High pressure line shapes of the Rb D1 and D2 lines for 4He and 3He collisions. (November 2016)

• Record Type: Journal Article
• Authors: Miller, Wooddy S.; Rice, Christopher A.; Hager, Gordon D.; Rotondaro, Mathew D.; Berriche, Hamid; Perram, Glen P.
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 184(2016)
• Page Start: 118
• Page End: 134
• Publication Date: 2016-11
• Subjects: Line shape -- Rubidium -- Asymmetric broadening -- Potentials; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2016.06.027
• Languages: English
• ISSNs: 0022-4073

Abstract

Abstract: Line shapes for the Rb D 1 ( 5 S 1 / 2 2 ↔ 5 P 1 / 2 2 ) and D 2 ( 5 S 1 / 2 2 ↔ 5 P 3 / 2 2 ) transitions with 4 He and 3 He collisions at pressures of 500–15, 000 Torr and temperatures of 333–533 K have been experimentally observed and compared to predictions from the Anderson–Talman theory. The ground X Σ 1 / 2 + 2 and excited A Π 1 / 2 2, A Π 3 / 2 2, and B Σ 1 / 2 + 2 potential energy surfaces required for the line shape predictions have been calculated using a one-electron pseudo-potential technique. The observed collision induced shift rates for 4 He are dramatically higher for the D 1 line, 4.60±0.12 MHz/Torr, than the D 2 line, 0.20±0.14 MHz/Torr. The asymmetry is somewhat larger for the D 1 line and has the same sign as the shifting rate. The 3 He broadening rate for the D 2 line is 4% larger than the 4 He rate, and 14% higher for the D 1 line, reflecting the higher relative speed. The calculated broadening rates are systematically larger than the observed rates by 1.1–3.2 MHz/Torr and agree within 14%. The primary focus of the current work is to characterize the high pressure line shapes, focusing on the non-Lorentzian features far from line center. In the far wing, the cross-section decreases by more than 4 orders of magnitude, with a broad, secondary maximum in the D 2 line near 735 nm. The potentials do not require empirical modification to provide excellent quantitative agreement with the observations. The dipole moment variation and absorption Boltzmann factor is critical to obtaining strong agreement in the wings.