Gas-Phase Fluorescence Excitation and Emission Spectroscopy of Three Xanthene Dyes (Rhodamine 575, Rhodamine 590 and Rhodamine 6G) in a Quadrupole Ion Trap Mass Spectrometer |
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Authors: | Matthew W Forbes Rebecca A Jockusch |
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Institution: | (1) Department of Chemistry, University of Toronto, Toronto, ON, M5S 3H6, Canada; |
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Abstract: | The gas-phase fluorescence excitation, emission and photodissociation characteristics of three xanthene dyes (rhodamine 575,
rhodamine 590, and rhodamine 6G) have been investigated in a quadrupole ion trap mass spectrometer. Measured gas-phase excitation
and dispersed emission spectra are compared with solution-phase spectra and computations. The excitation and emission maxima
for all three protonated dyes lie at higher energy in the gas phase than in solution. The measured Stokes shifts are significantly
smaller for the isolated gaseous ions than the solvated ions. Laser power-dependence measurements indicate that absorption
of multiple photons is required for photodissociation. Redshifts and broadening of the dispersed fluorescence spectra at high
excitation laser power provide evidence of gradual heating of the ion population, pointing to a mechanism of sequential multiple-photon
activation through absorption/emission cycling. The relative brightness in the gas phase follows the order R575(1.00) < R590(1.15) < R6G(1.29).
Fluorescence emission from several mass-selected product ions has been measured. |
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