Pressure broadening and frequency shift of theD1andD2lines of Rb and K in the presence of3He and

Abstract

We report the results of a study of the pressure broadening and resonant frequency shift of the absorption profiles of the D1 and D2 lines of Rb and K in the presence of 3 He and N2 gases over a range of number densities. We have also examined the temperature dependence of the broadening and shift over a range of approximately 340 to 400 K. We compare our results for the broadening and shift coefficients for Rb D1 and D2 to current values and present coefficients for K D1 and D2, which to our knowledge have not previously been measured at these densities and temperatures.

Accurate Determination of an alkali-inert gas diffusion coefficient using coherent transient emission from a density grating

“…We have demonstrated a distinctive and accurate measurement of the diffusion coefficient of Rb in N 2 relevant to magnetometry. Ideally, the systematic effect due to the N 2 concentration should be measured at buffer gas concentrations of several atmospheres so that spectra can be fit to a smooth lineshape as in reference [45,51]. Since the buffer gas pressure in our isotopically purified rubidium cell could not be changed, we fit the pressurebroadened spectrum to a function appropriate for our pressure range where the hyperfine splitting is significant.…”

“…7. Recent examples of pressure broadening studies in alkali vapors relevant to magnetometry are described in references [45,46,51]. In the experiment, we scanned a free-running laser diode with an estimated linewidth of 50 MHz across the pressurebroadened (and pressure-shifted) resonances in the isotopically purified 87 Rb cell.…”

Optically polarizedHe3

“…The 3 He density is determined at the time a cell is filled with gas. For SEOP cells the density can also be determined after the cell is filled from the width and/or shift of the alkali-metal absorption lines (Kluttz et al , 2013; Romalis et al , 1997). For SEOP electron-scattering targets, the two methods of determining the density have been reported to agree within 2% (Romalis and Cates, 1998) and 1% (Singh et al , 2015).…”

“…Since SEOP cells contain both 3 He and N 2 gas, the pressure width and/or shift coefficients for both gases are required, although the shift and width is typically dominated by the 3 He gas. These coefficients were measured for the Rb D 1 and D 2 lines with a typical accuracy of 2% (Romalis et al , 1997), and more recently for both Rb and K with a typical accuracy for the width coefficient of 1% (Kluttz et al , 2013). For neutron transmission, the density is replaced with the opacity, which is determined from the transmission through an unpolarized cell.…”

“…A number of factors such as absorption by optically thick alkali-metal vapor, focusing and/or distortion of the laser light by non-uniform blown glass cells, and in some cases poor spatial mode quality make it difficult to realize the goal of uniform optical pumping rate at all points in the cell, which can be partially addressed by pumping from opposing directions (Chann et al , 2003; Chen et al , 2014a). The absorption width of the Rb vapor is determined by pressure broadening of 0.038 nm/bar (Kluttz et al , 2013; Romalis et al , 1997), so the atomic pressure broadened width is comparable to the laser linewidth for high density (10 amg 2 ) targets but substantially smaller than the laser linewidth for typical neutron spin filters (1.5 amg). The degree of the circular polarization (99% or better is usually attained with commercial wave plates) is not highly critical because the relatively high alkali-metal density strongly absorbs the undesired photon spin state (Bhaskar et al , 1979; Chann et al , 2002b).…”