Resolution of Individual Component Fluorescence Lifetimes from a Mixture of Trapped Ions by Laser-Induced Fluorescence/Ion Cyclotron Resonance

Abstract

We have measured the fluorescence lifetime (τ) of both pure C6F5H+ and pure C6F3H3+ confined in an open cylindrical (ICR) Penning trap as 44 ± 2 ns and 51 ± 2 ns, respectively, consistent (∼10%) with prior literature values in the absence of ion trapping and magnetic field. For an equimolar mixture of C6F5H+ and C6F3H3+ the effective lifetime, τeff, was 47 ± 2 ns. Ion cyclotron-resonant azimuthal quadrupolar excitation successfully isolated either C6F5H+ or C6F3H3+ ions from the mixture, each with the same fluorescence lifetime as from a pure sample. The signal-to-noise ratio, ∼94:1, demonstrates the feasibility of observing fluorophores of lower quantum yield, such as tryptophan. This work represents the first determination of fluorescence lifetimes of organic ions in a Penning trap, and demonstrates the feasibility of resolving fluorescence from individual species in a chemically heterogeneous mixture by mass-selective ion cyclotron resonance.