Articles | Volume 4, issue 1
Atmos. Meas. Tech., 4, 29–45, 2011
Atmos. Meas. Tech., 4, 29–45, 2011

Research article 19 Jan 2011

Research article | 19 Jan 2011

In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

J. C. Gómez Martín1, J. Blahins2, U. Gross2, T. Ingham3,4, A. Goddard3, A. S. Mahajan1, A. Ubelis2, and A. Saiz-Lopez1 J. C. Gómez Martín et al.
  • 1Laboratory for Atmospheric and Climate Science (CIAC), CSIC, Toledo, Spain
  • 2Institute for Atomic Physics and Spectroscopy (IAPS), University of Latvia, Latvia
  • 3School of Chemistry, University of Leeds, Leeds, UK
  • 4National Centre for Atmospheric Science, School of Chemistry, University of Leeds, UK

Abstract. We demonstrate a new instrument for in situ detection of atmospheric iodine atoms and molecules based on atomic and molecular resonance and off-resonance ultraviolet fluorescence excited by lamp emission. The instrument combines the robustness, light weight, low power consumption and efficient excitation of radio-frequency discharge light sources with the high sensitivity of the photon counting technique. Calibration of I2 fluorescence is achieved via quantitative detection of the molecule by Incoherent Broad Band Cavity-enhanced Absorption Spectroscopy. Atomic iodine fluorescence signal is calibrated by controlled broad band photolysis of known I2 concentrations in the visible spectral range at atmospheric pressure. The instrument has been optimised in laboratory experiments to reach detection limits of 1.2 pptv for I atoms and 13 pptv for I2, for S/N = 1 and 10 min of integration time. The ROFLEX system has been deployed in a field campaign in northern Spain, representing the first concurrent observation of ambient mixing ratios of iodine atoms and molecules in the 1–350 pptv range.