Spin-exchange cross section for electron excitation of Na3S−3Pdetermined by a novel spectroscopic technique

An experimental technique is described which enables determination of the partial cross sections for electron excitation of atoms as a function of changes in spin and orbital angular momentum. This method provides a good signal-to-noise ratio in the energy region near threshold, and could be used to study long- or short-lived excited states of many atomic systems. Measurements for Na $3S-3P$, near-threshold excitation are reported here. The results are generally in good agreement with the close-coupling calculations of D. L. Moores and D. W. Norcross [J. Phys. B 5, 1482 (1972)] for the largest $\Delta m_S$ and $\Delta m_L$ components of the cross section, but not for the component with $\left|\Delta m_S\right|=1\mathrm{}$ and $\left|\Delta m_L\right|=1\mathrm{}$, indicating that the exchange interaction is larger than previously recognized.