Study of the Valence and Rydberg States of a Lithium Dimer by the Multi-reference Configuration-interaction Method

Abstract

Convergent all-electron multi-reference configuration-interaction (MRCI) calculations are performed for a lithium dimer with Kaufmann's Rydberg basis functions. A comparison of the results of these calculations with those of the effective core potential/core polarization potential (ECP/CPP) method and experimental data reveals the deficiency of the all-electron ab initio method. The deficiency is related to the mere 51.9% attainment of electron correlation for the ground state. The percent attainment of electron correlation for the first excited state is slightly better than that for the ground state, preventing us from obtaining better agreements with experimental data by means of increasing the size of basis sets. The Kaufmann basis functions are then used with the ECP/CPP method to obtain the accurate convergent potential energy curves for the

Unexpected properties of non‐autoionizing doubly excited states of the H2 molecule

“…This peculiarity is not reported in the study of the singly excited states, [10] but can occur in highly excited Rydberg states. For example, the 3 R u 1 symmetry of the Lithium dimer [24,25] presents one repulsive state interlaced between bound states. [25] However, we stress that accurate results for highly excited states are scarce in literature.…”

“…For example, the 3 R u 1 symmetry of the Lithium dimer [24,25] presents one repulsive state interlaced between bound states. [25] However, we stress that accurate results for highly excited states are scarce in literature. From the above description, it emerges that some states undergo shallow minima at unusual large internuclear distances.…”

Analytic potentials and vibrational energies for Li$_{2}$ states dissociating to $\mbox{Li}\left(2S\right)+\mbox{Li}\left(3P\right)$. Part 1: The $^{2S+1}Π_{u/g}$ states

“…where Z is the effective nuclear charge, a µ = a 0 mN µ is the Bohr radius scaled by the ratio of the mass of the nucleus m N to the reduced mass µ of the atom. And for alkali atoms, the principal quantum number n is replaced by n − α(l), where α(l) is the quantum defect and can be found in standard references such as Ref [29] of [45]. Using α(p) = 1.59 for Li, assuming that Table I.…”

“…Due to the shortage of measurements on the Li 2 2S+1 Πu /g states dissociating to 2S + 3P , the most accurate potentials come from purely ab initio calculations. For the 3c(3 3 Σ + g ) and 3A(3 1 Σ + u ) states, ab initio calculations were reported in 1985 [25], 1995 [26], 2006 [27] and 2014 [28,29]; and for the 3d(3 3 Π g ) state in 1995 [6] and 2014 [28,29]. But for the rest of the states dissociating to 2S + 3P ; namely 3b(3 3 Π u ), 6X(6 1 Σ + g ), 3B(3 1 Π u ), 3C(3 1 Π g ), and 6a(6 3 Σ + u ); the only ab initio calculations reported were in [26,28,29].…”

“…For the 3c(3 3 Σ + g ) and 3A(3 1 Σ + u ) states, ab initio calculations were reported in 1985 [25], 1995 [26], 2006 [27] and 2014 [28,29]; and for the 3d(3 3 Π g ) state in 1995 [6] and 2014 [28,29]. But for the rest of the states dissociating to 2S + 3P ; namely 3b(3 3 Π u ), 6X(6 1 Σ + g ), 3B(3 1 Π u ), 3C(3 1 Π g ), and 6a(6 3 Σ + u ); the only ab initio calculations reported were in [26,28,29]. All of these ab initio papers also reported potentials for states dissociating to lower asymptotes, where plenty of experimental data is available to gauge the quality of the calculations.…”