Diffuse series
![Graph showing wavelengths of the diffuse series of sodium plotted against N-2 (inverse square) making assumptions of different starting point of n. Blue diamond starts with n=2, red square starts with n=3, green triangle starts with n=4, violet X starts with n=5. Only with starting n of 3 is a straight line achieved[11]](/Images/godic/202501/09/Sodium_diffuse_series_with_different_origins5802.png")
The diffuse series is a series of spectral lines in the atomic emission spectrum caused when electrons jump between the lowest p orbital and d orbitals of an atom. The total orbital angular momentum changes between 1 and 2. The spectral lines include some in the visible light, and may extend into ultraviolet or near infrared. The lines get closer and closer together as the frequency increases never exceeding the series limit. The diffuse series was important in the development of the understanding of electron shells and subshells in atoms. The diffuse series has given the letter d to the d atomic orbital or subshell.