 7.11 & \\ & & CC3($\%T_1$)& 8.04(2\%) & 7.23(29\%) & 7.17(32\%) & 7.12(34\%) & \\ & & CASPT2 & 8.02 & 7.21 & 7.12 & 7.10 & \\ & & NEVPT2 & 8.01 & 7.20 & 7.11 & 7.10 & \\ \\ Butadiene & $1\,^1A_g \ra 2\,^1A_g$ & FCI & 6.55(3) & 6.51(12) & & & 6.55$^e$, 6.39$^f$, 6.58$^g$ \\ & $\pi,\pi \ra \pi,\pi$ & CCSDT & 6.63 & 6.59 & & & \\ & & CC3($\%T_1$)& 6.73(74\%) & 6.68(76\%) & 6.67(75\%) & 6.67(75\%) & \\ & & CASPT2 & 6.80 & 6.78 & 6.74 & 6.75 & \\ & & PC-NEVPT2 & 6.75 & 6.74 & 6.70 & 6.70 & \\ & & SC-NEVPT2 & 6.83 & 6.82 & 6.78 & 6.78 & \\ \\ Carbon dimer & $1\,^1\Sigma_g^+ \ra 1\,^1\Delta_g$ & FCI & 2.29(0) & 2.21(0) & 2.09(0) & 2.06(0) & 2.11$^h$ \\ & $\pi,\pi \ra \si,\si$ & CCSDTQP & 2.29 & 2.21 & & & \\ & & CCSDTQ & 2.32 & 2.24 & 2.13 & & \\ & & CCSDT & 2.69 & 2.63 & 2.57 & 2.57 & \\ & & CC3($\%T_1$)& 3.10(0\%) & 3.11(0\%) & 3.05(0\%) & 3.03(0\%) & \\ & & CASPT2 & 2.40 & 2.36 & 2.24 & 2.21 & \\ & & PC-NEVPT2 & 2.33 & 2.26 & 2.12 & 2.08 & \\ & & SC-NEVPT2 & 2.35 & 2.28 & 2.14 & 2.11 & \\ \\ & $1\,^1\Sigma_g^+ \ra 2\,^1\Sigma_g^+$ & FCI & 2.51(0) & 2.50(0) & 2.42(0) & 2.40(0) & 2.43$^h$, 2.46$^i$ \\ & $\pi,\pi \ra \si,\si$ & CCSDTQP & 2.51 & 2.50 & & & \\ & & CCSDTQ & 2.52 & 2.52 & 2.45 & & \\ & & CCSDT & 2.86 & 2.87 & 2.86 & 2.87 & \\ & & CC3($\%T_1$)& 3.23(0\%) & 3.28(0\%) & 3.26(0\%) & 3.24(0\%) & \\ & & CASPT2 & 2.62 & 2.65 & 2.53 & 2.50 & \\ & & PC-NEVPT2 & 2.54 & 2.54 & 2.42 & 2.39 & \\ & & SC-NEVPT2 & 2.58 & 2.60 & 2.48 & 2.44 & \\ \\ Carbon trimer & $1\,^1\Sigma_g^+ \ra 1\,^1\Delta_g$ & FCI & 5.27(1) & 5.21(0) & 5.22(4) & 5.23(5) & \\ & $\pi,\pi \ra \si,\si$ & CCSDTQ & 5.35 & 5.31 & & & \\ & & CCSDT & 5.85 & 5.82 & 5.90 & 5.92 & \\ & & CC3($\%T_1$)& 6.65(0\%) & 6.65(0\%) & 6.68(1\%) & 6.66(1\%) & \\ & & CASPT2 & 5.13 & 5.06 & 5.08 & 5.08 & \\ & & PC-NEVPT2 & 5.26 & 5.24 & 5.25 & 5.26 & \\ & & SC-NEVPT2 & 5.21 & 5.19 & 5.21 & 5.22 & \\ \\ & $1\,^1\Sigma_g^+ \ra 2\,^1\Sigma_g^+$ & FCI & 5.93(1) & 5.88(0) & 5.91(2) & 5.86(1) & \\ & $\pi,\pi \ra \si,\si$ & CCSDTQ & 6.02 & 6.00 & & & \\ & & CCSDT & 6.52 & 6.49 & 6.57 & 6.58 & \\ & & CC3($\%T_1$)& 7.20(1\%) & 7.20(1\%) & 7.24(1\%) & 7.22(1\%) & \\ & & CASPT2 & 5.86 & 5.81 & 5.82 & 5.82 & \\ & & PC-NEVPT2 & 5.97 & 5.97 & 5.99 & 5.99 & \\ & & SC-NEVPT2 & 5.98 & 5.97 & 5.99 & 6.00 & \\ \\ Ethylene & $1\,^1A_g \ra 2\,^1A_g$ & FCI & 13.38(6) & 13.07(1) & 12.92(6) & & 12.15$^j$ \\ & $\pi,\pi \ra \pis,\pis$ & CCSDTQP & 13.39 & & & & \\ & & CCSDTQ & 13.39 & 13.07 & & & \\ & & CCSDT & 13.50 & 13.20 & & & \\ & & CC3($\%T_1$)& 13.82(4\%) & 13.57(15\%) & 13.42(20\%) & 13.06(61\%) & \\ & & CASPT2 & 13.49 & 13.23 & 13.17 & 13.17 & \\ & & MS-CASPT2 & 13.51 & 13.26 & 13.21 & 13.21 & \\ & & XMS-CASPT2 & 13.50 & 13.25 & 13.20 & 13.20 & \\ & & PC-NEVPT2 & 14.35 & 13.42 & 13.11 & 13.04 & \\ & & SC-NEVPT2 & 13.57 & 13.33 & 13.26 & 13.26 & \\ \\ Formaldehyde & $1\,^1A_1 \ra 3\,^1A_1$ & FCI & 10.86(1) & 10.45(1) & 10.35(3) & & 9.82$^c$ \\ & $n,n \ra \pis,\pis$ & CCSDTQP & 10.86 & & & & \\ & & CCSDTQ & 10.87 & 10.44 & & & \\ & & CCSDT & 11.10 & 10.78 & 10.79 & 10.80 & \\ & & CC3($\%T_1$)& 11.49(5\%) & 11.22(4\%) & 11.20(5\%) & 11.19(34\%) & \\ & & CASPT2 & 10.80 & 10.38 & 10.27 & 10.26 & \\ & & MS-CASPT2 & 10.86 & 10.45 & 10.35 & 10.34 & \\ & & XMS-CASPT2 & 10.87 & 10.47 & 10.36 & 10.34 & \\ & & PC-NEVPT2 & 10.84 & 10.37 & 10.26 & 10.25 & \\ & & SC-NEVPT2 & 10.87 & 10.40 & 10.30 & 10.29 & \\ \\ Glyoxal & $1\,^1A_g \ra 2\,^1A_g$ & FCI & 5.60(1) & 5.48(0) & & & 5.66$^k$ \\ & $n,n \ra \pis,\pis$ & CCSDT & 6.24 & 6.22 & 6.35 & & \\ & & CC3($\%T_1$)& 6.74(0\%) & 6.70(1\%) & 6.76(1\%) & 6.76(1\%) & \\ & & CASPT2 & 5.58 & 5.47 & 5.42 & 5.43 & \\ & & PC-NEVPT2 & 5.66 & 5.56 & 5.52 & 5.52 & \\ & & SC-NEVPT2 & 5.68 & 5.58 & 5.55 & 5.55 & \\ \\ Hexatriene & $1\,^1A_g \ra 2\,^1A_g$ & CC3($\%T_1$)& 5.78(65\%) & 5.77(67\%) & & & 5.58$^g$ \\ & $\pi,\pi\ra \pis,\pis$ & CCSDT & 5.64 & & & & \\ & & CASPT2 & 5.62 & 5.61 & 5.58 & 5.58 & \\ & & PC-NEVPT2 & 5.67 & 5.66 & 5.64 & 5.64 & \\ & & SC-NEVPT2 & 5.70 & 5.69 & 5.67 & 5.67 & \\ \\ Nitrosomethane & $1\,^1A^\prime \ra 2\,^1A^\prime$ & FCI & 4.86(1) & 4.84(2) & 4.76(4) & & 4.72$^l$ \\ & $n,n \ra \pis,\pis$ & CCSDT & 5.26 & 5.26 & 5.29 & & \\ & & CC3($\%T_1$)& 5.73(2\%) & 5.75(4\%) & 5.76(3\%) & 5.74(2\%) & \\ & & CASPT2 & 4.93 & 4.88 & 4.79 & 4.78 & \\ & & PC-NEVPT2 & 4.92 & 4.88 & 4.79 & 4.78 & \\ & & SC-NEVPT2 & 4.94 & 4.90 & 4.81 & 4.80 & \\ \\ Nitroxyl & $1\,^1A^\prime \ra 2\,^1A^\prime$ & FCI & 4.51(0) & 4.40(1) & 4.33(0) & 4.32(0) & \\ & $n,n \ra \pis,\pis$ & CCSDTQP & 4.51 & & & & \\ & & CCSDTQ & 4.54 & 4.42 & & & \\ & & CCSDT & 4.81 & 4.76 & 4.79 & 4.80 & \\ & & CC3($\%T_1$)& 5.28(0\%) & 5.25(0\%) & 5.26(0\%) & 5.23(0\%) & \\ & & CASPT2 & 4.55 & 4.46 & 4.36 & 4.34 & \\ & & PC-NEVPT2 & 4.56 & 4.46 & 4.37 & 4.35 & \\ & & SC-NEVPT2 & 4.58 & 4.48 & 4.40 & 4.38 & \\ \\ Pyrazine & $1\,^1A_g \ra 2\,^1A_g$ & CC3($\%T_1$)& 9.27(7\%) & 9.17(28\%) & 9.17(12\%) & & \\ & $n,n \ra \pis,\pis$ & CASPT2 & 8.06 & 7.91 & 7.81 & 7.80 & \\ & & PC-NEVPT2 & 8.25 & 8.12 & 8.04 & 8.04 & \\ & & SC-NEVPT2 & 8.27 & 8.15 & 8.07 & 8.07 & \\ \\ & $1\,^1A_g \ra 3\,^1A_g$ & CC3($\%T_1$)& 8.88(73\%) & 8.77(72\%) & 8.69(71\%) & & \\ & $\pi,\pi \ra \pis,\pis$ & CASPT2 & 8.91 & 8.85 & 8.77 & 8.77 & \\ & & PC-NEVPT2 & 9.12 & 9.07 & 9.00 & 9.00 & \\ & & SC-NEVPT2 & 9.16 & 9.12 & 9.05 & 9.05 & \\ \\ Tetrazine & $1\,^1A_g \ra 2\,^1A_g$ & CCSDT & 5.86 & 5.86 & & & 4.66$^m$ \\ & $n,n \ra \pis,\pis$ & CC3($\%T_1$)& 6.22(1\%) & 6.22(1\%) & 6.21(1\%) & 6.19(1\%) & \\ & & CASPT2 & 4.86 & 4.79 & 4.69 & 4.68 & \\ & & PC-NEVPT2 & 4.75 & 4.70 & 4.61 & 4.60 & \\ & & SC-NEVPT2 & 4.82 & 4.78 & 4.69 & 4.68 & \\ \\ & $1\,^1A_g \ra 1\,^1B_{3g}$ & CC3($\%T_1$)& 7.64(0\%) & 7.62(2\%) & 7.62(1\%) & 7.60(1\%) & 5.76$^n$,6.01$^m$ \\ & $n,n \ra \pis_1,\pis_2$ & CASPT2 & 6.00 & 5.95 & 5.85 & 5.85 & \\ & & PC-NEVPT2 & 6.25 & 6.22 & 6.15 & 6.14 & \\ & & SC-NEVPT2 & 6.30 & 6.27 & 6.20 & 6.20 & \\ \\ & $1\,^1A_g \ra 1\,^3B_{3g}$ & CC3($\%T_1$)& 7.35(5\%) & 7.33(5\%) & 7.35(6\%) & 7.34(6\%) & 5.50$^o$ \\ & $n,n \ra \pis_1,\pis_2$ & CASPT2 & 5.54 & 5.47 & 5.39 & 5.39 & \\ & & PC-NEVPT2 & 5.63 & 5.58 & 5.51 & 5.51 & \\ & & SC-NEVPT2 & 5.69 & 5.64 & 5.57 & 5.57 & \\ \end{tabular}