Measurement of relative subshell-photoionization cross sections in sodium chloride and sodium fluoride by x-ray-photoelectron spectroscopy

Relative subshell-photoionization cross sections have been measured directly for solid samples of sodium fluoride and sodium chloride by the technique of x-ray-photoelectron spectroscopy. Values are reported for the subshell-photoionization cross sections of the sodium $2s$ and $2p$; chlorine $2s$, $2p$, $3s$, and $3p$, and fluorine $1s$, $2s$, and $2p$ levels relative to the $1s$ level of sodium. To obtain these values from measured photoelectron line intensities, corrections have been made for (i) the transmission efficiency of the electron energy analyzer, (ii) the angular dependence of the differential subshell-photoionization cross section, and (iii) for the attenuation of the hot electrons as they emerge from a solid sample covered by an adsorbed gas layer, by the use of Auger-electron data acquired simultaneously. Very good agreement is found between the results of the present direct measurements and previous approximate subshell-photoionization cross sections deduced from total-photoionization measurements.