title: Absolute photoionization cross-section of the propargyl radical.
abstract: Using synchrotron-generated vacuum-ultraviolet radiation and multiplexed time-resolved photoionization mass spectrometry we have measured the absolute photoionization cross-section for the propargyl (C(3)H(3)) radical, σ(propargyl) (ion)(E), relative to the known absolute cross-section of the methyl (CH(3)) radical. We generated a stoichiometric 1:1 ratio of C(3)H(3):CH(3) from 193 nm photolysis of two different C(4)H(6) isomers (1-butyne and 1,3-butadiene). Photolysis of 1-butyne yielded values of σ(propargyl)(ion)(10.213 eV)=(26.1±4.2) Mb and σ(propargyl)(ion)(10.413 eV)=(23.4±3.2) Mb, whereas photolysis of 1,3-butadiene yielded values of σ(propargyl)(ion)(10.213 eV)=(23.6±3.6) Mb and σ(propargyl)(ion)(10.413 eV)=(25.1±3.5) Mb. These measurements place our relative photoionization cross-section spectrum for propargyl on an absolute scale between 8.6 and 10.5 eV. The cross-section derived from our results is approximately a factor of three larger than previous determinations.
authors.affiliation: Sandia National Laboratories, Combustion Research Facility, Livermore, California 94551, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Savee
authors.forename: Satchin
authors.initials: S
authors.lastname: Soorkia
authors.forename: Oliver
authors.initials: O
authors.lastname: Welz
authors.forename: Talitha M
authors.initials: TM
authors.lastname: Selby
authors.forename: Craig A
authors.initials: CA
authors.lastname: Taatjes
authors.forename: David L
authors.initials: DL
authors.lastname: Osborn