3.3.1 C 3 C 3 has been studied previously by Jaffe et. al. They identified a strong transition from the ground state to the first 1 Σ + u electronic state that can be effective in absorption of the radiation flux for the wavelength range 160-190 nm. Following their work, the electronic energy states of C 3 have been computed via the MRCI method using the MolPro software package. The results are compared to the calculations of the TD method. For these calculations, the aug-cc-pVTZ basis set is used and the MRCI energies are computed for D ∞h symmetry. The ground state of the molecule has the D ∞h symmetry and an optimum bond length of 1.2876 Angstrom. Figure represents the bending potential for C 3 molecule obtained using TD method with augmented correlationconsistent valence triple-ζ (aug-cc-pVTZ) basis set. The diamond markers in the figure show the MRCI results from Ref. 18. This comparison shows that the results are in agreement for some of the states. However, a few states are missing when using the TD method to obtain the excited electronic state. Due to the deficiency of the TD method further calculations are done using the MRCI method. It can be pointed out that the 1 Σ + u state, state number 8 in the figure has a minimum near φ = 120 • . Although, the TD method is able to predict the low lying states within chemical accuracy, it is missing states and the errors in the high lying states increases upto 1.5 eV. . . The optimized bond length values for the ground state have been calculated earlier in using the coupled cluster method and are in good agreement with our calculations. These values also match the experimental values given in the review by Orden and Saykally. The optimum geometry for the excited state of interest(SoI) is given in Table along with the rotational constant and normal mode vibration frequencies. The excited state has a linear geometry with bond lengths slightly higher than the ground state. This is expected due to the larger spread of the electron cloud around the atoms. The molecule in the excited state belongs to the D ∞h point group.