Energy Levels and Visible Spectrum of Ne I
The image is in the file, NEONLINES.JPG.
On the image the horizontal lines are energy levels of an excited electron
in Ne I (neutral neon atom). The energies of these levels vary from
16.6 eV, the first excited state at the bottom of the image, to
21.5 eV, the dashed line at the top of the image (the
energy required to ionize the neon atom).
The ground state of the atom is at 0 eV, far below the
bottom of the image. There are many more states not shown near
the ionization energy.
Vertical lines show the allowed electron transitions that emit visible
light. The color of the light emitted is indicated by the color of
the line. The wavelengths range from 400 nm on the left (violet) to
750 nm on the right (red). The brightest lines in the spectrum are
those in the bottom half of the image: yellow, orange, and red. This
is why the light from neon looks orange.
The energy levels were obtained from C. E. Moore,
Atomic Energy Levels, Vol. 1 (U.S. Gov. Printing Office, Washington,
D.C., 1971).