Why does each chemical element have its own unique spectral-line

signature? How do emission- and absorption-line spectra work? This

lecture is the second part of a two-part exploration of the interaction

between matter and light, today discussing how the unique spectral-line

signatures of atoms are a reflection of their internal electron

energy-level structure. We will discuss energy level diagrams for

atoms, excitation, de-excitation, and ionization, and do a short

demonstration with gas-discharge tubes and slide-mounted diffraction

gratings. For podcast listeners, the last portion of the class is the

demo, which we do not, unfortunately, have the resources to videotape.

Recorded 2006 Oct 26 in 100 Stillman Hall on the Columbus campus of The

Ohio State University.