Gaseous Diffusion Coefficients

Marrero, T. R.; Mason, Edward A.

doi:10.1063/1.3253094

Cited by 1,065 publications

(480 citation statements)

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“…One could argue, as detailed in Langenfelds et al (2005), that ordinary diffusion is at play. Diffusion coefficients for CO 2 in air have been known for a long time (Kestin et al, 1984;Marrero and Mason, 1972;1973). However, if one calculates the diffusion length, i.e.…”

Section: Resultsmentioning

confidence: 99%

Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

2015

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Abstract.It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i) physisorption and (ii) chemisorption. Physisorption is associated with lower binding energies in the order of 1-10 kJ mol −1 , compared to chemisorption which ranges from 100 to 1000 kJ mol −1 . Furthermore, chemisorption only forms monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws; however, it can be influenced by hysteresis effects. In the present experiment, we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. Our observations from completely decanting one steel and two aluminium cylinders are in agreement with the pressure dependence of physisorption for CO 2 , CH 4 , and H 2 O. The CO 2 results for both cylinder types are in excellent agreement with the pressure dependence of a monolayer adsorption model. However, mole fraction changes due to adsorption on aluminium (< 0.05 and 0 ppm for CO 2 and H 2 O) were significantly lower than on steel (< 0.41 ppm and about < 2.5 ppm, respectively). The CO 2 amount adsorbed (5.8 × 10 19 CO 2 molecules) corresponds to about the fivefold monolayer adsorption, indicating that the effective surface exposed for adsorption is significantly larger than the geometric surface area. Adsorption/desorption effects were minimal for CH 4 and for CO but require further attention since they were only studied on one aluminium cylinder with a very low mole fraction. In the climate chamber, the cylinders were exposed to temperatures between −10 and +50 • C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO 2 , ranging from 0.0014 to 0.0184 ppm • C −1 for steel cylinders and −0.0002 to −0.0003 ppm • C −1 for aluminium cylinders. The reversed temperature dependence for aluminium cylinders points to significantly lower desorption energies than for steel cylinders and due to the small values, they might at least partly be influenced by temperature, permeation from/to sealing materials, and gas-consumptioninduced pressure changes. Temperature coefficients for CH 4 , CO, and H 2 O adsorption were, within their error bands, insignificant. These results do indicate the need for careful selection and usage of gas cylinders for high-precision calibration purposes such as requested in trace gas applications.

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Section: Resultsmentioning

confidence: 99%

Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

2015

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“…with p N 2 (p CO 2 ) the N 2 (CO 2 ) partial pressure and b H 2 O,CO 2 and b H 2 O,air calculated using the data given in Marrero & Mason (1972). The scale heights H H 2 O and H n were calculated using the cold-trap temperature, which was defined as the minimum temperature in the atmosphere (see Section 3).…”

Section: Evolution Of Atmospheric Compositionmentioning

confidence: 99%

WATER LOSS FROM TERRESTRIAL PLANETS WITH CO₂-RICH ATMOSPHERES

Wordsworth

Pierrehumbert

2013

ApJ

193

169

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Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO 2 can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO 2 atmospheric partial pressures (0.1-1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO 2 -rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m −2 (global mean) unlikely to lose more than one Earth ocean of H 2 O over their lifetimes unless they lose all their atmospheric N 2 /CO 2 early on. Because of the variability of H 2 O delivery during accretion, our results suggest that many "Earth-like" exoplanets in the habitable zone may have ocean-covered surfaces, stable CO 2 /H 2 O-rich atmospheres, and high mean surface temperatures.

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“…a The values of D st are calculated for a reference pressure of 10 μbar and temperature of 1100 K. b The coefficients are calculated from Marrero & Mason (1972), apart from H 2 O. The latter coefficient is calculated by using a simple formula in Banks & Kockarts (1973).…”

Section: The Upper and Lower Boundariesmentioning

confidence: 99%

Ionization of Extrasolar Giant Planet Atmospheres

Koskinen

Cho

Achilleos

et al. 2010

ApJ

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Many extrasolar planets orbit close in and are subject to intense ionizing radiation from their host stars. Therefore, we expect them to have strong, and extended, ionospheres. Ionospheres are important because they modulate escape in the upper atmosphere and can modify circulation, as well as leave their signatures, in the lower atmosphere. In this paper, we evaluate the vertical location Z I and extent D I of the EUV ionization peak layer. We find that Z I ≈ 1-10 nbar-for a wide range of orbital distances (a = 0.047-1 AU) from the host star-and D I /H p 15, where H p is the pressure scale height. At Z I , the plasma frequency is ∼80-450 MHz, depending on a. We also study global ion transport, and its dependence on a, using a three-dimensional thermosphere-ionosphere model. On tidally synchronized planets with weak intrinsic magnetic fields, our model shows only a small, but discernible, difference in electron density from the dayside to the nightside (∼9 × 10 13 m −3 to ∼2 × 10 12 m −3 , respectively) at Z I . On asynchronous planets, the distribution is essentially uniform. These results have consequences for hydrodynamic modeling of the atmospheres of close-in extrasolar giant planets.

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Gaseous Diffusion Coefficients

Cited by 1,065 publications

References 0 publications

Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

WATER LOSS FROM TERRESTRIAL PLANETS WITH CO₂-RICH ATMOSPHERES

Ionization of Extrasolar Giant Planet Atmospheres

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Gaseous Diffusion Coefficients

Cited by 1,065 publications

References 0 publications

Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

WATER LOSS FROM TERRESTRIAL PLANETS WITH CO2-RICH ATMOSPHERES

Ionization of Extrasolar Giant Planet Atmospheres

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WATER LOSS FROM TERRESTRIAL PLANETS WITH CO₂-RICH ATMOSPHERES