Molecular structure conversion of fluorescein monoanions in an electrostatic storage ring

Journal article, 2012

The photodissociation of fluorescein monoanions was studied by varying the storage times of the ions in an ion trap and an electrostatic storage ring, before laser irradiation. The photodissociation neutral spectra as a function of time vary, in a manner dependent on the storage time as well as the laser wavelength; spectra consist of components with short and long lifetimes. By comparing the wavelength spectra of fluorescein obtained herein with absorption spectra reported recently for the solution and gas phases, it was deduced that the spectra originated from various tautomers of fluorescein monoanions. Moreover, interconversion of these tautomers occurs during long-term storage in the storage ring in vacuo. The wavelength spectra of the converted ions depend strongly on the storage time in the ring. In addition, we have also performed detailed semiempirical quantum-chemical computations, to try revealing what kind of monoanion tautomers we are dealing with.