Accurate and coupled Hartree-Fock calculations of the third-harmonic coefficient (THC) of ${\mathrm{Li}}^{+}$ are presented. The zero-frequency THC in the Hartree-Fock case is 0.2190 a.u. and the accurate THC is 0.2411 a.u. The $1s^2\to 1s2p$ transition wavelength is determined to be 196.7 Å from the Hartree- Fock calculation and 199.0 Å from the accurate calculation, whereas the observed value is 199.3 Å.

• Received 23 October 1973

DOI:https://doi.org/10.1103/PhysRevA.9.1456