To better understand the effect of electric fields on the excitation energies of Chl-a and Chl-c molecules, we have studied these chromophores in the gas phase under the influence of electric fields in different directions. To this end, we have first aligned the gas phaseoptimized pigments in the x -y plane by moving the nitrogen atoms to position very close to the z = 0 plane. Moreover, we have rotated the molecule in the x -y plane such that maximum effect of electric field in the y direction is observed. Subsequently, seven calculations were performed for each chromophore, i.e., no electric field as well as fields in the ±x, ±y, and ±z directions. The field strength in all cases was set to 0.01 in atomic units, i.e., e/a 2 0 , corresponding to 5.14 V/Å. TD-DFT calculations with the CAM-B3LYP functional and the Def2-TZVP basis set were performed for all excited state calculations as implemented in the ORCA program . The results are listed in Table and the associated density differences are depicted in Fig. for fields in the positive x, y, and z directions.