Knowledge Bank

Level crossing spectroscopy in the vaccum ultraviolet has been performed on the excited 2p states of atomic hydrogen. This experiment has yielded a high precision measurement of the fine structure splitting for the 2p states. A value of the Sommerfeld fine structure constant $\alpha$ has been obtained from this measurement. The importance of this fundamental constant will be discussed as will the theory of level crossing spectroscopy and the details of vacuum ultraviolet level crossing techniques.