Hietala, Paula

Jokinen, Tuija

Junninen, Heikki

Kupiainen-Määttä, Oona

Kurten, Theo Christian

Ruusuvuori, Kai Ilmari

Sipilä, Mikko Juhani

Vehkamäki, Hanna

Atmospheric Measurement Techniques Discussions

Abstract. Sulphuric acid is generally considered one of the most important substances taking part in atmospheric particle formation. However, in typical atmospheric conditions in the lower troposphere sulphuric acid and water alone are unable to form particles. It has been suggested that strong bases may stabilize sulphuric acid clusters so that particle formation may occur. More to the point, amines – strong organic bases – have become the subject of interest as possible cause for such stabilisation. To probe whether amines play a role in atmospheric nucleation, we need to be able to measure accurately the gas-phase amine vapour concentration. Such measurements often include charging the neutral molecules and molecular clusters in the sample. Since amines are bases, the charging process should introduce a positive charge. This can be achieved for example using a positively charged reagent with a suitable proton affinity. In our study, we have used quantum chemical methods combined with a cluster dynamics code to study the use of acetone as a reagent in chemical ionization and compared the results with measurements performed with a chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF). The computational results indicate that protonated acetone is an effective reagent in chemical ionization. However, in the experiments the charger ions were not depleted at the predicted dimethylamine concentrations, indicating that either the modelling scheme or the experimental results – or both – contain unidentified sources of error.
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K. Ruusuvuori

P. Hietala

O. Kupiainen-Määttä

T. Jokinen

H. Junninen

M. Sipilä

T. Kurtén

H. Vehkamäki

Crossref

The charging of neutral dimethylamine and dimethylamine-sulphuric acid clusters using protonated acetone

Helsingin yliopiston digitaalinen arkisto

The charging of neutral dimethylamine and dimethylamine-sulphuric acid clusters using protonated acetone

Abstract

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Helsingin yliopiston digitaalinen arkisto