Pressure broadening and frequency shift of the 5S_1/2→ 5D_5/2and 5S_1/2→ 7S_1/2two photon transitions in⁸⁵Rb by the noble gases and N₂

Abstract

Doppler free two photon absorption spectroscopy was employed to measure the pressure broadening and frequency shift rates of the 5S1/2 (F = 3) → 5D5/2 (F = 5, 4, 3, 2, 1) (778.105 nm) and the 5S1/2 (F = 2) → 7S1/2 (F = 2) (760.126 nm) two photon transitions in 85Rb by the noble gases and N2. To our knowledge, these rates are reported on for the first time. The self-broadening and shift rate of the 5S1/2 (F = 3) → 5D5/2 (F = 5, 4, 3, 2, 1) transition and self -broadening rate of the 5S1/2 (F = 2) → 7S1/2 (F = 2) transition were also measured. The temperature dependence of the self-frequency shift (Rb-Rb collisions) of these transitions is presented. Helium diffusion rates through Quartz and Pyrex cells are also calculated and the implication of helium diffusion through glass vapor cells is discussed in regards to atomic frequency standards based on these transitions. Experimental pressure broadening and shift rates are compared to theoretically calculated rates assuming a 6, 8 or 6, 8, 10 difference potential and pseudo potential model. Reasonable agreement is achieved between experimental and theoretical values.

Aging studies on micro-fabricated alkali buffer-gas cells for miniature atomic clocks

“…Permeation of He through silica and borosilicate glasses was reported by Norton 19 and Harding 20 for the temperature range of À80 C to 700 C and by Altemose 21 for 100 C to 600 C. Ne permeation was studied by Wortmann and Shackelford 22 for vitreous silica glasses at 0 C to 50 C, by Kanezashi et al 23 for silica glass at 300 C to 600 C, and by Shelby 24 for borosilicate glasses at 200 C to 560 C. Recently, Zameroski et al 25 have discussed the impact of He permeation into an alkali vapor cell on their measurement of collisional shift rates of Cs optical transitions, using data from Altemose. 21 To summarize, most of these works reported on the permeation of He through different glasses at elevated temperature ranges where permeation is enhanced, 19 while no study has been reported so far on the impact of Ne permeation through borosilicate glass in atomic clock applications.…”

Compact Optical Atomic Clock Based on a Two-Photon Transition in Rubidium

“…The collisional shift of Rydberg states of alkali metals has been a subject of research since E. Fermi formulated a pseudo-potential to describe the interaction of the atoms loosely bound electron with the perturber [37]. There has been a large disagreement in the literature about the measurement of the collisional shift [26,34,38]. We measured a collisional shift for our 87 Rb enriched vapor cell by varying the vapor cell temperature and measuring the clock shift of our locked laser system.…”

“…Included is a fit using a sum of four Lorentzian peaks of equal width and with relative peak heights and detunings constrained by the values presented in [24]. The fitting procedure results in a full-width at half-maximum linewidth of 609 kHz, which exceeds the natural linewidth by a factor of 1.8, which we expect is due to line broadening from helium collisions [34]. and short term stability limitations.…”

Two-Photon Spectroscopy in Rb for an Optical Frequency Standard

“…The use of Doppler free two-photon absorption spectroscopy on these elements is of particular importance, as this method may be used for the measurement of fundamental constants and other metrological applications. In particular, the 778 nm 5S 1/2 →5D 5/2 two-photon transition in 85 Rb is of interest, especially in regards to the establishment of atomic frequency standards [1][2][3][4]. This transition may be accessed through diode lasers or via second harmonic generation of telecom fiber lasers at 1556 nm, thus allowing for a relatively simple set-up incorporating glass vapor cells.…”