Europhysics Letters (EPL)
Measurement of the atomic Na(3 P ) lifetime and of retardation in the interaction between two atoms bound in a molecule
K. M. Jones, Paul S. Julienne, Paul D. Lett, William D. Phillips, Eite Tiesinga, Carl J. Williams
Abstract
From molecular spectroscopy of the Na 2 purely long-range 0 − g state we determine the Na(3 P ) lifetime and measure the predicted but previously unobserved effect of retardation in the interaction between two atoms. Our lifetime τ( P 3/2 ) = 16.230(16) ns helps to remove a longstanding discrepancy between experiment and theory. Electron cloud overlap is unimportant in the 0 − g state ( R > 55 a 0 ) and the spectrum is calculated, ab initio , from atomic properties. By measuring the binding energies the 120 MHz correction due to retardation of the resonant-dipole R −3 interaction is confirmed.