Intrinsic Properties of Rhodamine B and Fluorescein Gas- phase Ions Studied using Laser-Induced Fluorescence and Photodissociation in a Quadrupole Ion Trap Mass Spectrometer

Studying the intrinsic properties of molecules in the gas-phase is advantageous, since it reduces the complexity present in solution that arises from interactions between the molecule of interest and other species present in the local environment, including those with the solvent itself. In this report, the photophysical properties of gaseous cationic rhodamine B (RBH + ) were determined and photodissociation reaction kinetics and power dependence of three prototropic forms of fluorescein; the cation ([F + H] + ), monoanion ([F H] ), and dianion ([F – 2H] -2 ), each of which possesses their own distinct spectral properties, were measured. The analyte ions of interest were formed via electrospray ionization, mass-selected and stored in a quadrupole ion trap mass spectrometer which has been customized to enable gas-phase spectroscopic studies. Knowledge of the intrinsic photophysical properties of such chromophores in the gas-phase will enable a better understanding of how the local environment of the molecule alters its properties.