Daniel D. Konowalow

The molecular electronic structure of the lowest 1Σ+g, 3Σ+u, 1Σ+u, 3Σ+g, 1Πu, 1Πg, 3Πu, and 3Πg states of Na2

The multiconfiguration self‐consistent field wave functions and potential energy curves for the lowest lying 1Σ+g, 1Σ+u, 3Σ+g, 3Σ+u, 1Πg, 1Πu, 3Πg, and 3Πu states of Na2 are reported. We find good agreement with recent experimental estimates of the dissociation energies for the 1Σ+g and 1Σ+u states. We find the long range hump in the B 1Πu curve to have its maximum height of 520 cm−1 above the separated atom asymptote at R=6.45±0.1 A; recent experimental estimates of the height are 474 and 554±120 cm−1.

The molecular electronic structure of the twenty-six lowest lying states of Li2 at short and intermediate internuclear separations

Abstract We compute and analyze the potential energy for the 26 lowest lying states of Li 2 which correspond asymptotically to the interaction of Li(2s 2 S) with Li(2s 2 S), Li(2p 2 P) or Li(3s 2 S), and the interaction of Li(2p 2 P) with Li(2p 2 P). Results are compared with available experimental and quantum mechanical potential energy curves and molecular constants. The errors in the present calculations are of nearly equal magnitude to, and in the opposite sense of, the optimized valence configuration calculations of Konowalow and Olson. Thus, a composite of the two forms a “most likely” ab initio potential curve which compares favorably with the most recent experimental results.

The electronic structure and spectra of the X 1Σ+g and A 1Σ+u states of Li2

The potential energy curves for the X 1Σ+g and the A 1Σ+u states of Li2 have been calculated on the single configuration Hartree–Fock–Roothaan (HF) level, and on the multiconfiguration self‐consistent‐field (MCSCF) level. The MCSCF results give binding energies De (X 1Σ+g) =8297 cm−1 and De (A 1Σ+u) =9299 cm−1; a semiempirical scaling which reproduces the experimental vibrational energy level spacings suggests ’’most‐likely’’ dissociation energies De′ (X 1Σ+g=8450±100 cm−1 and De′ (A  (1Σ+u) =9400±100 cm−1.

Electronic structure and spectra of the lowest five 1Σ+ and 3Σ+ states, and lowest three 1Π, 3Π, 1Δ, and 3Δ states of NaK

We calculate the potential energy curves for all molecular states of NaK which may be obtained from the interactions Na(3s)+K(4s), Na(3s)+K(4p), Na(3p)+K(4s), Na(3s)+K(5s), Na(3s)+K(3d), and for the Δ states corresponding to the interactions Na(3d)+K(4s) and Na(4p)+K(4p) by full‐valence configuration interaction computations which utilize effective core potentials to describe the core electrons, the core‐valence orthogonality constraints, and the core‐valence correlation (CVC) energy. The differences between our computed curves and those deduced from experimental spectra are generally small and can be accounted for by: (1) the modest size of the basis set, which is insufficiently diffuse to describe Na− and K− resonances associated with excited charge transfer interactions and related molecular Rydberg character, and (2) the approximate way in which the CVC interaction is included.

Accurate potential energy curves for the 3Σ+u and b3Σ+g states of Li2

Abstract Accurate multi-configuration SCF calculations of the potential energy curves for the 3 Σ + u and b 3 Σ + g states of Li 2 are presented. The experimental detection of these states is discussed. The implications of the crossing of the a 3 Π u state potential with the 3 Σ + u potential for a poposed Li 2 laser is discussed.

Long-range interactions of Li(n = 2) states with each other and the long-range interaction of Li(2s2S) with Li(3s2S)

Abstract We compute and analyze the potential energy for the twenty-six lowest-lying states of Li 2 which correspond asymptotically to the interaction of Li(2s 2 S) with Li(2s 2 S). Li(2p 2 P) or Li(3s 2 S), and the interaction Li(2p 2 P) with Li(2p 2 P) to obtain the leading terms of the first-order electrostatic energies, and the second-order dispersion energies. Ion-pair perturbations are found to dominate the potential curves of several states. The polarizabilities of Li 2s, 2p and 3s in various fields are calculated.

The lowest 1Πg, 3Πg, 1Πu and 3Πu states of Li2

Abstract The potential energy curves for the lowest 1 Π g , 3 Π g , 1 Π u and 3 Π u states of Li 2 have been calculated on the single configuration Hartree—Fock—Roothaan, (HF), level and on the multiconfiguration SCF level by using between two and four configurations for each state. We present an improved MC SCF potential curve for the B 1 Π u state and present for the first time MC SCF potential curves for the 1 Π g 3 Π g and 3 Π u states. We show the 1 Π g and 3 Π u states to be bound and the 3 Π g state to be unbound with respect to separated HF atoms. The shapes of the potentials of these states are discussed in terms of avoided crossings of Hartree—Fock curves and in terms of the dispersion interactions at long range which are dominated by the C 3 R −3 term. A detailed comparison with the long-range behavior of the corresponding states of H 2 helps to understand the substantially different appearance of the potential curves for these isovalent molecules. For the Li 2 Π states we present an improved value of C 3 = ±5.6594 ± 0.0010 au (the 1 Π u and 3 Π g states have the positive sign).

Electronic assignments of the violet bands of sodium

Abstract The puzzling violet bands of sodium ( ≈ 425-460 nm), known since 1932, are shown conclusively to arise from the superposition of two distinct continuum emission bands - one singlet (2 1 Σ + u → X 1 Σ + g ) and one triplet (primarily 2 3 Π g → 1 3 Π u + ). Each continuum emission system shows complex interference structure arising from multiple branches of the Mulliken difference potential.

Electronic transition dipole moment functions and difference potentials for transitions among low-lying states of Li2 and Na2

Abstract Electronic transition dipole moment functions based on ab initio multiconfiguration self-consistent field wavefunctions are computed for the transitions 1Σu+-1Σg+, 3Σg+-3Σu+, 1Πu-1Σg+, 3Πg-3Σu+, 1Σu+-1Πg, 3Σg+-3Πu, 1Πu-1Πg, and 3Πg-3Πu in Li2 and Na2. (In each case the states are the lowest lying of their symmetry.) We also calculate the matrix element 〈3Σu+|i(Lx - iLy)|3Πu〉 for the predissociation of the 3Πu state by the 3Σu+ state. Several unobserved spectral features are predicted.

Li2 and Na23Σg+–3Σu+ excimer emission

Ab initio calculations show the 3Σg+–3Σu+ in Li2 and Na2 dimers to be primarily a near‐infrared continuum with respective v′=0 lifetimes of 62 and 15 nsec. The peak stimulated emission cross section for v′=0 is 4.5×10−−6 at 1.3μ for Li2 and 1.8×10−15 cm2 at 0.83μ for Na2. These calculations suggest a tunable high gain, near‐infrared laser excimer if the 3Σg+ state can be populated sufficiently rapidly.