Doublet Separation, Physics 3901, Fall 04

The Fabry-Perot interferometer was used to measure the doublet separation of the sodium doublet and the separation of the hydrogen and deuterium 3 to 2 transitions. The technique involves increasing the mirror spacing to advance one of the doublet members one order with respect to the other.

The measurement of the sodium doublet was assisted by t he fact that at one point in its range it produces an interference pattern with a distinct double-line characteristic. Throughout most of its range it exhibits the more regular interference pattern shown below. This makes it easier to advance the interference one order.

For three runs of the sodium advance, distances of 0.30, 0.28 and 0.31 mm were measured. These distances correspond to doublet separations of 0.58, 0.62 and 0.56 nm respectively compared to an accepted value of 0.6 nm.

The hydrogen-deuterium separation is much harder to measure. A distance of 0.93 mm was measured corresponding to a separation of 0.23 nm.

Experimenters: Morgan Callender, Dominique Sol, Ryan Hennings and Matthew Davis.