TY - JOUR
T1 - Soft ionization of thermally evaporated hypergolic ionic liquid aerosols
AU - Koh, Christine J.
AU - Liu, Chen Lin
AU - Harmon, Christopher W.
AU - Strasser, Daniel
AU - Golan, Amir
AU - Kostko, Oleg
AU - Chambreau, Steven D.
AU - Vaghjiani, Ghanshyam L.
AU - Leone, Stephen R.
PY - 2011/5/12
Y1 - 2011/5/12
N2 - Isolated ion pairs of a conventional ionic liquid, 1-Ethyl-3-Methyl- Imidazolium Bis(trifluoromethylsulfonyl)imide ([Emim+][Tf 2N-]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim+][Dca-]), are generated by vaporizing ionic liquid submicrometer aerosol particles for the first time; the vaporized species are investigated by dissociative ionization with tunable vacuum ultraviolet (VUV) light, exhibiting clear intact cations, Emim+ and Bmim+, presumably originating from intact ion pairs. Mass spectra of ion pair vapor from an effusive source of the hypergolic ionic liquid show substantial reactive decomposition due to the internal energy of the molecules emanating from the source. Photoionization efficiency curves in the near threshold ionization region of isolated ion pairs of [Emim +][Tf2N-] ionic liquid vapor are compared for an aerosol source and an effusive source, revealing changes in the appearance energy due to the amount of internal energy in the ion pairs. The aerosol source has a shift to higher threshold energy (∼0.3 eV), attributed to reduced internal energy of the isolated ion pairs. The method of ionic liquid submicrometer aerosol particle vaporization, for reactive ionic liquids such as hypergolic species, is a convenient, thermally "cooler" source of isolated intact ion pairs in the gas phase compared to effusive sources.
AB - Isolated ion pairs of a conventional ionic liquid, 1-Ethyl-3-Methyl- Imidazolium Bis(trifluoromethylsulfonyl)imide ([Emim+][Tf 2N-]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim+][Dca-]), are generated by vaporizing ionic liquid submicrometer aerosol particles for the first time; the vaporized species are investigated by dissociative ionization with tunable vacuum ultraviolet (VUV) light, exhibiting clear intact cations, Emim+ and Bmim+, presumably originating from intact ion pairs. Mass spectra of ion pair vapor from an effusive source of the hypergolic ionic liquid show substantial reactive decomposition due to the internal energy of the molecules emanating from the source. Photoionization efficiency curves in the near threshold ionization region of isolated ion pairs of [Emim +][Tf2N-] ionic liquid vapor are compared for an aerosol source and an effusive source, revealing changes in the appearance energy due to the amount of internal energy in the ion pairs. The aerosol source has a shift to higher threshold energy (∼0.3 eV), attributed to reduced internal energy of the isolated ion pairs. The method of ionic liquid submicrometer aerosol particle vaporization, for reactive ionic liquids such as hypergolic species, is a convenient, thermally "cooler" source of isolated intact ion pairs in the gas phase compared to effusive sources.
UR - http://www.scopus.com/inward/record.url?scp=79955856838&partnerID=8YFLogxK
U2 - 10.1021/jp200633b
DO - 10.1021/jp200633b
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C2 - 21506546
AN - SCOPUS:79955856838
SN - 1089-5639
VL - 115
SP - 4630
EP - 4635
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 18
ER -