Alison Michelle Seguin, PhD Candidate

DEPARTMENT OF CHEMISTRY

CHEMISTRY 601/603

ANALYTICAL/ENVIRONMENTAL SECTION

 

SPEAKER:            Alison Michelle Seguin, PhD Candidate

DATE:                     Monday, November 2, 2009

TIME:                      12:00 pm - PLEASE NOTE TIME CHANGE

PLACE:                  SB 324

TITLE:                  "Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO₂, NO and IO by laser-induced fluorescence".   

                                

ABSTRACT:           

The first in situ measurements of concentrations of OH in ambient air using an all-solid-state laser were made by Bloss et al. (2003).    A Nd:YAG-Ti:Sapphire laser system was coupled with a Fluorescence Assay by Gas Expansion (FAGE) instrument in order to detect atmospheric OH, HO₂, IO and NO.  Simultaneous measurements of OH and HO₂ found detection limits on the order of 3.1 x 10⁵ molecules cm^-3 for OH and 2.6 x 10⁶ molecules cm^-3 for HO₂.  OH is highly reactive in the atmosphere and is important in the oxidization and removal of a number of species in the atmosphere. Detection of this radical is of significance to understand atmospheric chemistry and to validate computational oxidation models. 

The theory behind the instrument designed by Bloss et al. (2003) will be investigated in detail, along with the obstacles that had to be overcome. Both advantages and disadvantages of the instrument will be discussed in context of future field studies.

Bloss, W.J., T.J. Gravestock, D.E. Heard, T. Ingham, G.P. Johnson and J.D. Lee, (2003), Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO₂, NO and IO by laser-induced fluorescence, J. Environ. Monit., 5, 21-28.