Broadening and Shift of the D₁ and D₂ Lines of Rb Atoms by Neon: Resolving Hyperfine Components in a Half-Wave Cell Using Double Differentiation with Respect to Frequency

Abstract

A cell with a submicron thickness was used to measure the broadening and shift of the D₁ and D₂ lines of Rb atoms by neon. The resolution of hypefine components is achieved by a combination of two techniques. First, the Rb vapor column thickness in the direction of propagation of the laser radiation was chosen equal to half of its wavelength λ under conditions of resonance with the atomic transition frequency. For rubidium atoms λ/2 ~ 400 nm. At a nanocell thickness L ~ λ/2, in the transmission spectrum A(ν), the spectral lines of atomic transitions are narrowed due to the exclusion of Doppler broadening. Second, further narrowing of the detected signals was achieved by the double differentiation of the transmission spectrum, A''(ν). The transmission spectra of pure rubidium vapor and rubidium vapor with the addition of neon have been measured at different pressures. The measured values of the shift coefficients of the D₁ and D₂ lines of rubidium in the presence of Ne were –1.1 ± 0.2 MHz/Torr and –2.1 ± 0.2 MHz/Torr, respectively. The broadening coefficients of the D₁ and D₂ lines coincide and are equal to 10 ± 1 MHz/Torr. Due to its high spectral resolution, this technique allows separate measurements for each individual transition.