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Lyman-α driven molecule formation on SiO2 surfaces—connection to astrochemistry on dust grains in the interstellar medium
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10.1063/1.3532089
/content/aip/journal/jcp/134/6/10.1063/1.3532089
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/6/10.1063/1.3532089

Figures

Image of FIG. 1.
FIG. 1.

Quartz Lyman-α lamp coupled to the infrared cell via a MgF2 window. The mass spectrometer is located as shown.

Image of FIG. 2.
FIG. 2.

Measured distribution of emitted power from Lyman-α source using a thermopile. The distribution shown by the black points is very strongly peaked in the forward direction and estimated to be cos300Θ, as shown by the red angular distribution.

Image of FIG. 3.
FIG. 3.

SiO2 sample pressed into a tungsten grid stretched between two Ni clamps which are cooled by l-N2. The grid is at 45° to Lyman-α radiation and to the incident IR radiation.

Image of FIG. 4.
FIG. 4.

Evolution of associated Si-OH···ON2 bands in the IR spectra during N2O adsorption on clean Si-OH.

Image of FIG. 5.
FIG. 5.

Lyman-α induced decrease in integrated absorbance for N2O(g) (10 Torr, 300 K) modes ν13 and 2ν1. Here only 13% of N2O(g) has been consumed in the experiment.

Image of FIG. 6.
FIG. 6.

Lyman-α photolysis of clean SiO2 containing only isolated Si-OH groups. The factor of 5 in the calculation is due to the approximation that only the outer 1/5 of the SiO2 surfaces receives Lyman-α radiation due to strong absorption and scattering.

Image of FIG. 7.
FIG. 7.

A qualitative comparison of the infrared spectral evolution during the photodecomposition of N2O in the gas phase (300 K) and in the adsorbed phase (71 K). N2O4 species produced by the fragment combination are observed on the SiO2 surface while the gas phase measurements barely detect this species.

Image of FIG. 8.
FIG. 8.

An example of quantitative measurements of the depletion of N2O on the SiO2 surface at 71 K during Lyman-α irradiation in three sequential experiments, I, II, and III. The shutter is alternatively opened and closed thereby turning the light on and off. Loss of absorbance occurs in vacuum by two processes: thermal and thermal + photodesorption of N2O (slopes m0 and m1).

Image of FIG. 9.
FIG. 9.

An example of the production of N2O4, one of the combination products of photodecomposition of N2O adsorbed on SiO2.

Image of FIG. 10.
FIG. 10.

Variation of average complex product enhancement ratio, , with the complexity of the combination products.

Tables

Generic image for table
Table I.

Photodissociation kinetic parameters.

Generic image for table
Table II.

Selectivity of combination processes.

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/content/aip/journal/jcp/134/6/10.1063/1.3532089
2011-02-11
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Lyman-α driven molecule formation on SiO2 surfaces—connection to astrochemistry on dust grains in the interstellar medium
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/6/10.1063/1.3532089
10.1063/1.3532089
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