Absolute photoabsorption cross section of theKshell of atomic lithium

The absolute cross section of atomic lithium has been measured in the spectral range from 175 to 110 Å thus extending previous work to shorter wavelengths. Good agreement is found with theoretical predictions. The autoionizing-resonant-structure excitation between 176 and 160 Å has been measured and line-profile parameters obtained for several of the resonances. The resonant structure for core excitation associated with $N=3\mathrm{}$ and $N=4\mathrm{}$ principal quantum numbers is found to bear a close relationship to the analogous excitations in helium. A new classification of the resonant structure is given and comparisons made with theoretical results. A discussion of the total oscillator strength for $K$-shell excitation in lithium is given and the results obtained from the present and previous work are compared with the Thomas-Reiche-Kuhn sum-rule value.