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Title: Bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ICE multilayers

Abstract

Heterogeneous reactions on polar stratospheric cloud (PSC) particles, composed of ice (Type II PSC) and HNO{sub 3} hydrates (Type I PSC), play a critical role in the depletion of ozone in Antarctic regions. The dynamical nature of ice may affect these reactions and our understanding of chemistry on PSCs. The bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ice multilayers grown epitaxially on Ru(001) were measured utilizing a novel technique of isothermal desorption/depth profiling combined with laser induced thermal desorption (LITD) probing. The measured bulk diffusion constants for HDO into single-crystal H{sub 2}{sup 16}O ice multilayers ranged from D(HDO)=4.2x10{sup -14}{plus_minus}0.3 cm{sup 2}s{sup -1} at T=153 K to D(HDO)=9.0x10{sup -14{plus_minus}0.6} cm{sup 2}s{sup -1} at T=170 K. The bulk diffusion coefficients for H{sub 2}{sup 18}O in crystalline ice varied from D(H{sub 2}{sup 18}O)= 4.4x10{sup -16{plus_minus}0.2} cm{sup 2}s{sup -1} to 5.0x10{sup -15{plus_minus}0.2} cm{sup 2}s{sup -1} over the temperature range T=155-165 K. An Arrhenius analysis of the HDO and H{sub 2}{sup 18}O bulk diffusion coefficients yielded the bulk diffusion activation energies (E{sub A}) and preexponential factors (D{sub o}):E{sub A} (HDO)=2.0{plus_minus}1.0 kcalmol{sup -1}, D{sub o}(HDO)=8.7x10{sup -11{plus_minus}0.6} cm{sup 2}, E{sub A}(H{sub 2}{sup 18}O)= 13.1{plus_minus}0.5 kcalmol{sup -1}, D{sub o}(H{sub 2}{sup 18}O)=9.0x10{sup 2{plus_minus}0.3}more » cm{sup 2}s{sup -1}. The activation barrier for molecular diffusion is consistent with the breakage of two hydrogen bonds. The smaller barrier for HDO diffusion suggests H/D exchange with possible tunneling. The bulk diffusion coefficients predicted at stratospheric temperatures indicate that the ice surfaces are dynamic with diffusion into the bulk competitive with thermal desorption.« less

Authors:
; ;  [1]
  1. Univ. of Colorado, Boulder, CO (United States)
Publication Date:
OSTI Identifier:
370000
Report Number(s):
CONF-960376-
TRN: 96:003805-0049
Resource Type:
Conference
Resource Relation:
Conference: Spring national meeting of the American Chemical Society (ACS), New Orleans, LA (United States), 24-28 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of 211th ACS national meeting; PB: 2284 p.
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; NITRIC ACID; ATMOSPHERIC CHEMISTRY; DEUTERIUM COMPOUNDS; DIFFUSION; WATER; ANTARCTIC REGIONS; HYDRATES; ICE; OZONE; OXYGEN 18; OXYGEN 16; ACTIVATION ENERGY; MONOCRYSTALS; DESORPTION

Citation Formats

Livingston, F E, Whipple, G C, and Brown, D E. Bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ICE multilayers. United States: N. p., 1996. Web.
Livingston, F E, Whipple, G C, & Brown, D E. Bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ICE multilayers. United States.
Livingston, F E, Whipple, G C, and Brown, D E. Tue . "Bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ICE multilayers". United States.
@article{osti_370000,
title = {Bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ICE multilayers},
author = {Livingston, F E and Whipple, G C and Brown, D E},
abstractNote = {Heterogeneous reactions on polar stratospheric cloud (PSC) particles, composed of ice (Type II PSC) and HNO{sub 3} hydrates (Type I PSC), play a critical role in the depletion of ozone in Antarctic regions. The dynamical nature of ice may affect these reactions and our understanding of chemistry on PSCs. The bulk diffusion of HDO and H{sub 2}{sup 18}O into single-crystal H{sub 2}{sup 16}O ice multilayers grown epitaxially on Ru(001) were measured utilizing a novel technique of isothermal desorption/depth profiling combined with laser induced thermal desorption (LITD) probing. The measured bulk diffusion constants for HDO into single-crystal H{sub 2}{sup 16}O ice multilayers ranged from D(HDO)=4.2x10{sup -14}{plus_minus}0.3 cm{sup 2}s{sup -1} at T=153 K to D(HDO)=9.0x10{sup -14{plus_minus}0.6} cm{sup 2}s{sup -1} at T=170 K. The bulk diffusion coefficients for H{sub 2}{sup 18}O in crystalline ice varied from D(H{sub 2}{sup 18}O)= 4.4x10{sup -16{plus_minus}0.2} cm{sup 2}s{sup -1} to 5.0x10{sup -15{plus_minus}0.2} cm{sup 2}s{sup -1} over the temperature range T=155-165 K. An Arrhenius analysis of the HDO and H{sub 2}{sup 18}O bulk diffusion coefficients yielded the bulk diffusion activation energies (E{sub A}) and preexponential factors (D{sub o}):E{sub A} (HDO)=2.0{plus_minus}1.0 kcalmol{sup -1}, D{sub o}(HDO)=8.7x10{sup -11{plus_minus}0.6} cm{sup 2}, E{sub A}(H{sub 2}{sup 18}O)= 13.1{plus_minus}0.5 kcalmol{sup -1}, D{sub o}(H{sub 2}{sup 18}O)=9.0x10{sup 2{plus_minus}0.3} cm{sup 2}s{sup -1}. The activation barrier for molecular diffusion is consistent with the breakage of two hydrogen bonds. The smaller barrier for HDO diffusion suggests H/D exchange with possible tunneling. The bulk diffusion coefficients predicted at stratospheric temperatures indicate that the ice surfaces are dynamic with diffusion into the bulk competitive with thermal desorption.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1996},
month = {10}
}

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