Spectroscopic Evidence for the Presence of the v4-Q Branch of Chlorine Nitrate (ClONO2) in Ground-Based Infrared Solar Spectra

The investigation of infrared solar spectra recorded at the lnternational
Scientific Station of the Jungfraujoch, Switzerland, with a high spectral
resolution Fourier transform spectrometer, has revealed an absorption feature
between 780.15 and 780.28 cm-1 which we have identified as the v4-Q branch of
ClONO2 near 780.21 cm-1. While no details of the distribution versus altitude
have been deduced from the data available so far, the analysis of June 1986
observations leads to a mean day-time column density of chlorine nitrate above
the Jungfraujoch, equal to (1.15 +- 0.3) E15 mol./cm2. This value is in good
agreement with recently published ClONO2 results obtained during the ATMOS/SL3
mission at 30°N latitude. The present research represents an important step
towards assessing the possibility of monitoring the telluric ClONO2 column
density from high mountain based stations.