title: Benzylammonium Thermometer Ions: Internal Energies of Ions Formed by Low Temperature Plasma and Atmospheric Pressure Chemical Ionization.
abstract: The extent of internal energy deposition upon ion formation by low temperature plasma and atmospheric pressure chemical ionization was investigated using novel benzylammonium thermometer ions. C-N heterolytic bond dissociation enthalpies of nine 4-substituted benzylammoniums were calculated using CAM-B3LYP/6-311++G(d,p), which was significantly more accurate than B3LYP/6-311++G(d,p), MP2/6-311++G(d,p), and CBS-QB3 for calculating the enthalpies of 20 heterolytic dissociation reactions that were used to benchmark theory. All 4-substituted benzylammonium thermometer ions fragmented by a single pathway with comparable dissociation entropies, except 4-nitrobenzylammonium. Overall, the extent of energy deposition into ions formed by low temperature plasma was significantly lower than those formed by atmospheric pressure chemical ionization under these conditions. Because benzylamines are volatile, this new suite of thermometer ions should be useful for investigating the extent of internal energy deposition during ion formation for a wide range of ionization methods, including plasma, spray and laser desorption-based techniques. Graphical Abstract ᅟ.
authors.affiliation: School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Stephens
authors.affiliation: School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Morphy
authors.initials: M
authors.lastname: Dumlao
authors.affiliation: School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Dan
authors.initials: D
authors.lastname: Xiao
authors.affiliation: School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Daming
authors.initials: D
authors.lastname: Zhang
authors.affiliation: School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia. w.donald@unsw.edu.au.
authors.forename: William A
authors.initials: WA
authors.lastname: Donald
keywords: Atmospheric pressure chemical ionization; Benzylammonium; Benzylpyridinium; Collision induced dissociation; Internal energy distributions; Ion effective temperature; Low temperature plasma ionization; Mass spectrometry; Thermometer ions