title: Potassium spin polarization lifetime for a 30-carbon chain siloxane film.
abstract: The siloxane film derived from the 30-carbon chain triacontyltrichlorosilane (TCTS) is studied as an anti-relaxation coating for atomic vapor cells. The longitudinal spin relaxation lifetime of optically pumped potassium atoms in the presence of TCTS is measured and the average number of non-relaxing atom-wall collisions, or bounces, enabled by the coated surface is determined. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) of TCTS were performed to investigate changes in chemical states and surface morphology of TCTS arising from K atom deposition on the film surface. TCTS was found to give approximately 530 bounces. Following lifetime measurements, K2p signals were clearly observed in XPS spectra. AFM images display non-preferential K deposition on the TCTS surface, however additional AFM studies with a TCTS surface exposed to Rb atoms show deposition occurs along surface defects. In agreement, Rb is found to preferentially deposit along the step edges of an 18-carbon chain monolayer film derived from 1-Octadecene. Finally, AFM indicates a much smoother surface for a tetracontane coating relative to TCTS. The importance of siloxane surface morphology versus film thickness with respect to coating performance is discussed.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Amber M
authors.initials: AM
authors.lastname: Hibberd
authors.forename: Susanna L
authors.initials: SL
authors.lastname: Bergman
authors.forename: Yu Lin
authors.initials: YL
authors.lastname: Zhong
authors.forename: Steven L
authors.initials: SL
authors.lastname: Bernasek