RubidiumD₁andD₂atomic lines’ pressure broadened by ground-state helium atoms

Abstract

Full quantum calculations are performed to determine the spectral broadening of the rubidium D1 and D2 lines induced by collisions with helium perturbers. The potential curves of the low-lying RbHe molecular states, as well as the corresponding transition dipole moments, are generated theoretically with ab initio methods based on SA-CASSCF-MRCI calculations, including the spin–orbit effects. The absorption and emission coefficients at wavelengths lying between 650 and and temperatures ranging from 100 to 3000 K are determined. The absorption profile reveals it is dominated by the free–free transitions, whereas the emission spectral shape arises from the free–free and bound–free transitions. The resulting red- and blue-wing profiles are compared with previous experimental and theoretical works.

Spectroscopy of high pressure rubidium-noble gas mixtures

“…The shift can be extracted from the spectra to be (4.82 ± 0.07) GHz/bar for the D1and (2.01 ± 0.12) GHz/bar for the D2-line, respectively. For the D1-transition this is around 40% larger than the literature values, however those were measured at lower pressures of [35] and [36].…”

“…For blue-detuning the emission decreases much faster, yet around 735 nm an additional feature in the form of a satellite resonance is visible. In the literature predicted spectra for this system at slightly different parameters (temperature of 1000 K and a density of 1 × 10 20 cm −3 , equating to around 14 bar at that temperature) can be found [35,36]. When comparing the general form of the emission spectra they are nevertheless in good agreement.…”

“…The use of such high pressures well ensures a full redistribution of fluorescence, as is necessary to apply the above described method (see chapter 3) of extracting the absorption strength from the detected fluorescence yield, as this method relies heavily on the spectral profile of the emission being independent of the excitation frequency. The absorption shows a smooth decline in the absorption strength reddetuned to the resonances while in the blue wing a satellite resonance at 865 nm is visible, which becomes visible at the same position in the calculated spectra in [35] for temperatures of 320 K and larger. This satellite is of certain interest for the realization of exciplex-pumped alkali-gas lasers [37].…”

“…A pressure-dependent broadening and blue-shift is visible. Inset: The emission spectrum at 4.1 bar shown in logarithmic scale for better comparison with the data in[35]…”

Phase-modulated electronic wave packet interferometry reveals high resolution spectra of free Rb atoms and Rb*He molecules

“…Despite the availability of more recent ab initio PECs of the Rb*He exciplex [60][61][62] , we compare our data with the semi-empirical potentials calculated by Pascale 52 , which is currently the only model comprising highly excited electronic states. Pascale's pair potentials have proven to accurately describe the energetic structure of alkali-helium exciplexes in many cases 38,44,46,51 .…”