Fe embedded in ice: The impacts of sublimation and energetic particle bombardment

The fate of meteoric metals in ice particles: Effects of sublimation and energetic particle bombardment

“…The Fe adsorption energy is -306 kJ mol -1 , because the Fe has inserted into a H 2 O molecule to form the very stable HFeOH molecule bound to the surface. This is consistent with the observation of Fe(OH) 2 in the sputtering experiment of Frankland and Plane (2015). Note that in that earlier study we used electronic structure calculations to show that when Fe is bound to an H 2 O trimer, there was a barrier of 70 kJ mol -1 for the Fe to insert into one of the H 2 O molecules.…”

“…These were carried out at the B3LYP/6-311+G level of theory using the Gaussian 09 suite of programs (Frisch et al, 2009). We also include here calculations on Fe adsorbed on ice, in order to compare with our recent experimental study (Frankland and Plane, 2015). Figure 4 shows the optimized structures of Mg, Fe and K adsorbed on a model ice surface consisting of 12 H 2 O molecules arranged in two stacked hexagonal rings.…”

“…However, during the geometry optimization starting with a loosely adsorbed Fe, there was no indication of a barrier to insertion, probably because of additional stabilization from the H 2 O ring structure. After the formation of HFeOH, further rearrangement with an adjacent H 2 O on the surface should produce Fe(OH) 2 + H 2 without a significant activation barrier (see Figure 7 in Frankland and Plane (2015)).…”

“…For Fe, γ Fe also appears close to unity between 135 and 150 K, explaining the significant metal depletion observed in the vicinity of PMCs. More recently it was shown that Fe reacts on the ice surface to form Fe(OH) 2 , and that it is sputtered efficiently from the ice surface by relatively low energy Ar + ions (< 500 eV) ( Frankland and Plane, 2015).…”

Stratospheric aerosol-Observations, processes, and impact on climate

“…Hervig et al [] found that mesospheric ice particles in polar mesospheric clouds can contain over 1% by mass of MSPs. Frankland and Plane [] showed that the subsequent sublimation of the H 2 O ice will leave behind a refractory residue. Impactor sampling in the middle and upper stratosphere showed that the collected solid particles act as nucleation cores for sulfate particles [ Bigg , ].…”