Emission spectrum of core-excited Li doublets

Abstract

Configuration-interaction calculations have been carried out for the core-excited ${}_{}{}^2{}_{}{}^{}D_{}^o{}_{}{}^{}$ bound states of neutral Li. The levels $1s2p {}_{}{}^3{}_{}{}^{}P 3d$, $1s2p {}_{}{}^3{}_{}{}^{}P 4d$ and $1s2p {}_{}{}^1{}_{}{}^{}P 3d$ are estimated to lie 524 235.5(3.0), 530 306.1(3.0), and 532 058.8(4.5) ${\mathrm{cm}}^{-1\mathrm{}}$ above the ground state, respectively. Using additional theoretical and experimental data for core-excited Li levels and calculated oscillator strengths, we have developed a consistent scheme for the decay of ${\mathrm{Li}}^{**}$ doublets which explains the main features of this spectrum. Two previously observed lines $\lambda =2846\mathrm{} \mathrm{and} 3661$ Å correspond to transitions between ${}_{}{}^2{}_{}{}^{}D_{}^o{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}P$ bound states, in agreement with an earlier assignment. Three other lines $\lambda =2640, 3144, \mathrm{and} 4590$ Å result from bound states ${}_{}{}^2{}_{}{}^{}D_{}^o{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}P$ decaying into ${}_{}{}^2{}_{}{}^{}D$ and ${}_{}{}^2{}_{}{}^{}P_{}^o{}_{}{}^{}$ core-excited states which undergo rapid autoionization, in agreement with the prominent linewidths exhibited experimentally. Possible spin-forbidden electric-dipole transitions are discussed.