Experimental study of the effect of temperature on ion cluster formation using ion mobility spectrometry

• Published in: Atmospheric research Vol. 90; no. 2; pp. 115 - 124
• Main Authors: Viitanen, A.-K., Mattila, T., Mäkelä, J.M., Marjamäki, M., Anttalainen, O., Keskinen, J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2008; Elsevier
• Subjects: Chemical composition and interactions. Ionic interactions and processes; Earth, ocean, space; Exact sciences and technology; External geophysics; Ion clusters; Ion mobility spectrometry; Meteorology; Particles and aerosols; Time-of-flight, Ion induced nucleation, proton affinity; Time-of-flight, Ion induced nucleation, proton affinity; Ion clusters; Ion mobility spectrometry; experimental studies; Ion clusters; Ion mobility spectrometry; Time-of-flight; Ionic cluster; esters; aerosols; Temperature effect; alcohols; Propanol; Organic ion; Oligomer; troposphere; proton affinity; Ion induced nucleation; nucleation; Atmospheric chemistry; Ion mobility; Ion spectrometry; protons; Formation mechanism
• ISSN: 0169-8095; 1873-2895
• DOI: 10.1016/j.atmosres.2007.12.003

Ion mobility spectrometry offers a robust and effective technique to study ion clusters in ambient conditions. Here, we have experimentally studied the influence of temperature on the positive ion cluster formation of 2-propanol vapor in air, along with parallel measurements for n-butyl acetate vapor in air. For both of these low proton affinity compounds in the ppm concentration range, temperatures below 0 °C tend to favor formation of dimers and trimers. The measurements indicate that approximate estimations for the fractions of these n-mers ( n > 1) in the ion spectra, can be obtained by classical theory for ion induced nucleation. Presence of natural background vapors however slightly blurs the data, especially for the fraction of monomers, so that accurate prediction of the fractions of n-mers in the spectra would require more accurate information on the gas composition. The findings concerning thermal behavior of ions help to understand better ion phenomena also in field conditions.