HR: 1340h
AN: A23B-0940    [Abstracts]
TI: Development of an Instrument for in situ Atmospheric Laser-Induced Fluorescence Measurements of IO Using a Compact all Solid-State Titanium:Sapphire Laser System
AU: * Co, D T
EM: co@fas.harvard.edu
AF: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Lapson, L B
EM: lapson@huarp.harvard.edu
AF: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Hanisco, T F
EM: hanisco@huarp.harvard.edu
AF: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Anderson, J G
EM: anderson@huarp.harvard.edu
AF: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AB: Ozone loss over midlatitudes of the northern hemisphere is well documented in both the scientific literature and the public policy arena. Accurately defining secular trends in the distribution of ozone and establishing the mechanism responsible for the observed losses are two dominant and enduring issues. "Although the chemistry of chlorine and bromine in the stratosphere is reasonably well known, this is not the case for iodine" (WMO, 2002). It was speculated that the observed losses of ozone in the lowermost stratosphere might be due to the presence of IO in the 1 ppt range. While the preponderance of remote observations suggests that IO is probably not a significant contributor to ozone loss, a direct in situ measurement of IO in the lower stratosphere would, as an independent technique, bring considerable closure to this issue. Measuring IO in situ requires the sensitivity to detect sub parts per trillion mixing ratios of IO, which can be obtained with laser-induced fluorescence (LIF) using an approach similar to that of the OH and NO₂ LIF instruments operated in this lab. The IO LIF instrument takes advantage of the very high absorption cross sections of the narrow single rotational lines of IO. Laser excitation is achieved using a frequency doubled, Nd:YAG pumped Ti:sapphire laser system optimized for narrow band operation (0.0008 nm) at 445 nm. Recent advances in solid state Nd:YAG laser technology have resulted in extremely small and efficient lasers. The Nd:YAG laser is only 4" × 7" × 2.5" and weighs less than 4 lbs. The entire optical footprint of the Nd:YAG/Ti:sapphire laser system currently being used is only 12.5" × 12.5" × 5". The overall efficiency of the laser system also allows for smaller power requirements and easier system integration. Fluorescence data of IO and sensitivity estimates of the IO LIF instrument were determined and will be reported.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005