Abstract
This review summarizes some recent experiments with ice nanoparticles (large water clusters) in molecular beams and outlines their atmospheric relevance: (1) Investigation of mixed water–nitric acid particles by means of the electron ionization and sodium doping combined with photoionization revealed the prominent role of HNO3 molecule as the condensation nuclei. (2) The uptake of atmospheric molecules by water ice nanoparticles has been studied, and the pickup cross sections for some molecules exceed significantly the geometrical sizes of the ice nanoparticles. (3) Photodissociation of hydrogen halides on water ice particles has been shown to proceed via excitation of acidically dissociated ion pair and subsequent biradical generation and H3O dissociation. The photodissociation of CF2Cl2 molecules in clusters is also mentioned. Possible atmospheric consequences of all these results are briefly discussed.
Highlights
The fact that small atmospheric ice particles and aerosols are important players in atmospheric chemistry has been recognized and outlined in textbooks, e.g., Finlayson-Pitts and Pitts (2000), and numerous review articles, e.g., Peter (1997); Ravishankara (1997); Finlayson-Pitts (2009); and Vaida (2011)
This review summarizes some recent experiments with ice nanoparticles in molecular beams and outlines their atmospheric relevance: (1) Investigation of mixed water–nitric acid particles by means of the electron ionization and sodium doping combined with photoionization revealed the prominent role of HNO3 molecule as the condensation nuclei
The Na-doping experiments below revealed another important property of mixed HNO3water clusters: the HNO3 molecule is an effective nucleation center around which the clusters start to grow
Summary
The fact that small atmospheric ice particles and aerosols are important players in atmospheric chemistry has been recognized and outlined in textbooks, e.g., Finlayson-Pitts and Pitts (2000), and numerous review articles, e.g., Peter (1997); Ravishankara (1997); Finlayson-Pitts (2009); and Vaida (2011). The individual particles can be investigated under controlled conditions in vacuum by various means: e.g., ionization (electron, photon) and mass spectrometry (MacTaylor and Castleman, 2000; Lengyel et al, 2012b); infrared (IR) spectroscopy (Yacovitch et al, 2011, 2012; Preston et al, 2012; Fujii and Mizuse, 2013) or ultraviolet (UV) photodissociation experiments (Kreher et al, 1999; Li and Huber, 2001; Poterya et al, 2007, 2008a, 2011; Oncák et al, 2008, 2011); particle (electron, photon, neutron) scattering (Heath et al, 2003; Kim et al, 2004; Manka et al, 2012); special methods such as sodium doping and subsequent spectroscopies (Bobbert et al, 2002; Yoder et al, 2011; Pradzynski et al, 2012) Such experiments provide unprecedented molecular-level insight into the small particle generation, their (photo)chemistry and (photo)physics and detailed dynamics of the processes on/in these particles. Some of the methods of aerosol particle spectroscopy have been reviewed in recent book (Signorell and Reid, 2011)
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