Crystallization Kinetics and Excess Free Energy of H<sub>2</sub>O and D<sub>2</sub>O Nanoscale Films of Amorphous Solid Water

Smith, R. Scott; Matthiesen, J.; Knox, Jake R.; Kay, Bruce D.

doi:10.1021/jp110297q

Cited by 84 publications

(157 citation statements)

References 79 publications

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“…Since the pre-exponential factor is not reported in Baragiola et al (2009) it is not possible to comment on the small difference in the crystallization activation energy. Moreover, Mate et al (2012) found that if the crystallization rate constants for ASW ice deposited at different temperatures were the same, the Avrami n parameters would be different, close to 1 for ice samples generated at 14 K. Extrapolating Smith et al (2011) data at 100 K gives a crystallization rate of 10 13 s −1 , which is close to our measurement range for diffusion at this temperature. Jenniskens et al (1995) demonstrated the phase change between the high-density amorphous ice (I ah ) obtained after deposition at 15 K and the lowdensity amorphous ice (I al ).…”

Section: Measurement Of the Asw Ice Film Reorganization Ratesupporting

confidence: 84%

“…We have extended the works of Mate et al (2012), Smith et al (2011) and Baragiola et al (2009) at lower temperatures using FTIR spectroscopy. We have deposited an ASW film at 15 K, set the ice film to a fixed temperature between 40 and 150 K, and monitored the change in the OH stretch band whose band shape is very sensitive to crystallization (Smith et al 2011), in order to measure the ASW crystallization kinetics.…”

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 70%

“…The ASW ice to crystalline ice kinetics has been studied on 100 ML films (Smith et al 2011) and on interstellar ice analogues (Baragiola et al 2009) for temperatures down to 135 K using an Avrami equation…”

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 99%

“…For a homogeneous threedimension growth, the value of 4 is usually adopted. Smith et al (2011) derived a crystallization rate constant of k cryst = (1.2 ± 0.5) × 10 21 s −1 × exp − 65.5±0.5 kJ mol −1 RT using IR spectroscopy (and (7.3 ± 2.6) × 10 21 s −1 × exp − 68.2±0.5 kJ mol −1 RT using temperature programmed desorption experiments), while Baragiola et al (2009) derived a 59.4 ± 2.2 kJ mol −1 crystallization activation energy on a 300 nm thick ice films. Since the pre-exponential factor is not reported in Baragiola et al (2009) it is not possible to comment on the small difference in the crystallization activation energy.…”

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 99%

“…We have deposited an ASW film at 15 K, set the ice film to a fixed temperature between 40 and 150 K, and monitored the change in the OH stretch band whose band shape is very sensitive to crystallization (Smith et al 2011), in order to measure the ASW crystallization kinetics. The fixed temperature time evolution of the OH stretch band difference spectrum, i.e., the spectrum at time t minus the spectrum at time t = 0 s, is displayed in Fig.…”

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 99%

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Diffusion measurements of CO, HNCO, H₂CO, and NH₃in amorphous water ice

Mispelaer¹,

Theulé²,

Aouididi³

et al. 2013

A&A

115

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Context. Water is the major component of the interstellar ice mantle. In interstellar ice, chemical reactivity is limited by the diffusion of the reacting molecules, which are usually present at abundances of a few percent with respect to water. Aims. We want to study the thermal diffusion of H 2 CO, NH 3 , HNCO, and CO in amorphous water ice experimentally to account for the mobility of these molecules in the interstellar grain ice mantle. Methods. In laboratory experiments performed at fixed temperatures, the diffusion of molecules in ice analogues was monitored by Fourier transform infrared spectroscopy. Diffusion coefficients were extracted from isothermal experiments using Fick's second law of diffusion. Results. We measured the surface diffusion coefficients and their dependence with the temperature in porous amorphous ice for HNCO, H 2 CO, NH 3 , and CO. They range from 10 −15 to 10 −11 cm 2 s −1 for HNCO, H 2 CO, and NH 3 between 110 K and 140 K, and between 5-8 × 10 −13 cm 2 s −1 for CO between 35 K and 40 K. The bulk diffusion coefficients in compact amorphous ice are too low to be measured by our technique and a 10 −15 cm 2 s −1 upper limit can be estimated. The amorphous ice framework reorganization at low temperature is also put in evidence. Conclusions. Surface diffusion of molecular species in amorphous ice can be experimentally measured, while their bulk diffusion may be slower than the ice mantle desorption kinetics.

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Section: Measurement Of the Asw Ice Film Reorganization Ratesupporting

confidence: 84%

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 70%

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 99%

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 99%

Section: Measurement Of the Asw Ice Film Reorganization Ratementioning

confidence: 99%

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