Diode laser absorption spectroscopy for teaching undergraduate physics

We describe the application of a 780 nm diode laser in studying the rubidium D2 transitions (5/sup 2/P/sub 3/2/-5/sup 2/S/sub 1/2/) at 780.2 nm., which has a well known energy structure, by frequency scanning the resonance lines and observing the absorption spectrum to illustrate the role of the nucleus in atomic structure beyond the first order leading to hyperfine interaction in /sup 87/Rb. The experiment yields very high resolution and illustrates that with diode lasers it is possible to teach undergraduate physics without recourse to expensive laboratory facilities.