We discuss the possible role of energy nonaccommodation (monomer-cluster collisions that do not result in stable product formation due to liberated excess energy) in atmospheric nucleation processes involving sulfuric acid. Qualitative estimates of the role of nonaccommodation are computed using quantum Rice-Ramsberger-Kassel theory together with quantum chemically calculated vibrational frequencies and anharmonic coupling constants for small sulfuric acid-containing clusters. We find that energy nonaccommodation effects may, at most, decrease the net formation rate of sulfuric acid dimers by up to a factor of 10 with respect to the hard-sphere collision rate. A decrease in energy nonaccommodation due to an increasing number of internal degrees of freedom may kinetically slightly favor the participation of amines rather than ammonia as stabilizing agents in sulfuric acid nucleation, though the kinetic enhancement factor is likely to be less than three. However, hydration of the clusters (which always occurs in ambient conditions) is likely to increase the energy accommodation factor, reducing the role that energy nonaccommodation plays in atmospheric nucleation.
Bibliographical noteFunding Information:
This research was supported by the Academy of Finland (Project Nos. 1118615 and 1127372) and the Estonian Research Council (Project No. SF0180043s08). P.H.M. and C.K. gratefully acknowledge financial support from the National Science Foundation (Contract Nos. DGE-0114372 and ATM-050067). P.G. gratefully acknowledges hospitality from the University of Helsinki (Dept. of Physics) and financial support from Universidad Complutense de Madrid. Also funding from the Spanish Ministry of Education, Project Nos. FIS2007-6168 and CTQ2008-02578/BQU are acknowledged. We thank the CSC IT Center for Science for computer time.