Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques

Abstract

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of anti-relaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10,000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings, in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge X-ray absorption fine structure spectroscopy, and X-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C=C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin anti-relaxation coatings, as well as the design and synthesis of new classes of coating materials.

Laser-pumped paraffin-coated cell rubidium frequency standard

“…Recent work of Seltzer et al 30 on octadecyltrichlorosilane (OTS) shows that the coating can sustain higher temperatures up to 170 C. Surface science techniques help to characterize the quality of the coating materials to the precision of monolayers. 44,45 However, the influence of this coating's temperature coefficient on the clock transition is not yet known and may be expected to have an important impact on the achievable clock stability.…”

Quantum enhanced technologies.

“…However, when atoms bounce off the wall of such a cell, the state of the atom no longer maintains spin coherence. One solution is to use an anti-relaxation coating, such as paraffin [4]. We set up an apparatus to investigate microwave transitions with a variety of cells, coatings, and atomic densities (Fig.…”

Atom Interferometers Warm Up

“…We address this by coating the cell wall with a selfassembled monolayer that preserves the internal quantum state of the atoms throughout collisions [27]. The literature is rich with investigations of various spin-preserving coatings [28][29][30][31][32], but there are none that report having low vapor pressure. We use octyldecyltrichlorosilane as our spin antirelaxation coating due to its high reactivity as compared with other approaches such as octyltrichlorosilane.…”