Fundamental mechanisms of He relaxation on glass

We present a model of He relaxation on the surface of borosilicate glass which accurately predicts observed relaxation rates and their temperature dependence. Above room temperature He dissolves into Pyrex, where interactions with Fe3þ ions result in a relaxation time of 1 ms. Gas exchange across the glass surface of an enclosed vessel leads to T 1 1 1⁄4 A=V ð3:9 1:4Þ 10 2 cm/h at room temperature, where A=V is the surface-to-volume ratio. The activation energy for relaxation is 13:7 0:7 kJ/mol and is dominated by the activation energy of He diffusion in glass. This is the first successful confirmation of predicted He relaxation rates in glass vessels. 2003 Elsevier Science B.V. All rights reserved.