title: Laser-induced fluorescence from N2(+) ions generated by a corona discharge in ambient air.
abstract: In this work, we present the measurement of laser-induced fluorescence from N2(+) ions via the B(2)Σu(+)-X(2)Σg(+) band system in the near-ultraviolet. The ions were generated continuously by a plasma glow discharge in low pressure N2 and by a corona discharge in ambient air. The fluorescence decay time was found to rapidly decrease with increasing pressure leading to an extrapolated decay rate of ≍10(10) s(-1) at atmospheric pressure. In spite of this quenching, we were able to observe laser induced fluorescence in ambient air by means of a time-gated spectral measurement. In the process of comparing the emission signal with that of N2 spontaneous Raman scattering, ion concentrations in ambient air of order 10(8-)10(10) cm(-3) were determined. With moderate increases in laser power and collection efficiency, ion concentrations of less than 10(6) cm(-3) may be measurable, potentially enabling applications in atmospheric standoff detection of ionizing radiation from hazardous radioactive sources.
authors.affiliation: Department of Physics, University of South Florida, Tampa, FL 33620 USA.
authors.forename: Kumarasiri
authors.initials: K
authors.lastname: Konthasinghe
authors.forename: Kristin
authors.initials: K
authors.lastname: Fitzmorris
authors.forename: Manoj
authors.initials: M
authors.lastname: Peiris
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Hopkins
authors.forename: Benjamin
authors.initials: B
authors.lastname: Petrak
authors.forename: Dennis K
authors.initials: DK
authors.lastname: Killinger
authors.forename: Andreas
authors.initials: A
authors.lastname: Muller