Abstract: Using the method of density functional B3LYP, we optimized the ground state stable configuration of gas phase lysine (Lys) molecules and Lys^2- at the level of the 6-311+G(2df) basis set. The method of time dependent density functiona
l theory (TD-DFT) was used to investigate the characteristics of single excited state of gas phase Lys molecule and chargedion system. The results show that the energy of the system increases when the Lys molecular system captures dual electrons, the energy difference between the S1 and S0 decreases, the fluorescence wavelength of the molecular system increases, and the number of electron transition orbits of the S7 single excited state decreases.

Key words: lysine, ion, single excited state, orbital transition