Experimental Study of the Mesospheric Removal of NF sub(3) by Neutral Meteoric Metals and Lyman- alpha Radiation

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2014-06, Vol.118 (23), p.4120-4129-4120-4129
• Main Authors: Totterdill, Anna, Martin, JCGomez, Kovacs, Tamas, Feng, Wuhu, Plane, John MC
• Format: Article
• Language: English
• Subjects: Ablation; Absorption cross sections; Air pollution; Atmospherics; Capture cross sections; Global warming; Mesosphere; Photolysis
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp503003e

NF sub(3) is a potent anthropogenic greenhouse gas with increasing industrial usage. It is characterized by a large global warming potential due in part to its large atmospheric lifetime. The estimated lifetime of about 550 years means that potential mesospheric destruction processes of NF sub(3) should also be considered. The reactions of NF sub(3) with the neutral metal atoms Na, K, Mg and Fe, which are produced by meteoric ablation in the upper mesosphere, were therefore studied. The observed non-Arrhenius temperature dependences of the reactions between about 190 and 800 K are interpreted using quantum chemistry calculations of the relevant potential energy surfaces. The NF sub(3) absorption cross section at the prominent Lyman- alpha solar emission line (121.6 nm) was determined to be (1.59 plus or minus 0.10)x10 super(-18) cm super(2) molecule super(-1) (at 300 K). In the mesosphere above 60 km, Lyman- alpha photolysis is the dominant removal process of NF sub(3); the reactions with K and Na are 1-2 orders of magnitude slower. However, the atmospheric lifetime of NF sub(3) is largely controlled by reaction with O( super(1)D) and photolysis at wavelengths shorter than 190 nm; these processes dominate below 60 km.