The upward flux densities of gaseous ammonia and particulate ammonium through a layer 400 m above ground were determined by aircraft measurements over a rural area in Western Germany. The flux densities were calculated according to the gradient method. The fluxes amounted to 118 k 49 pg/m2h NH,-N and 93 f 47 pg/m2h NH:-N in summer and to 7 k 14 pg/m2h NH,-N and 23 f 34 pg/m2h NHi-N in winter.When integrated over a year, the sum of these ammonia fluxes can be maintained by NH, volatilization from domestic animal excrements. The NH, liberation from mineral fertilizer and natural soils contributes only a small amount to the overall production rate. Most of the NH, and NH: diffusing upwards into the middle troposphere will eventually be incorporated in rain. For the conversion of gaseous NH, to particulate NH: in the first 400 m of the atmosphere a lower limit for a pseudo first-order reaction rate constant of 1-2 x s-I was deduced from flux density considerations.

Energy transfer in the excited state of molecules including quenching, rotational and vibrational energy transfer, and polarization scrambling is one of the major factors which limit the accuracy of laser-induced fluorescence (LIF) measurements. In this contribution, we present time-, wavelength-, and polarization-resolved spectra of OH in a stoichiometric H2/air flame at atmospheric pressure. Emphasis is placed on the investigation of the role of polarization effects and of multi-quantum vibrational energy transfer on fluorescence spectra originating from the OH A2sigma+ state. Results are compared to simulations using a rate-equation model (LASKIN) developed in our group.

The upward flux densities of gaseous ammonia and particulate ammonium through a layer 400 m above ground were determined by aircraft measurements over a rural area in Western Germany. The flux densities were calculated according to the gradient method. The fluxes amounted to 118 ± 49 μg/m2h NH3‐N and 93 ± 47 μg/m2h NH+4‐N in summer and to 7 ± 14 μg/m2h NH3‐N and 23 ± 34 μg/m2h NH+4‐N in winter. When integrated over a year, the sum of these ammonia fluxes can be maintained by NH3 volatilization from domestic animal excrements. The NH3 liberation from mineral fertilizer and natural soils contributes only a small amount to the overall production rate. Most of the NH3 and NH+4 diffusing upwards into the middle troposphere will eventually be incorporated in rain. For the conversion of gaseous NH3 to particulate NH+4 in the first 400 m of the atmosphere a lower limit for a pseudo first‐order reaction rate constant of 1–2 × 10−5 s−1 was deduced from flux density considerations.

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Collision-induced processes (quenching, rotational and vibrational energy transfer, polarization scrambling) affect most LIF experiments. For OH, CH and NO, these processes are studied with picosecond resolution. Methods to obtain quench-free data and implications for flame measurements are discussed.