Measurement of thermal accommodation of spin-polarized hydrogen on a saturatedHe4film at 0.18-0.4 K

The thermal accommodation of H-gas atoms on a saturated superfluid-${}_{}{}^4{}_{}{}^{}\mathrm{He}$-film-covered surface has been measured in the temperature range 0.18-0.4 K. A straightforward stationary-state measuring technique is employed whereby we determine the heat flux conducted by H-gas atoms from a superfluid-${}_{}{}^4{}_{}{}^{}\mathrm{He}$-film-covered bolometer, biased above ambient temperature. The results agree with recent calculations of the thermal-accommodation properties dominated by sticking-evaporation collisions mediated by ripplon creation.