Potential energy curves for the Rydberg states of LiHe and the spectrum of Li atoms interacting with He gas

Abstract

Potential curves for the Rydberg states of the LiHe diatomic have been calculated in the ab initio SCF and CEPA approximations (including electron correlation effects) up to the 5s state. The authors present results for potential wells and barriers, quantum defect functions, dissociation energies, vibration levels and oscillator strength functions. The last are used to predict the broadening of some emission and absorption lines of Li atoms under He gas pressure and well as a number of satellite structures in the Li absorption spectrum between 670 and 260 nm.

Theoretical study of pressure broadening of lithium resonance lines by helium atoms

“…10. They are similar in shape to the semi-classical calculations of Jungen and Staemmler [8] and of Erdman et al [9]. There is a satellite near 536 nm which also appears in the emission spectrum but otherwise the absorption coefficients decrease steadily with separation from the position of the resonance line.…”

“…From Table I, we obtain 288.4 cm −1 . An earlier calculation by Jungen and Staemmler [8] yielded 260 cm −1 .…”

“…Recent studies of the potassium and sodium lines have employed classical and semi-classical scattering theories [5,6,7]. Jungen and Staemmler [8] have obtained detailed emission and absorption profiles (in arbitrary units) for the resonance line of lithium for a wide range of temperatures and Erdman et al [9] have presented measurement of the absorption profile of lithium in a gas of helium at a temperature of 2033 K together with the results of a quasistatic semiclassical theory.…”

Study of potential barriers in Σ states of Li* (3P, 3D)-rare gas collision molecules by means of laser excitation spectroscopy

“…Under this point of view, alkali-rare gas systems are very good test cases for two reasons: 1) these systems yield good efficiencies in spectroscopic experiments because of rather intense dipole allowed transitions between lower excited alkali states; 2) they are also very suitable for theoretical studies of interactions due to the possibility of approximately separating core and valence electron in the alkali atom that reduces the interaction with the rare gas atom to a three body problem. Since the atomic interactions are the main physical quantities needed for a good understanding of the collision processes, much effort has been devoted to calculating [1,2], or experimentally determining [3 6] adiabatic potentials.…”

“…For these states, the experiments yield deeper wells at smaller separations than in ab-initio potentials [2J. Also, in Lille the continuous spectrum of free-free transitions 2PX,/7 ~ 3DS has been measured [1][2][3][4][5][6] and from this the asymptotic potential curve for the 3DX-state evaluated. This curve turned out to be significantly less repulsive than obtained from the semiempirical model calculations .…”