Setup of the polarization lifetime measurement. Nearly-parallel resonant pump and probe beams perform a relaxation-in-the-dark measurement of the polarization lifetime as pumping is modulated by an optical chopper. A supply of purified helium and a vacuum pump allow control of the buffer gas pressure in the cell.
(a) Polarization data taken at 80 Torr of He that correspond to the data point along the 125 bounces curve shown in (c). (b) Enlarged portion of the data from (a) that shows the fitted curve (light gray, red online) of the sum of two decaying exponentials to extract . (c) Measurements of alkali polarization lifetimes as a function of buffer gas pressure, compared to values predicted by a mathematical model. The lifetime allowed by uncoated surfaces agrees with the model’s prediction for a completely depolarizing surface, while measurements for thick, cross-linked OTS samples agree with predictions for surfaces allowing several hundred bounces.
IR spectroscopy of an OTS monolayer. Indicating the presence of a well-ordered monolayer, DTS and OTS monolayers exhibited similar spectral features at (asymmetric C-H vibrational mode) and (symmetric C-H vibrational mode). The minimal changes in spectral features upon exposure of the film to vapor indicate that the film remains intact.
Reversible temperature dependence of . Data 1 is the first measurement at , data 2 is at , data 3 is cooling to , and data 4 and 5 subsequent heating and cooling to 95 and . Individual data points in each numbered group are repeated measurements with the indicated temperature held constant.
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