Knowledge Bank

Ionization potentials were determined by examining the long wavelength limit of photoionization yield curves obtained by a method described previously. Values for $CS2,H2S,C6H6$, toluene, p-xylene, $C2H4$, butadiene, and $CH3I$ agreed with spectroscopic values obtained by Price and coworkers. Ionization potentials of $NH3$, NO, acetone, methyl-ethyl-ketone, $CH3OH$, and $C2H5OH$ will also be reported. Improved energy measurements showed that the photoionization cross sections of NO in the region 1070A-1340A obtained earlier were about 40 percent too low. The photoionization cross section of $NH3$ was found to rise gradually with decreasing wavelength in the region $1200A-1060A$ and to reach a value of $9\times 10-18$ $cm2$ at 1060A.