Spectroscopic study of the Σ-potential of the system Li3D+He at large separations

Staemmler

2001

A quantum simulation of the thermally averaged translational-rovibronic spectrum of Li*He associated with the 3D(Σ,Π,Δ)←2P(Σ,Π) and 3P(Σ,Π)←2P(Σ,Π) transitions is performed, using as input data accurate potentials and dipole transition moment functions derived from ab initio calculations. A few inaccuracies of the potentials existing in the previous simulation of this spectrum are corrected, and previously neglected bound states are taken into consideration. The spectral profiles arising from different molecular channels are calculated with a high degree of accuracy, and the total absorption cross section summed over all the contributions is compared with the experimental spectrum. It is demonstrated that the inclusion of bound states considerably improves the agreement with the experimental values which finally seems to be almost very good. This result testifies to the accuracy of input data used for simulation.

Section: Some Remarks On the Experimental Spectrum And Its Interpreta...mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Quantum calculation of the excitation spectra of Li*He probing interaction potentials and dipole moments

Grycuk

Staemmler

2001

“…So far experimental potential determinations have mainly been concerned with the lowest electronic states X 2 + , A 2 and B 2 + of AX [1][2][3][4][5]. Recently, for LiHe and LiNe higher Rydberg states have also been studied [6][7][8][9], the electronic structure of which is particularly simple. In LiHe, the potential curve in the 3D state was determined from the rotationally resolved 2P → 3D band spectrum [6].…”

Section: Introductionmentioning

confidence: 99%

Optical transitions in excited alkali + rare-gas collision molecules and related interatomic potentials:

Makonnen

Kaiser

et al. 1996

A comparison is made of experimental far-wing profiles for the system Li(2P → 3D)He with quantum calculations of thermally averaged free-free continua. Using input adiabatic potentials and transition moment functions from both ab initio and semi-empirical approaches, the comparison shows: (i) new ab initio potentials for Li * (2P, 3P, 3D)He reproduce the spectral positions of the observed rainbow satellites well; the height of the 3D barrier predicted agrees with experiment to within ±15 cm −1 , whereas its position is too large by 0.3 a 0 ; (ii) potentials obtained with various semi-empirical methods reproduce the satellite structure qualitatively, but are generally too repulsive in the 3D state at intermediate and large internuclear separations; (iii) transition moment functions for the asymptotically forbidden 2P → 3P transitions reproduce, with different degrees of accuracy, the intensity of the red-wing satellite related to the 3P potential extremum around 12 a 0 . The vibrational energies in the 2P and 3D states calculated with the ab initio potentials reproduce to within a few cm −1 those obtained from rotationally resolved band spectra reported in the literature.

“…Spectroscopic studies of alkali-rare-gas molecules [1][2][3][4][5][6][7] have recently provided accurate potentials or potential parameters for a number of excited states of these molecules in the range of thermal energies.…”

Section: Introductionmentioning

confidence: 99%

Optical transitions in excited alkali + rare gas collision molecules and related interatomic potentials:

Kaiser

Rebentrost

et al. 1998

Theoretical and experimental collision induced spectra associated with the transitions 2P → 3D * , 3P * as well as 3S → 2S in Li * Ne are compared. By means of quantum mechanical simulations, using new ab initio (AI) and semiempirical (MP) potentials and transition moment functions, the contributions from free-free and bound-free transitions on the individual molecular channels to the spectra are analysed and the accuracy of the potentials is tested. In particular, from the excitation spectra 2P → 3D measured with absolute intensity scaling, the experimental 3D potential in the barrier region 8-15 a 0 is obtained by inversion. It is found that the barrier parameters of the AI method reproduce the experimental values within error limits, whereas the barrier height from the MP approach is off by about 100 cm −1 . Beyond the barrier maximum the theoretical energies decrease faster than the experimental ones. The experimental 3S → 2S spectrum is well reproduced by the calculations with the AI data set, showing that the latter are accurate within their limits of confidence.