Calculation of autoionization widths for two-electron systems

A procedure is used which combines the truncated diagnoalization method with the open-channel close-coupling approximation in the calculation of widths of autoionization states in two-electron systems. The method is capable of systematically and efficiently calculating the widths for all two-electron systems. Calculations are made for ${}_{}{}^1{}_{}{}^{}P_{}^0{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}P_{}^0{}_{}{}^{}$ helium, and ${}_{}{}^1{}_{}{}^{}P_{}^0{}_{}{}^{}$ hydrogen below the $N=2\mathrm{}$ threshold. In particular, it is found that the lowest member of the third series [classified as $(2,3\mathrm{}c)$)] has a width of 4.61 × ${10}^{-7\mathrm{}}$ eV, four times smaller than any previous calculation. It is also shown that the (+)-(-) classification used by many authors is inadequate to describe these states. Detailed comparison is made with the three- and six-state close-coupling and other calculations.