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Growth of nitric acid hydrates on thin sulfuric acid films
Author(s) -
Iraci Laura T.,
Middlebrook Ann M.,
Wilson Margaret A.,
Tolbert Margaret A.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl00916
Subject(s) - sulfuric acid , nitric acid , nucleation , sulfate , crystallization , inorganic chemistry , thin film , materials science , mineralogy , chemistry , analytical chemistry (journal) , organic chemistry , nanotechnology , metallurgy
Type I polar stratospheric clouds (PSCs) are thought to nucleate and grow on stratospheric sulfate aerosols (SSAs). To model this system, thin sulfuric acid films were exposed to water and nitric acid vapors (1 ‐ 3 × 10 −4 Torr H 2 O and 1 ‐ 2.5 × 10 −6 Torr HNO 3 ) and subjected to cooling and heating cycles. FTIR spectroscopy was used to probe the phase of the sulfuric acid and to identify the HNO 3 /H 2 O films that condensed. Nitric acid trihydrate (NAT) was observed to grow on crystalline sulfuric acid tetrahydrate (SAT) films. NAT also condensed in/on supercooled H 2 SO 4 films without causing crystallization of the sulfuric acid. This growth is consistent with NAT nucleation from ternary solutions as the first step in PSC formation.