Prototype for in situ detection of atmospheric NO3 and N2O5 via laser-induced fluorescence.
We describe a prototype designed for in situ detection of the nitrate radical (NO3) by laser-induced fluorescence (LIF) and of N2O5 by thermal dissociation followed by LIF detection of NO3. An inexpensive 36 mW continuous wave multi-mode diode laser at 662 nm is used to excite NO3 in the B2E'(0000) <-- X2A'2(0000) band. Fluorescence is collected from 700 to 750 nm. The prototype has a sensitivity to NO3 of 76 ppt for a 60 s integration with an accuracy of 8%. Although this sensitivity is adequate for studies of N205 in many environments, it is much less sensitive (about 300 times) than expected based on a comparison of previously measured photophysical properties of NO2 and NO3. This implies much stronger nonradiative coupling of electronic states in NO3 than in NO2.
Wood
Ezra C
EC
Department of Chemistry, University of California, Berkeley, California 94720, USA.
Wooldridge
Paul J
PJ
Freese
Jens H
JH
Albrecht
Tim
T
Cohen
Ronald C
RC
D004784:Environmental Monitoring / Q000379:methods*; D004867:Equipment Design; D005453:Fluorescence; D007834:Lasers; D009566:Nitrates / Q000032:analysis*; D009589:Nitrogen Oxides / Q000032:analysis*; D012680:Sensitivity and Specificity
D009566:Nitrates; D009589:Nitrogen Oxides; C010125:nitrogen pentoxide