Electron-impact excitation of the sodium atom

Absolute electron-impact optical-excitation functions of 26 transitions of the sharp, principal, diffuse, fundamental, and $\mathrm{nP}-4S$ series of sodium have been measured in the impact-energy range 0-150 eV. The determination of the target-atom number density was made by measuring the attenuation of sodium resonance radiation from a fluorescence cell upon passage through the collision chamber. Direct-excitation cross sections of 14 states ($4S$, $5S$, $6S$, $7S$, $3P$, $4P$, $5P$, $6P$, $3D$, $4D$, $5D$, $6D$, $6F$, and $7F$) have been determined from the measured optical-excitation cross sections with the aid of radiative-transition probabilities taken from the literature. These direct-cross-section results are compared with theoretical calculations based upon the Born approximation and the multistate-close-coupling approximation. Measurements were also made of the polarization of several sharp, principal, and diffuse series-resolved doublets, and from these results the direct-excitation functions of the separate orbital magnetic sublevels of the $3P$ state have been determined.