Infrared absorbance spectra were obtained from a dry BeF2glass surface, and from the same surface after exposure to moist air. No absorbance resulted from the dry surface, but an intense, broad, structured contour having maximum absorbance near 3170plusmn;20 cmminus;1was produced by the wetted surface. Continuous evaporation for 905 days at 15 mTorr and room temperature was then carried out, as the integrated absorbance of the 3170 cmminus;1contour was measured relative to the intense, sharp 3690plusmn;5 cmminus;1absorbance from internal Bendash;OH groups. The 3170 cmminus;1contour is thought to arise from the combined stretching vibrations of surface Bendash;OHsdot;sdot;sdot;Fminus;sdot;sdot;sdot;Hndash;OH+2(H2O)2(H2O)nunits. In these, the primary hydration sphere of H3O+contains two H2O molecules and one Fminus;ion, all strongly bound, and the second hydration sphere contains up to six H2O molecules,nle;6. Upon evacuation, the secondhyphen;sphere H2O molecules are removed consecutively, but the two primaryhyphen;sphere H2O molecules, and the very strong Fminus;sdot;sdot;sdot;H hydrogen bond are unaffected. The relative integrated 3170 cmminus;1absorbanceATwas observed to decrease at a decreasing rate by a factor of about 2.5 after 50 days of pumping, and then to decline to sim;20percnt; of thet=0 absorbance, upon pumping for 905 days. The temporal behavior ofAwas found to fit firsthyphen;order kinetics of the form minus;(dA/dt)=lsqb;0.244thinsp;045/(1+t)rsqb;A. Here, lsqb;0.244thinsp;045/(1+t)rsqb;=Bthinsp;exp(minus;sim;(Dgr;H)/RT), whereB=9.65times;105dminus;1at 298.15 K. sim;(Dgr;H) is the specieshyphen;dependent, and therefore timehyphen;dependent, enthalpy in calthinsp;molminus;1, andtis the pumping time in days.
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