title: A velocity map imaging photoelectron spectrometer for the study of ultrafine aerosols with a table-top VUV laser and Na-doping for particle sizing applied to dimethyl ether condensation.
abstract: We present a new experimental configuration for the study of size-dependent, angle-resolved photoelectron and photoion spectra of weakly bound ultrafine aerosol particles targeted at particle sizes below ~20 nm. It combines single photon ionization by a tunable, table-top vacuum ultraviolet laser at energies up to 18 eV with velocity map imaging detection and independent size determination of the aerosol particles using the Na-doping method. As an example, the size-dependence of the valence photoelectron spectrum of dimethyl ether clusters and ultrafine aerosols is investigated. Up to a mean particle diameter of ~3-4 nm, the first ionization energy (value at band maximum) decreases systematically (up to ~1 eV) and the corresponding band broadens systematically (up to a factor of ~3) with increasing aggregate size. Plateau values for band positions and bandwidths are reached beyond a diameter of ~3-4 nm. Experimental evidence for the dominance of the fast intermolecular proton transfer over monomer fragmentation reactions upon ionization is presented via photoion imaging.
authors: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
authors: Bruce L
authors: BL
authors: Yoder
authors: Adam H C
authors: AH
authors: West
authors: Bernhard
authors: B
authors: Schläppi
authors: Egor
authors: E
authors: Chasovskikh
authors: Ruth
authors: R
authors: Signorell
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D007834:Lasers; D008738:Methyl Ethers / Q000737:chemistry*; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D012964:Sodium / Q000737:chemistry*; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D000336:Aerosols; D008738:Methyl Ethers; D012964:Sodium; C033413:dimethyl ether