Knowledge Bank

“The absorption of ultraviolet radiation by sodium vapor, and the associated ionization, has been investigated from 1040{\AA} to 3500{\AA} using a two-metre McPherson normal incidence spectrometer and an absorption chamfer of the type described by Ditchburn and $Hudson.1$ The atomic cross section at the series limit (2412 {\AA}) was found to be $11.2\pm 1.0\times 10-20cm2$, in good agreement with the previous result obtained by Ditchburn, Jutsum and $Marr.2$ The atomic cross section decreases to a minimum at 1900{\AA} and then increases again towards shorter wavelengths. Continuous molecular absorption was observed from 3500{\AA} to 1700{\AA} and ion chamber measurement indicate that this absorption is due to an ionization continuum. Ion current peaks were also seen between 2413{\AA} and 3500{\AA} at wavelengths corresponding to the series absorption lines of the sodium atom. Curves will be presented showing the variation with wavelength of both the atomic cross section and the relative molecular cross section.”